Why the **** did I do that? A build retrospective.
10-13-15, 01:51 AM
#27
Thanks diabolical, I'm glad it's been encouraging.
Is it just the bushing that's different or also the mounting plate? If it's just the bushing then presumable I can simply make a spacer for mine with the proper ID and make a 3rd mold relatively simply. So... if that's the case, what is the manual racks passenger side OD where the bushing sits?
Is it just the bushing that's different or also the mounting plate? If it's just the bushing then presumable I can simply make a spacer for mine with the proper ID and make a 3rd mold relatively simply. So... if that's the case, what is the manual racks passenger side OD where the bushing sits?
10-26-15, 04:51 PM
#28
Just a little update...
Had a bit of time about a week ago and decided to clean up the bushings and I even made one of the molds and tried to use it. The mold turned out very well... However, the chunk of acetal I purchased appears to be the high viscosity variant and as such won't poor out of my melting pot. You live and you learn...
So... Now it looks like when I do have some free time again I'm going to see if I can use the mold I have and make a wax replica of the bushing and mold the bushing out of aluminum using lost wax molding with some green sand.
Had a bit of time about a week ago and decided to clean up the bushings and I even made one of the molds and tried to use it. The mold turned out very well... However, the chunk of acetal I purchased appears to be the high viscosity variant and as such won't poor out of my melting pot. You live and you learn...
So... Now it looks like when I do have some free time again I'm going to see if I can use the mold I have and make a wax replica of the bushing and mold the bushing out of aluminum using lost wax molding with some green sand.
04-12-16, 11:35 PM
#29
It's been quite the few months since I've been particularly active, much less posted anything of note. Long story short, career and location changes tend to mess with ones other plans and pursuits. In short, I can only work on automotive things during the weekends (at best) which has more or less killed my bushing side project. In other car related news I picked up tags for my 7 last weekend and it will likely be drivable this weekend.
Regardless, onto something a bit more useful. I've had a direct inquiry and seen a few threads related to the topic of trans adaptation. Since I've given one person my reference drawings a while back I figured I'd drop them here too.
First things first though. These are not "everything you need to do X" drawings. These are references to general dimensions and specific bolt hole locations to attach a R type trans to a LSx style SBC. These will also work for a general 350 SBC but be missing one bolt hole. For some general notes:
Use hot rolled steel for this.
Check hole size, all of these holes were dimensioned for the specific machine the plates were being cut on. Some are exact, some are not, some are simply used as location markers.
The starter area cut out is not exact, it works, but it you're a perfectionist it will annoy you.
The one plate with the lower area cutout goes against the LSx and is there due due to a variety of pieces that poke beyond the rear engine trans attachment plane.
You will need to make a center piece for the flywheel adapter to hold the pilot bearing, I made mine out of Aluminum and pressed it into the center of the flywheel adapter.
The flywheel adapter must have a step that locates the flywheel.
All of the various flywheel adapter pieces cannot protrude into the inner volume of the flywheel or else you will have clearance issues that will manifest once you try to secure the clutch disc and pressure plate.
You will need to make posts to locate the R type trans.
The oil pan bolts location have some amount of variance. Check yours.
The Red holes are for the LSx. Blue for the RX.
In short, and I cannot emphasize this enough, this is primarily just for those that have the know how to do this work themselves but need accurate hole locations. Most of this info can otherwise be seen in this thread (https://www.rx7club.com/general-rota...sions-1021812/) thanks to Jacob for providing good measurements.
A little added bonus are the little plates in the center. Those plates allowed me to locate two master cylinders in the stock location for my manual brakes setup.
Since I cannot UL .dxf files here, follow the dropbox links for them. If you have questions, let me know.
https://www.dropbox.com/s/nm34berib1...erR12.dxf?dl=0
https://www.dropbox.com/s/2ilphf3nlg...ayout.dxf?dl=0
Regardless, onto something a bit more useful. I've had a direct inquiry and seen a few threads related to the topic of trans adaptation. Since I've given one person my reference drawings a while back I figured I'd drop them here too.
First things first though. These are not "everything you need to do X" drawings. These are references to general dimensions and specific bolt hole locations to attach a R type trans to a LSx style SBC. These will also work for a general 350 SBC but be missing one bolt hole. For some general notes:
Use hot rolled steel for this.
