Transmission re-gearing.
08-01-01, 10:38 PM
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Transmission re-gearing.
If one upgrades to 4.44 gears for autocross, you drop your top crusing speed. However, after thinking about it for a while, I devised a way to combat this.
You're in 2nd or 3rd gear mostly during an autocross, so leave those gears the same, but modify 4th and 5th for highway speeds.
Calculate entire drivetrain ratio by multiplying tranny ratio by rear gear ratio. Find the required ratio you need in the tranny by dividing the entire ratios.
Example. Stock rear ratio is 3.9 and 4th gear is 1... This makes the entire drive train ratio 3.9... Changing the rear axle ratio to 4.44 changes the total ratio, so to compensate, 4th gear would have to be lowered to .878 or so. Similar calculations can be made for the 5th gear dependant on whether it is a 13B or 12A tranny.
To get into 4th, you'd have to drive a little higher in the RPMS while in third, but that shouldnt be too big of a problem.
My question is: Is gear swapping possible? Where can I find different ratio gears?
You're in 2nd or 3rd gear mostly during an autocross, so leave those gears the same, but modify 4th and 5th for highway speeds.
Calculate entire drivetrain ratio by multiplying tranny ratio by rear gear ratio. Find the required ratio you need in the tranny by dividing the entire ratios.
Example. Stock rear ratio is 3.9 and 4th gear is 1... This makes the entire drive train ratio 3.9... Changing the rear axle ratio to 4.44 changes the total ratio, so to compensate, 4th gear would have to be lowered to .878 or so. Similar calculations can be made for the 5th gear dependant on whether it is a 13B or 12A tranny.
To get into 4th, you'd have to drive a little higher in the RPMS while in third, but that shouldnt be too big of a problem.
My question is: Is gear swapping possible? Where can I find different ratio gears?
08-02-01, 10:52 AM
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As far as finding a 4.44 ring and pinion, you could try finding an 87 or 88 4wd B2000 pickup (mine came out of the front member).
I'm still somewhat conflicted on what I think about using the 4.44 though (my car is a 79 and I am using the 79 tranny w/stock gearing there).
Here is my problem with it: with the 4.44 I seem to go through 1st and 2nd gear very quickly (this makes sense of course). However, it also seems that when I shift out of second (which admittedly is a bit earlier -- around 6000-6500 rpm because of how fast the revs climb now), I am only moving around 35-40 mph. This creates the odd situation of my dropping the hammer in, say, second gear, but by the time I shift into 3rd, I'm really only beginning to catch up w/traffic in front of me that is moving at around the legal speed limit (I should also say here that I don't condone street racing, but I also know that most of us -- including me
-- engage in it from time to time; I guess it's a testosterone thing.
This, then, creates the feeling that the car is slower than it should be...basically a "damn ... I'm nailing it and through w/second gear already and am just now doing normal traffic speeds. Perhpas once I get more used to it and can shift a bit closer to redline, this feeling won't be so dramatic. It may also reduce your 1/4 mile time (if drag racing is your thing -- and this is simply my oppinion here) because you are having to shift more often while other cars are accelerating away from you. Of course, 3rd and 4th is typically where I would think things would start to even out and the gearing advantage would be most usable -- but then again, from what I understand, gearing advantage tends to be less dramatic in the higher gears than in the lower gears due to (I assume) principles of torque multiplication.
At any rate, I guess what I am trying to say is that I'm not certain that my switching to a 4.44 final drive was such a great idea in retrospect. It seems like the only difference is that I am shifting more often and at a lower speed rather than gaining any significant acceleration advantage. Then again, it's difficult to take accurate before and after feelings when you can't switch off to how the car was before the swap and how it is after the swap.
Just my ramblings I guess...does anyone else have any input in regard to this phenomenon?
I'm still somewhat conflicted on what I think about using the 4.44 though (my car is a 79 and I am using the 79 tranny w/stock gearing there).
