renns

I have a 1979 RX-7 (SA) that is now running a boosted 6-port engine, and am collecting parts for the swap over to TII transmission. I still need a starter, and custom driveshaft, but the rest is at hand now. I've read through the "TII in an FB" threads, any haven't seen any pics of the actual transmission modifications. Here's what I've found so far.

With the SA and TII (JSpec) transmissions sitting side-by-side, I took some measurements:



From the bellhousing back, the stock SA shifter pivot is about 27-3/8" back. The TII shift pivot is about 32-3/4" back, for a difference of 5-3/8". There appears to be enough free length on the shifter rod and tube to shorten by this amount, but the housing would required some serious modifications to move forward by that amount. Below is a pic showing the mods needed to the shifter housing. The housing would be cut as shown by the vertical line, and the housing relocated to the left 5-3/8" to use the original two mounting holes shown on the left. The remaining two mounting holes could support a sheet metal bracket fabricated to hole the end of the shifter housing.



There doesn't appear to be any possibility of swapping tailshaft housings, as the bolt pattern is different between the TII and SA. For reference, the TII tailshaft housing bolt pattern differs from the S5 na tranny I have as well.

Also, the alignment pin for the TII shifter is mounted on the front side of the housing, while on the SA it is on the rear. Cutting another groove in the opposite side of the spherical ball would take care of that issue.

Any thoughts from those that have been through this before?

gonzz

What i did was just install the TII eng and trans. Cut further back to mount the TII shifter and then welded some metal in.. I like the shifter to the rear more than the stock location..
Pm me and wil send you some pics..

Dan_s_young

iTrader: (1)

If its not too much trouble I would like to see some pictures of that as well gonzz, thanks!

(if you want to send them by email my email address is: Dan_s_young@msn.com)

gonzz

E-mail sent

Jeff20B

iTrader: (13)

This might be of help. http://www.geocities.com/mg12a/mg12a/intro.html

renns

Thanks Jeff. If the 4" was enough, simply shuffling the assembly forward like you did would be great. I doubt that'll look right with the stock console, so I'll need to do some more elaborate fabrication.

For others reading this thread, here's another excellent site showing pics of shifter linkage modifications. The are reworking FB to SA configuration, but the inner workings are likely similar.

http://www.geocities.com/izzmus/trans/trans.html

craigw1

what i did was to replace the tailpiece of the s5 tii box with the 12A one. I then removed the shaft and cut the end off...about 1.5cm. I then also drilled a new alignment hole. I tapped this hole as well. the screw goes into there and into the metal block which is a cup for the ball joint of the gear lever.

this whole process takes a while. for some people I've seen on here it works first time. My first time did not work properly because when i then assembled the box (outside the car of course) I couldn't engage 2nd/4th/reverse properly...so i had obviously cut it wrong as it was hitting against the rear of the housing. moral of the story...you have to assemble and test outside the car first. I cannot emphasise this point enough. In the end i wasted 1 rod and had to do it all over again. but on my second attempt it worked perfect....gear selection all fine.

one more trick to fitting though. you have to fabricate a gearbox mount as the original 12a mount will be too big and knock the box against the body. This mount is then between the gearbox and the original cross member. I used two pieces of metal with a hard rubber sandwiched in between.

after that, the stick should line up perfectly. then get your custom driveshaft fitted, and top up with oil. remember, there is one hole to fill the oil, and another hole to check the level, not like with the 12a when it was just the same hole.

also, watch out for the conections. the box has about 3 different switches...like a neutral switch, etc. u just need to hook up the reverse only

here is a pick of my custom tranny mount

renns

Thanks for the info. It sounds like you've gone a different route to the same end. Could you explain further the tailpiece mods? The TII box I've got appears to have a different extension housing (tailstock) bolt pattern than either of the two non turbo boxes I have in my shop. I haven't actually disassembled to check, but they sure don't look identical. Also, since the extension housing surrounds the output shaft, how does the larger TII output shaft fit properly in the 12A housing? Many thanks.

craigw1

sorry for the confusion.

in the pic you can see the extention housing of the 12a box fitted to the tii box. The original tii one is slightly longer

you then have to remove the selector as well, and cut a piece off from the end and redrill a new hole. Make damn sure you get the location angle exactly in line with the original hole ie. first drill another hole then cut the end piece off.

in the second pic you can see the 12a tailpiece on the tii box with the shortened selector tube (piece has already been cut off and redrilled)

in the third pic you can see the original tii tailpiece back on the tii box with the shortened selector piece. here you can see how much has been cut off.