Check hole size, all of these holes were dimensioned for the specific machine the plates were being cut on. Some are exact, some are not, some are simply used as location markers.
The starter area cut out is not exact, it works, but it you're a perfectionist it will annoy you.
The one plate with the lower area cutout goes against the LSx and is there due due to a variety of pieces that poke beyond the rear engine trans attachment plane.
You will need to make a center piece for the flywheel adapter to hold the pilot bearing, I made mine out of Aluminum and pressed it into the center of the flywheel adapter.
The flywheel adapter must have a step that locates the flywheel.
All of the various flywheel adapter pieces cannot protrude into the inner volume of the flywheel or else you will have clearance issues that will manifest once you try to secure the clutch disc and pressure plate.
You will need to make posts to locate the R type trans.
The oil pan bolts location have some amount of variance. Check yours.
The Red holes are for the LSx. Blue for the RX.
In short, and I cannot emphasize this enough, this is primarily just for those that have the know how to do this work themselves but need accurate hole locations. Most of this info can otherwise be seen in this thread (https://www.rx7club.com/general-rota...sions-1021812/) thanks to Jacob for providing good measurements.
A little added bonus are the little plates in the center. Those plates allowed me to locate two master cylinders in the stock location for my manual brakes setup.
Since I cannot UL .dxf files here, follow the dropbox links for them. If you have questions, let me know.
https://www.dropbox.com/s/nm34berib1...erR12.dxf?dl=0
https://www.dropbox.com/s/2ilphf3nlg...ayout.dxf?dl=0
04-19-16, 09:09 PM
#30
A feast after the famine! (not really...)
Given I'm actually driving the car I thought a person or two might be interested in how she currently sits. In general, I'm satisfied with how she currently runs. I've most of the base map done and the parts that aren't done have a good margin in them so lean isn't really an issue. Also, since I have a pretty stock engine I simply stole the base timing map from a stock LS1.
I quite like the mishimoto reflective tape. It seems too stick well which is the main complaint about the DEI tape, then again, I did clean the intake and rough it up too. I noticed ~10*F lowering in my IATs sitting at idle. I am fairly surprised by that considering how much heat the engine puts out (I need to vent the hood). I am also quite happy with my spartan wideband (a lot less hassle and more confidence than my previous innovates) as well as my switch from Wilwood MCs to Tilton.
I had a very good previous experience with EBC brakes and have their Yellow Stuff all the way around and they're performing nicely. However, I'm a little miffed that I had to modify the mounting ears on the rears because they were a bit too long. It didn't take a lot of effort, just ground them down and rounded the edges but frankly, I shouldn't have had to do that with ~$100 (MSRP) brake pads. The fronts on the other hand fit quite well.
First and second gear are next to useless if I get aggressive with the throttle and 3rd is borderline. I imagine 3rd will become useless too once I get a good suspension in it as it's being helped immensely by weight transfer on the stock springs/shocks. Although, despite this (and running no sways) and the semi-boat feeling it entails (compared to my S2000), it has rather good corner speed and I have excellent confidence due to all the feeling from my manual rack conversion.
Attached are a few pics of her sitting at a friends house. The rear is high because it's an incline and resting on the e-brake.
Given I'm actually driving the car I thought a person or two might be interested in how she currently sits. In general, I'm satisfied with how she currently runs. I've most of the base map done and the parts that aren't done have a good margin in them so lean isn't really an issue. Also, since I have a pretty stock engine I simply stole the base timing map from a stock LS1.
I quite like the mishimoto reflective tape. It seems too stick well which is the main complaint about the DEI tape, then again, I did clean the intake and rough it up too. I noticed ~10*F lowering in my IATs sitting at idle. I am fairly surprised by that considering how much heat the engine puts out (I need to vent the hood). I am also quite happy with my spartan wideband (a lot less hassle and more confidence than my previous innovates) as well as my switch from Wilwood MCs to Tilton.
I had a very good previous experience with EBC brakes and have their Yellow Stuff all the way around and they're performing nicely. However, I'm a little miffed that I had to modify the mounting ears on the rears because they were a bit too long. It didn't take a lot of effort, just ground them down and rounded the edges but frankly, I shouldn't have had to do that with ~$100 (MSRP) brake pads. The fronts on the other hand fit quite well.