Here is my problem with it: with the 4.44 I seem to go through 1st and 2nd gear very quickly (this makes sense of course). However, it also seems that when I shift out of second (which admittedly is a bit earlier -- around 6000-6500 rpm because of how fast the revs climb now), I am only moving around 35-40 mph. This creates the odd situation of my dropping the hammer in, say, second gear, but by the time I shift into 3rd, I'm really only beginning to catch up w/traffic in front of me that is moving at around the legal speed limit (I should also say here that I don't condone street racing, but I also know that most of us -- including me
-- engage in it from time to time; I guess it's a testosterone thing. This, then, creates the feeling that the car is slower than it should be...basically a "damn ... I'm nailing it and through w/second gear already and am just now doing normal traffic speeds. Perhpas once I get more used to it and can shift a bit closer to redline, this feeling won't be so dramatic. It may also reduce your 1/4 mile time (if drag racing is your thing -- and this is simply my oppinion here) because you are having to shift more often while other cars are accelerating away from you. Of course, 3rd and 4th is typically where I would think things would start to even out and the gearing advantage would be most usable -- but then again, from what I understand, gearing advantage tends to be less dramatic in the higher gears than in the lower gears due to (I assume) principles of torque multiplication.
At any rate, I guess what I am trying to say is that I'm not certain that my switching to a 4.44 final drive was such a great idea in retrospect. It seems like the only difference is that I am shifting more often and at a lower speed rather than gaining any significant acceleration advantage. Then again, it's difficult to take accurate before and after feelings when you can't switch off to how the car was before the swap and how it is after the swap.
Just my ramblings I guess...does anyone else have any input in regard to this phenomenon?
08-02-01, 11:28 AM
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Pele,
I would assume gears are interchangable, but I don't know that for sure.
Ken is right that a 4.44 will make you shift more often than a 3.90. This will either be good or bad depending on what you're doing, what kind of gear box you have, and how good you are at shifting. In road racing, the more shifts I make during a lap, the better, because that means I'm always in the narrow power band our engines produce. What I shoot for when deciding which of my rear ends to use at a given track (I have a 4.44, 4.88, and a 5.13) is I want to be out of RPM in top gear just prior to lifting at the end of the fastest straight away.
For autocrossing, I would look to find a gear that would allow me to be in 2nd gear for the vast majority of the run. That way I could shift as little as possible (particularly beneficial for a newbie). Syncro gear boxes take time to shift, and critical RPMs are lost during that time.
Chuck
I would assume gears are interchangable, but I don't know that for sure.
Ken is right that a 4.44 will make you shift more often than a 3.90. This will either be good or bad depending on what you're doing, what kind of gear box you have, and how good you are at shifting. In road racing, the more shifts I make during a lap, the better, because that means I'm always in the narrow power band our engines produce. What I shoot for when deciding which of my rear ends to use at a given track (I have a 4.44, 4.88, and a 5.13) is I want to be out of RPM in top gear just prior to lifting at the end of the fastest straight away.
For autocrossing, I would look to find a gear that would allow me to be in 2nd gear for the vast majority of the run. That way I could shift as little as possible (particularly beneficial for a newbie). Syncro gear boxes take time to shift, and critical RPMs are lost during that time.
Chuck
08-02-01, 02:09 PM
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Originally posted by Chuck Clark
Pele,
I would assume gears are interchangable, but I don't know that for sure.
Ken is right that a 4.44 will make you shift more often than a 3.90. This will either be good or bad depending on what you're doing, what kind of gear box you have, and how good you are at shifting. In road racing, the more shifts I make during a lap, the better, because that means I'm always in the narrow power band our engines produce. What I shoot for when deciding which of my rear ends to use at a given track (I have a 4.44, 4.88, and a 5.13) is I want to be out of RPM in top gear just prior to lifting at the end of the fastest straight away.
For autocrossing, I would look to find a gear that would allow me to be in 2nd gear for the vast majority of the run. That way I could shift as little as possible (particularly beneficial for a newbie). Syncro gear boxes take time to shift, and critical RPMs are lost during that time.