you also have to cut a piece of the selector shaft tube off and reseal.

hope this is clearer

good luck. Like I said, mine never worked first time and i again had to cut off a piece from another selector. Also, its quite tricky to put the selector back and juggle the tailpiece in...it took me a while....everytime i then tried to measure up the shaft, it would come out of its position...then i would have to loosen the whole thing up again. this whole thing took me the best part of a saturday to complete. But I tell you, I am now an expert on this conversion.

renns

OK, thanks for the details. It looks like you are swapping over what the FSM calls the "Change Control Case". That works for swapping in to FB series cars, but the earlier SA tranny has the change control case built in to the extension housing, so it can't be swapped separately. I suppose I could find an FB change control case, and then modify the tunnel of the car to suit the FB shifter location.

On another issue, how did you sort out your driveshaft? I took the TII yoke and SA driveshaft to the local driveshaft shop, but they had nothing for me. From discussions with that guy, the only option is to swap out the companion flange on the rear axle to a larger unit (likely custom machined part), which would then allow the same size universals front and rear.

Thanks again for the info and pics.

Jeff20B

iTrader: (13)

I'm telling you man, it's not necessary. It turns out I did shoot a few pics of my shifter housing mod after all. This tranny fits fine in an RX-4 which has the exact same shifter location as an SA.

Pulling the alignment dowels out of the tail housing. Just ignore the other stuff in the picture. Not pictured is the removal of one of the threaded attatchment points at the rear.


The rod after drilling and tapping (unnecessary on T2 rod)


A closeup before cutting.


The completed mod. The shaved rear attatchment point is behind the shifter housing.


This tranny is an '81-'83 with the big gears (as pointed out on peejay's website). If it had been the other type with the smaller gears, I wouldn't have bothered modding it.


I also did a short shifter (not pictured) and used the RX-4 shift lever due to the shift boot and the driving position of the car. The SA is similar but shorter and you could probably get away with the FB/T2 shorter lever. Or you could purchase a short shifter kit and install the SA lever above the big slotted ball. I cut the small ball off the bottom of the RX-4 shifter and welded on the FB ball. Works great in the RX-4 and the throws are 1/2" shorter than stock.

renns

Thanks for the extra pics Jeff. I am clear on the mods you did, and I'm sure it worked great for you. I have my doubts in my SA, though, as the dimensions clearly show another 1-3/8" movement is required beyond what your mods provide in order to match the original shifter location perfectly. If 'close enough' was good enough, then all those FB guys would use the TII tranny as-is, rather than swapping the FB change control case and cutting the shifter rod down that 3 cm (less than 1-1/4").

Blake

What I did on my peripheral port 13B race car was to modify a 2nd gen (86-91) NA companion flange (slightly larger flange) to fit a 1st gen pumpkin. It took a little machining to make a spacer ring and then find an off-the-shelf seal, but it was not that big of a deal. The bolt holes had to be slotted, but the driveshaft and companion flanges positively center on a male/female ring, so you can't screw it up. The TII driveshaft was lengthened for $99 at a driveline shop. I prefer using a complete TII driveshaft, since it has such large U-joints. If you didn't want to swap companion flanges, the common approach is to make a custom driveshaft, which sould be less than $300. If your driveline shop says they can't do it, go find another driveline shop.

Jeff20B

iTrader: (13)

I see. I wonder if it would be possible to swap in a 1st gen shift selector housing and rod instead. Have any 1st gen owners done this?

The 1st gen selector housing in this new posiition lines up perfectly in the RX-4 hole. The RX-4 rubber cover fits great.

craigw1

Re the drivesgaft, this is what I did :

after fitting motor/gearbox I towed the car to local driveshaft place. Took my old 12A driveshaft with. They then custom made a new shaft with a yoke to fit the tii and the flange from my 12A shaft. was obviously balanced as well. I dropped the car off the morning and towed back the evening. better to take the car there and get the guys to fit themself rather than giving them measurements. also, I asked them to make the new shaft the same diameter as the original tii shaft (per heynes manual specification). the tii shaft is slightly wider in diameter than the 12A shaft.

renns

Ah, now you are cooking with gas! That's probably the cleanest solution to avoid welding a new ear on. I just recently sent my only spare 81-85 tranny off to a GSL-SE owner in need. I'll have to see if I can get the remains of his old tranny back to scavenge that "change control case" for trimming and mounting to the TII tranny. Thanks for that idea!