First and second gear are next to useless if I get aggressive with the throttle and 3rd is borderline. I imagine 3rd will become useless too once I get a good suspension in it as it's being helped immensely by weight transfer on the stock springs/shocks. Although, despite this (and running no sways) and the semi-boat feeling it entails (compared to my S2000), it has rather good corner speed and I have excellent confidence due to all the feeling from my manual rack conversion.
Attached are a few pics of her sitting at a friends house. The rear is high because it's an incline and resting on the e-brake.
05-10-16, 11:27 PM
#32
LOF, yup, 4.10's and the Mazda R trans. I'm going to be looking into my suspension setup and rear diff next. I'm looking at a few avenues on both that I'm frankly surprised that no one has looked at before. But, more on that later regardless of whether they work or not.
Regardless, she has a safety inspection now along with two plates that lift the rear of the hood ~1.5". As I was having window regulator issues I also swapped to manual regulators. It's a rather simple swap, if tedious to realign and secure the glass. I didn't measure them but it also appears that it shaves off no weight. Don't forget the Dorman 76969 door handles! I'm having starter heatsoak issues (starter doesn't like to work when hot) but have a few ideas and avenues on how to address it.
I've seen a couple threads popup about bleeding the brakes so I thought I'd post this next tidbit. The short of the long is that you don't need any sort of 1 way valve or anything even remotely clever to do a one man brake bleed. I've personally found that speed bleeders tend to hurt more than they help and in general are prone to breaking/clogging and often let in small amounts of air via the threads.
A VERY simple way to address this is as follows:
1. Use clear hose on the brake bleed nipple.
2. Make a "large", "high" arc with the hose.
3. Crack the bleed nipple and pump the brakes as normal.
How this works has to do with fluid pressure and how it likes to flow. The arc makes the caliper the lowest point in the system and fluid will pool there first. Since the arc is higher than it the fluid can't just immediately drain out either which would otherwise leave the nipple exposed to air. Given that there is now fluid on outside the nipple only fluid can get sucked back. Also, if you really want a one way valve, buy some small plastic fish tank ones and splice them into the line (these are what's pictured: ) . However, again, they are NOT needed. I had some laying around and used them to illustrate.
A tip on the rear brakes; make absolutely sure you bleed BOTH nipples if you're putting on new calipers. For thoroughness you should technically bleed both regardless...
Regardless, she has a safety inspection now along with two plates that lift the rear of the hood ~1.5". As I was having window regulator issues I also swapped to manual regulators. It's a rather simple swap, if tedious to realign and secure the glass. I didn't measure them but it also appears that it shaves off no weight. Don't forget the Dorman 76969 door handles! I'm having starter heatsoak issues (starter doesn't like to work when hot) but have a few ideas and avenues on how to address it.
I've seen a couple threads popup about bleeding the brakes so I thought I'd post this next tidbit. The short of the long is that you don't need any sort of 1 way valve or anything even remotely clever to do a one man brake bleed. I've personally found that speed bleeders tend to hurt more than they help and in general are prone to breaking/clogging and often let in small amounts of air via the threads.
A VERY simple way to address this is as follows:
1. Use clear hose on the brake bleed nipple.
2. Make a "large", "high" arc with the hose.
3. Crack the bleed nipple and pump the brakes as normal.
How this works has to do with fluid pressure and how it likes to flow. The arc makes the caliper the lowest point in the system and fluid will pool there first. Since the arc is higher than it the fluid can't just immediately drain out either which would otherwise leave the nipple exposed to air. Given that there is now fluid on outside the nipple only fluid can get sucked back. Also, if you really want a one way valve, buy some small plastic fish tank ones and splice them into the line (these are what's pictured: ) . However, again, they are NOT needed. I had some laying around and used them to illustrate.
A tip on the rear brakes; make absolutely sure you bleed BOTH nipples if you're putting on new calipers. For thoroughness you should technically bleed both regardless...
05-23-16, 05:01 PM
#34
Thanks unek87, I'm glad you liked it and that I might see another in the future.