Chuck
Pele,
I would assume gears are interchangable, but I don't know that for sure.
Ken is right that a 4.44 will make you shift more often than a 3.90. This will either be good or bad depending on what you're doing, what kind of gear box you have, and how good you are at shifting. In road racing, the more shifts I make during a lap, the better, because that means I'm always in the narrow power band our engines produce. What I shoot for when deciding which of my rear ends to use at a given track (I have a 4.44, 4.88, and a 5.13) is I want to be out of RPM in top gear just prior to lifting at the end of the fastest straight away.
For autocrossing, I would look to find a gear that would allow me to be in 2nd gear for the vast majority of the run. That way I could shift as little as possible (particularly beneficial for a newbie). Syncro gear boxes take time to shift, and critical RPMs are lost during that time.
Chuck
What other types of gear boxes are available besides synchro?
Last edited by Pele; 08-02-01 at 02:12 PM.
08-02-01, 07:22 PM
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Pele,
Most racing gear boxes are either dog ring or sequential. Both of those types will allow you to shift with out the use of the clutch (this will save you precious tenths of seconds on shifts). The problem is, most dog ring boxes cost $5,000-$8,000, and sequential boxes go for anywhere from $15,000 to $45,000.
Not to mention, using one of those trannies would move you up into the Prepared Category in Solo2.
I have a dog ring box in my car. I don't use the clutch on upshifts, but I do on downshifts because it's easier on the tranny and diff. My gear ratios are as follows:
1st 2.07:1
2nd 1.61:1
3rd 1.34:1
4th 1.16:1
5th 1:1
Obviously, I don't lose much RPM on shifts with those tight ratios, but that gear box costs $5,300.
Chuck
Most racing gear boxes are either dog ring or sequential. Both of those types will allow you to shift with out the use of the clutch (this will save you precious tenths of seconds on shifts). The problem is, most dog ring boxes cost $5,000-$8,000, and sequential boxes go for anywhere from $15,000 to $45,000.
Not to mention, using one of those trannies would move you up into the Prepared Category in Solo2.
I have a dog ring box in my car. I don't use the clutch on upshifts, but I do on downshifts because it's easier on the tranny and diff. My gear ratios are as follows:
1st 2.07:1
2nd 1.61:1
3rd 1.34:1
4th 1.16:1
5th 1:1
Obviously, I don't lose much RPM on shifts with those tight ratios, but that gear box costs $5,300.
Chuck
08-02-01, 08:42 PM
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The only way that i know of to get different gear ratio's in our tranny's is to use old 626 gears. Basically you can swap the guts from a 626 gear box into your tranny. The ratios are closer than our stock gears. I know of a couple of people who have done this with good results. You have to use the early eighties RWD 626's gear box. I can get more detailed info if anyone is interested.
Mike
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08-02-01, 09:47 PM
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My backup tranny is a 626 conversion. It's a nice upgrade over stock RX-7 ratios, and it's relatively easy to do. The 626 gears will bolt right into an RX-7 case. You have to machine about 1/4" off of the splines on the input shaft, but other than that, it's a pretty straight forward swap.
The great thing about those 626 boxes, is they are generally in good condition because the motors in those cars had no HP, and they usually ended up in the junk yard before 100,000 miles. The bad thing is they only made rear wheel drive 626s for a couple of years, so they can be hard to find.
The great thing about those 626 boxes, is they are generally in good condition because the motors in those cars had no HP, and they usually ended up in the junk yard before 100,000 miles. The bad thing is they only made rear wheel drive 626s for a couple of years, so they can be hard to find.
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08-03-01, 05:17 PM
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Combine info from two threads.
Okay, so combine the info from the tranny rebuild thread and this one. Someone said once you get the bearings pressed off the shaft, the gears and synchros just slip right off. Can you slip different individual gears and synchros back on? I forget who gave me it, but it's a neat little spread sheet in MS Excel format that shows Mazda gearbox ratios. Too bad I can't attach it...