Blake, just to clarify here, the 2nd gen companion flange ID is a direct fit on the splines of the FB drive pinion? Only OD was modified to fit inside the housing properly?

I'm with you on this one. There are two shops in town, and I went to the larger one. They showed no interest in figuring out a solution. As soon as I said 'Mazda', I could tell by the guy's expression I was going to leave empty handed.

Blake

Yes, the splines are the same. As far as the OD...my memory is not reliable; this was about five years ago. We did use a thin (ID/OD) custom spacer, but I think it may have had more to do with the bearing we ended up using (some off-the-shelf Federal Mogul part we had lying around)...I dunno. A lot of water under that bridge. Sorry I can't be more helpful.

Jeff20B

iTrader: (13)

I found myself wracking my brain today in my spare moments to try to come up with an FB "change control case" for when I do a T2 tranny myself. I know of one FB tranny that's noisy with a lot of miles, but it still works. Maybe when it breaks I can get it from the guy as payment for helping him swap in another tranny. Hmm...

Felgar

Craigw1, did you do anything to correct the speedo when you did the swap? On the NA FC->FB conversions the tailhousing gets switched which takes care of the problem. But the worm gear from your FB output shaft wouldn't fit into the TII tranny, right?

Jeff20B... Too bad you don't live closer. I'd gladly trade a worn transmission from a '84 GS for help installing and setting up an aftermarket ECU.

craigw1

nope. did nothing re the speedo cable. just screwed it in. I have a feeling it over reads a little. How do you suggest I correct ?

Jeff20B

iTrader: (13)

Indeed.

Felgar

I have no idea craigw1...

In the end, the worm gear and speedo gear are essentially just a multiplier to account for your tire size and rear-end ratio (the only thing between the output shaft and your ground speed)... Since the proper worm gear won't fit onto the TII shaft (and also you probably don't want to drop the tranny and split the tailhousing just to change it) maybe there's an after-market gear you could get that would work with the current worm gear but adjust the speed properly... Like I said though, I have no idea.

renns

I'll look at the speedo gear issue when I get my TII tranny apart. If the gear OD is the same, the it's possible the gear could be bored to match the larger TII shaft.

As for fitting a TII tranny into an SA while maintaining stock shifter location, there's still a couple more issues to address:

1.) Alignment pin groove in the FB and later shifters is at the front, while the groove in the SA shifter is at the back.

2.) The bottom of the SA shifter is significantly longer than the FB and later units. See attached pic. This means that even if the shifter were modified to address item 1.), the SA shifter still wouldn't work in later boxes.



If desperate, a custom SA shifter could be fabricated by using the bottom portion of an FB or later shifter, with the addition of the offset upper portion. This would address both of the above issues.

For my install, I think the best option will be to modify the transmission tunnel, moving the shifter hole back to FB position. I have a mint FB console that matches the car, so that would finish up the interior nicely. It's another step away from being an authentic 'SA', but it's already such a hybrid that those issues are irrelevant.

Also, while researching this issue, I disassembled a spare S5 n/a tranny I had on the shelf. It appears identical to the S4 units except it has a dynamic damper mounted to the output shaft. For those interested in converting an S5 n/a back to SA configuration, this damper would need to be removed to fit the SA extension housing.

Felgar

Are the shift forks exactly the same between the S4 and S5 NA? I thought I read that there was a slightly different shift action in the S5's (the S5's not having as much distance between 1st and 3rd).

What exactly is a dynamic damper? And would it interfere with the typical s2/s3 FB tail housing?

renns

I can't say for certain, as I don't have an S4 box open at the moment. I can say that the three shift rods that extend into the box are in the same position in both the SA and S5 trannies, and likely identical on other models as well. The actuating rod from the shifter is in a different position between those two boxes. The shift fingers are definitely in a different orientation between SA and S5 to accomodate the different actuating rod position. Below is a pic of the S5 shift finger positions for comparison if you have an S4 box open.



The dynamic damper is a small flywheel-type device, rubber isolated from the hub which is locked to the output shaft. It spins with the output shaft inside the extension housing. It definitely interferes with the SA housing, but I can't speak to the FB housing. The damper is easy enough to remove if needed. That huge nut tightens on to the body of the damper, pushing two tapered sleeves between the damper and shaft to lock it in place. A couple whacks with a hammer and punch, and the large nut spins off easily. Then remove the retaining ring below the damper, and give the damper a tap to slide it off those tapered sleeves. All components slide up off the end of the output shaft, leaving you with a box that appears ready to accept an SA or FB extension housing.