As to the car, very little was done that I could have. I did go on the cruise with the NoVA group which was quite enjoyable. I had only planned on meeting for the pre-cruise breakfast but figured, what the hell, and was along for the whole thing. Before going on the cruise I had found and fixed my hot start issue which turned out to be the 4ga wire leading to the starter was overheating (despite my routing it away from heat sources). I added a chunk of welding wire (0 ga?) I had laying around to the circuit and the engine turns over extremely easily now.
However, I have now had an intermittent issue with my fuel pump not working. I tracked that down to either the connector that goes into the bulkhead connector on the tank or the bulkhead connector itself. I am less than thrilled by this as I thought I had an adequate fix in place after I found it and ended up having to address it on the cruise... I've looked into a few solutions and like the racetronix one the best but their reputation the least. I'll probably end up getting a bit inventive.
For other "fixes" I need to put some damn mufflers on the car. Holy **** is she loud. On the return trip I think a Harley guy was offended and proceeded to blast by me. Him at full throttle and high (lol) rpm was barely louder than my car at cruise, in 5th, on the highway. So yeah... when you start thinking to yourself, "Hmm, I should have brought some ear-pro." you know it's time to quiet her down. I'll likely need more than one muffler to bring it down to a more reasonable level without sacrificing too much power which makes me a bit sad.
As to the car, very little was done that I could have. I did go on the cruise with the NoVA group which was quite enjoyable. I had only planned on meeting for the pre-cruise breakfast but figured, what the hell, and was along for the whole thing. Before going on the cruise I had found and fixed my hot start issue which turned out to be the 4ga wire leading to the starter was overheating (despite my routing it away from heat sources). I added a chunk of welding wire (0 ga?) I had laying around to the circuit and the engine turns over extremely easily now.
However, I have now had an intermittent issue with my fuel pump not working. I tracked that down to either the connector that goes into the bulkhead connector on the tank or the bulkhead connector itself. I am less than thrilled by this as I thought I had an adequate fix in place after I found it and ended up having to address it on the cruise... I've looked into a few solutions and like the racetronix one the best but their reputation the least. I'll probably end up getting a bit inventive.
For other "fixes" I need to put some damn mufflers on the car. Holy **** is she loud. On the return trip I think a Harley guy was offended and proceeded to blast by me. Him at full throttle and high (lol) rpm was barely louder than my car at cruise, in 5th, on the highway. So yeah... when you start thinking to yourself, "Hmm, I should have brought some ear-pro." you know it's time to quiet her down. I'll likely need more than one muffler to bring it down to a more reasonable level without sacrificing too much power which makes me a bit sad.
05-30-16, 01:13 AM
#35
Short update here although I haven't done anything per se.
I ordered a bunch of bushings for the read end. So I'll be dropping it in the coming month or so and dealing with that as well as swapping out my viscous for a helical swapped TII diff I picked up for a very good price. Once I swap the diffs I'll pull apart the viscous and see if the ring and pinion that I purchased because I think they'll fit actually do.
Otherwise, I picked up another weatherpack connector and some fuel safe wire (teflon coated). I decided to get inventive and am just going to get rid of the bulkhead connector and seal the wires as they pass through it and put the connector in place of the connector on the main body harness.
Does anyone happen to know offhand the extended and compressed length of the shocks front and rear?
I ordered a bunch of bushings for the read end. So I'll be dropping it in the coming month or so and dealing with that as well as swapping out my viscous for a helical swapped TII diff I picked up for a very good price. Once I swap the diffs I'll pull apart the viscous and see if the ring and pinion that I purchased because I think they'll fit actually do.
Otherwise, I picked up another weatherpack connector and some fuel safe wire (teflon coated). I decided to get inventive and am just going to get rid of the bulkhead connector and seal the wires as they pass through it and put the connector in place of the connector on the main body harness.
Does anyone happen to know offhand the extended and compressed length of the shocks front and rear?
04-13-17, 09:41 PM
#36
Almost a full year between updates... I'm almost tempted to wait. Oh well.
The items I bought for the TII rear end didn't go quite as well as I had hoped. I bought a ring and pinion from a Ford 8" (not 8.8) rear end. The pinion appears to be really, really similar to the usual RX short pinion (as I expected). The ring is almost identical to the TII 8" stock ring... except it's BG as opposed to SI. A few thou trimmed on its ID and a redrill of the TII mounting holes and the ring would fit at least.
I spent a great deal of time looking into custom coilovers only to scrap that idea. Instead I bought a set of Feal 441. It was them of a set of Fortune Autos. Both appear to have a good reputation in all areas. What clenched it for me was that the setup I ordered was slightly less expensive initially and if I ever want to upgrade them to 2-way it'll end up being ~$800 cheaper for what would be, in essence, the same thing. Once I get them in and installed I'll post my impression of them.
What I did manage to do is pictured below. I was having an issue with my cluster where the lights on it weren't working and the fault was somewhere in the board. Since I have a MS3 with MS3x I decided to make my own cluster. The short of the long is I 3d printed the holder for a 10.1" LCD, and connected a RPi3 which in turn is connected to my MS3 output. Oh yeah, I did the toyota mechanical to electric speedo conversion too. Enjoy the pics?
The items I bought for the TII rear end didn't go quite as well as I had hoped. I bought a ring and pinion from a Ford 8" (not 8.8) rear end. The pinion appears to be really, really similar to the usual RX short pinion (as I expected). The ring is almost identical to the TII 8" stock ring... except it's BG as opposed to SI. A few thou trimmed on its ID and a redrill of the TII mounting holes and the ring would fit at least.
I spent a great deal of time looking into custom coilovers only to scrap that idea. Instead I bought a set of Feal 441. It was them of a set of Fortune Autos. Both appear to have a good reputation in all areas. What clenched it for me was that the setup I ordered was slightly less expensive initially and if I ever want to upgrade them to 2-way it'll end up being ~$800 cheaper for what would be, in essence, the same thing. Once I get them in and installed I'll post my impression of them.
What I did manage to do is pictured below. I was having an issue with my cluster where the lights on it weren't working and the fault was somewhere in the board. Since I have a MS3 with MS3x I decided to make my own cluster. The short of the long is I 3d printed the holder for a 10.1" LCD, and connected a RPi3 which in turn is connected to my MS3 output. Oh yeah, I did the toyota mechanical to electric speedo conversion too. Enjoy the pics?
04-30-17, 03:17 AM
#37
In my quest for a better differential ratio for the lower revving LS1 (without going 8.8 or similar) I seem to have found something mazda truck guys have known for a long time. Particularly, Mazda only had 2 different differential styles around this time period. The M and P types. Unfortunately, Mazda didn't have a lot of different ratios. However, they did have a 3.727 in the P type (8" gear). Well, here is the website I found all this info on, read it yourself if you'd like: Mazda Differentials - Mazdatruckin.com
Long story short, I'll have a 3.727 rear end sooner than later. Now I just need to source another cheap TII driveshaft to alter, swap the ring gear to a torsen unit I have laying around, and figure out a pinion snubber since the B2600 3rd member doesn't have provisions for a front mount. I did have to wallow out the punkin a bit because of the diff I found have an ABS ring on it. If I could have found a non-ABS 3rd member it looked like it would have slipped right in.
Long story short, I'll have a 3.727 rear end sooner than later. Now I just need to source another cheap TII driveshaft to alter, swap the ring gear to a torsen unit I have laying around, and figure out a pinion snubber since the B2600 3rd member doesn't have provisions for a front mount. I did have to wallow out the punkin a bit because of the diff I found have an ABS ring on it. If I could have found a non-ABS 3rd member it looked like it would have slipped right in.
06-04-17, 08:28 PM
#38
For those that may be intersted, I ordered and received a set of Feal 441 coilovers. I ordered them in "road race" spec which means they're custom valved and sprung for my setup and application. They also appear to have arrived setup quite well too. I've only put ~40 miles on them thus far but am quite happy with them, how they drive, and their adjustability. In short, RX-7 feels a lot like my AP1 S2000 but with a slightly stiffer suspension and better compliance, predictability, controlability.
Not everything was perfect, although, I suspect it was partially another component faults. Particularly, the front brake line mounts were, with coating, ~0.020" too thick in width and the C slightly too closed (~0.015"). This wasn't a show stopper for me and was easily accomodated with minimal grinding. My strong suspicion is that the real problem wasn't the coilovers but my Goodrich braided lines as I had to do something similar with my OEM setup when I installed the Goodrich lines. Also, the fronts did some with a nice rubber insert that would have allowed me to not have to do this at all (it would have held the hardline from the caliper and kept it secure and from chaffing) but I prefer the OEM style spring retainers.
It would have also been nice if a clamp or ziptie of some sort was included to secure shock bellows to the shock body but I have those laying around. That they weren't secured did let me check them over fully and find the nice bump stops all included and in place. I wasn't in a hurry to receive them which was good as it took them a while to be shipped. If I had just ordered a regular set I would have gotten them in a week (it took ~5), but apparently a few components were out of stock and took a while to arrive in stock before they could be built. Either way, a good mod and should I want them to be 2-way adjustable it's an upgrade away.
Regardless, good components at a good price.
-------
On the differential front, things are coming along well, although, I get to wait on bearings now... hurray... It doesn't look like the 3rd member 3.727 gears will present any other issues though. I also found out that I didn't need to mod the diff case to put in the gears since I was moving the gear to a non-ABS differential. Oh well. I'll put up another post once it's in the car.
Not everything was perfect, although, I suspect it was partially another component faults. Particularly, the front brake line mounts were, with coating, ~0.020" too thick in width and the C slightly too closed (~0.015"). This wasn't a show stopper for me and was easily accomodated with minimal grinding. My strong suspicion is that the real problem wasn't the coilovers but my Goodrich braided lines as I had to do something similar with my OEM setup when I installed the Goodrich lines. Also, the fronts did some with a nice rubber insert that would have allowed me to not have to do this at all (it would have held the hardline from the caliper and kept it secure and from chaffing) but I prefer the OEM style spring retainers.
It would have also been nice if a clamp or ziptie of some sort was included to secure shock bellows to the shock body but I have those laying around. That they weren't secured did let me check them over fully and find the nice bump stops all included and in place. I wasn't in a hurry to receive them which was good as it took them a while to be shipped. If I had just ordered a regular set I would have gotten them in a week (it took ~5), but apparently a few components were out of stock and took a while to arrive in stock before they could be built. Either way, a good mod and should I want them to be 2-way adjustable it's an upgrade away.
Regardless, good components at a good price.
-------
On the differential front, things are coming along well, although, I get to wait on bearings now... hurray... It doesn't look like the 3rd member 3.727 gears will present any other issues though. I also found out that I didn't need to mod the diff case to put in the gears since I was moving the gear to a non-ABS differential. Oh well. I'll put up another post once it's in the car.
06-18-17, 06:34 PM
#39
Welp, looks like I got me sum 3.727 gears in my FC.
Yes, it was a bit of a pain in the ***. Yes, I saved a good chunk of money vs. going with a Ford 8.8 rear. No, it probably won't hold as much abuse as a Ford 8.8 rear end.
So here's how it went:
Looking around quite a bit it found a reference from the Mazda trucks guys that the differentials from Mazda were, fundamentally, only of two types based upon ring gear size. The Turbo II has an 8” ring gear which makes it a P type differential. The B2600 also predominately uses a P type differential.
The B2600i 2wd has a rear end that has a 3.727 ring and pinion. So... Cruising ebay for a while I found a 3rd member with that ring and pinion and bought it. The differential was an open type but I had a previous purchased FD torsen unit. I swapped the ring onto the torsen unit, replaced the bearings (more on this later) and reinstalled it in the 3rd member.
As can be seen in the picture, the 3rd member was from an ABS unit and it didn't come with the ABS sensor. As such, I took a 3/4” bolt, cut it down, and along with an o-ring, some sealant, and a welder, made a working plug for ~$5 as opposed to $50. Of note is that the ABS exciter ring is on the differential itself and is NOT a spacer. As such, so long as you're putting the ring gear on a non-ABS differential then you do NOT need to modify the differential housing.
Once all of that was done, the 3rd member drops right into the differential housing and bolts to it. You'll need to use whatever stub shafts fit both your housing AND housing seals. So... I currently have an FC diff. housing with a B2600 3rd member containing an FD torsen unit. Now... onto the not fun part.
As can be seen in my pictures, I had to cut up a portion of my rear subframe. No, I'm not worried about any appreciable weakening of the subframe because of this (automotive FOS >= 2.5). It was incredibly annoying to do with since I didn't have any templates and had to jack up, check fit, then drop and cut some material from the subframe a dozen or so times.
Regardless, it's done and everything clears and it drives. I still have to make some sort of pinion snubber as with enough torque (1st and 2nd gear) and more than ~1/2 throttle the 3rd member moves enough that a part of it will smack the subframe and make a loud clunk. Also, the B2600 3rd member is ~6” shorter than the FC TII 3rd Member which means anyone else doing this will need to lengthen their driveshaft. Speaking of driveshafts, apparently I didn't shorten the one I purchased for this well enough so now I get to buy a professionally made driveshaft as it has a high speed vibration... Fffffuuuuuuuuu...
I did find a source for rear end bearings, although, I did not end up using them (123bearing). They had incredibly good prices on the (IIRC) R45Z-1 carrier bearings. Unfortunately, they're drop shipped from overseas... Looking around, doing parts interchanges, etc., etc. I found a non-Mazda carrier bearing part number: KC11445Y .
I found something else of interest. It APPEARS (I don't know 100%) that the older Toyota 8” rear gear and pinion will fit in the B2600 3rd member. Actually, it appears the Toyota 8” 3rd member will fit in the TII differential housing. If this is the case it gives a rear gear selection from 3.00 – 5.xx. However, while the pinion bearings between the Mazda and Toyota are the same, the Carrier bearings are ever so slightly different. So, anyone experimenting with this will need to get the carrier bearings for whichever 3rd member they purchase. Oh yeah, the Toyota 8” uses a 27 or 29 spline pinion. The Mazda is 28 spline. Also, the Toyota uses a smaller flange bolt configuration so you'll have to make an adapter. But hey, them gear choices (maybe, I haven't tested it, just compared a LOT of pictures and bearings).
So yes, this was a pain in the ***, and like most of the stuff I've done, not for the faint of heart. Hopefully this helps someone out but keep in mind, while this will save you money, it will take more effort than just buying a bunch of parts to slap together. You also have to be comfortable cutting up a subframe : D
Yes, it was a bit of a pain in the ***. Yes, I saved a good chunk of money vs. going with a Ford 8.8 rear. No, it probably won't hold as much abuse as a Ford 8.8 rear end.
So here's how it went:
Looking around quite a bit it found a reference from the Mazda trucks guys that the differentials from Mazda were, fundamentally, only of two types based upon ring gear size. The Turbo II has an 8” ring gear which makes it a P type differential. The B2600 also predominately uses a P type differential.
The B2600i 2wd has a rear end that has a 3.727 ring and pinion. So... Cruising ebay for a while I found a 3rd member with that ring and pinion and bought it. The differential was an open type but I had a previous purchased FD torsen unit. I swapped the ring onto the torsen unit, replaced the bearings (more on this later) and reinstalled it in the 3rd member.
As can be seen in the picture, the 3rd member was from an ABS unit and it didn't come with the ABS sensor. As such, I took a 3/4” bolt, cut it down, and along with an o-ring, some sealant, and a welder, made a working plug for ~$5 as opposed to $50. Of note is that the ABS exciter ring is on the differential itself and is NOT a spacer. As such, so long as you're putting the ring gear on a non-ABS differential then you do NOT need to modify the differential housing.
Once all of that was done, the 3rd member drops right into the differential housing and bolts to it. You'll need to use whatever stub shafts fit both your housing AND housing seals. So... I currently have an FC diff. housing with a B2600 3rd member containing an FD torsen unit. Now... onto the not fun part.
As can be seen in my pictures, I had to cut up a portion of my rear subframe. No, I'm not worried about any appreciable weakening of the subframe because of this (automotive FOS >= 2.5). It was incredibly annoying to do with since I didn't have any templates and had to jack up, check fit, then drop and cut some material from the subframe a dozen or so times.
Regardless, it's done and everything clears and it drives. I still have to make some sort of pinion snubber as with enough torque (1st and 2nd gear) and more than ~1/2 throttle the 3rd member moves enough that a part of it will smack the subframe and make a loud clunk. Also, the B2600 3rd member is ~6” shorter than the FC TII 3rd Member which means anyone else doing this will need to lengthen their driveshaft. Speaking of driveshafts, apparently I didn't shorten the one I purchased for this well enough so now I get to buy a professionally made driveshaft as it has a high speed vibration... Fffffuuuuuuuuu...
I did find a source for rear end bearings, although, I did not end up using them (123bearing). They had incredibly good prices on the (IIRC) R45Z-1 carrier bearings. Unfortunately, they're drop shipped from overseas... Looking around, doing parts interchanges, etc., etc. I found a non-Mazda carrier bearing part number: KC11445Y .
I found something else of interest. It APPEARS (I don't know 100%) that the older Toyota 8” rear gear and pinion will fit in the B2600 3rd member. Actually, it appears the Toyota 8” 3rd member will fit in the TII differential housing. If this is the case it gives a rear gear selection from 3.00 – 5.xx. However, while the pinion bearings between the Mazda and Toyota are the same, the Carrier bearings are ever so slightly different. So, anyone experimenting with this will need to get the carrier bearings for whichever 3rd member they purchase. Oh yeah, the Toyota 8” uses a 27 or 29 spline pinion. The Mazda is 28 spline. Also, the Toyota uses a smaller flange bolt configuration so you'll have to make an adapter. But hey, them gear choices (maybe, I haven't tested it, just compared a LOT of pictures and bearings).
So yes, this was a pain in the ***, and like most of the stuff I've done, not for the faint of heart. Hopefully this helps someone out but keep in mind, while this will save you money, it will take more effort than just buying a bunch of parts to slap together. You also have to be comfortable cutting up a subframe : D
06-19-17, 10:34 AM
#41
Sucks about the driveshaft 
https://www.rx7club.com/2nd-generati...shaft-1081644/
I have a spare t2 transmission yoke w/ a 7260 to 1310 conversion U joint on it if you're interested.
https://www.rx7club.com/2nd-generati...shaft-1081644/
I have a spare t2 transmission yoke w/ a 7260 to 1310 conversion U joint on it if you're interested.
06-19-17, 11:24 PM
#42
LOF, Heh, I guess it is different, although, the point is being cheap! I've been sorely tempted to buy a toyota 8" 3rd member but it and some gears will be noticeable to my wallet...
eage8, I kind of expected it to be honest... I recall reading on a locost forum that driveshafts under 24" center-to-center tend to not need balancing whereas those over it do. With the 4.10 my modded driveshaft was ~19.5" CTC whereas this one is ~25.5" CTC. That's some good info you put together in that link... I'll have to explore that avenue in detail.
eage8, I kind of expected it to be honest... I recall reading on a locost forum that driveshafts under 24" center-to-center tend to not need balancing whereas those over it do. With the 4.10 my modded driveshaft was ~19.5" CTC whereas this one is ~25.5" CTC. That's some good info you put together in that link... I'll have to explore that avenue in detail.
06-22-17, 12:55 PM
#43
Senior Member
This is great info, I think a buddy of mine might have a Toyota axle kicking around, I'm now going to bug him to let me measure it. I'm sure a carrier bearing in the correct size exists.
Is the diff just on the rear "wing" mounts and nothing attached to the subframe where the front mount was?
Is the diff just on the rear "wing" mounts and nothing attached to the subframe where the front mount was?
Last edited by teeson; 06-22-17 at 09:55 PM.
06-24-17, 11:05 PM
#44
teeson, I look forward to hearing how it goes. As to the carrier bearings. The Mazda and Toyota ones are different, although, IIRC the difference is that the Toyota bearing is ~0.0005" larger OD. I'm out of town or I'd verify it. Either way, the Toyota bearings aren't terribly hard to get.
I currently don't have any extra support for the diff. beyond the wings. That being said I plan on making an upper and lower snubber for support and movement control as I suspect where the wings connect is flexing. I also plan on cutting out more of the subframe and boxing the cut out section.
I currently don't have any extra support for the diff. beyond the wings. That being said I plan on making an upper and lower snubber for support and movement control as I suspect where the wings connect is flexing. I also plan on cutting out more of the subframe and boxing the cut out section.
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