03-05-06, 09:41 AM
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HA!! Why spend $5300 on a racing gearbox when you could just tear into a stock transmission and file every other tooth off on every syncronizer. It will result in the same thing and cost much less. Old hot rodding trick
03-05-06, 02:42 PM
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Ahhh - good to hear from ripoff Clark. Your advice is free, so I guess it's worth the money. Steal anyone else's money for junk engines lately? How's your concience scumbag?
03-05-06, 04:35 PM
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Originally Posted by Pele
If one upgrades to 4.44 gears for autocross, you drop your top crusing speed.
I have no problem cruising at 90mph with 4.78's. I generally keep it down to 75ish, though.
Note that under heavier loads, 5th gear in my trans shakes the car like a wet dog, so I'm running those speeds in FOURTH gear
edit: Just realized, ancient thread, but still. I'm still getting 25+mpg at a 5000rpm cruise...
06-22-08, 12:26 AM
#13
I'll do the honours to retrieving a thread from the dead again. Curious if anyone know of any other cars now that we can maybe retrieve the gearing from besides the 626. Personally I don't like the huge jump that we have inbetween 2nd and 3rd gear. I would like to have something that is a little closer in ratios.
06-22-08, 10:46 AM
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Talk about a double revival..... 1st it was 4.5 years, then again after another 2.25 years.
Anyways, to answer dj55b's question. The Miata trans internals will interchange with a FB/FC trans, but the input shaft needs minor milling. The milling requires removing about 3/8" from the splines.
Miata's have better ratios inside the trans. A Miata with a 4.10 rear gear can actually acheive a higher speed in 2nd than a stock FB or FC in 2nd, at the same RPM.
FWIW, the Miata ring and pinion is also a direct fit for the FB rearend. In fact, the auto trans Miata uses the same 3.90 gears, while 5spd Miata's have either a 4.10 or 4.30.
Anyways, to answer dj55b's question. The Miata trans internals will interchange with a FB/FC trans, but the input shaft needs minor milling. The milling requires removing about 3/8" from the splines.
Miata's have better ratios inside the trans. A Miata with a 4.10 rear gear can actually acheive a higher speed in 2nd than a stock FB or FC in 2nd, at the same RPM.
FWIW, the Miata ring and pinion is also a direct fit for the FB rearend. In fact, the auto trans Miata uses the same 3.90 gears, while 5spd Miata's have either a 4.10 or 4.30.
06-22-08, 03:38 PM
#15
^^ I concur. My 73 RX-3 is equipped with a miata 5-speed tranny modified using FB bellhousing and tailshaft along with shortened input shaft. It may not be as strong as TII trannies but it weight less.
If you give me a choice between a 626 RWD and Miata, I will take the miata since it is newer.
If you give me a choice between a 626 RWD and Miata, I will take the miata since it is newer.
06-22-08, 04:58 PM
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Nice, Wacky.
I'm considering Miata trans internals, and a 4.30 R&P.
The only minor drawback to the Miata internals, is OD is even less than what the SA/FB got, which relates to a higher cruise RPM on the highway.
The advantage of using Miata internals, especially combined with Miata R&P, is the speedo can be regeared to match, using over the counter parts from Mazda, since the Miata uses the same OD tires as an FB, or at least close enough to allow for a speedo shop to calibrate the speedo, to get that last 1-3% accuracy....
I'm considering Miata trans internals, and a 4.30 R&P.
The only minor drawback to the Miata internals, is OD is even less than what the SA/FB got, which relates to a higher cruise RPM on the highway.
The advantage of using Miata internals, especially combined with Miata R&P, is the speedo can be regeared to match, using over the counter parts from Mazda, since the Miata uses the same OD tires as an FB, or at least close enough to allow for a speedo shop to calibrate the speedo, to get that last 1-3% accuracy....
06-22-08, 05:36 PM
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far out. old school thread, really relevant to my life right now! sweet. so I'm rocking the Kia Sportage 4.78's and if I read this right: I can grab a Miata 5-speed use the FB bellhousing and tailshaft, shorten the input shaft, and have a lower final drive ratio?
Am I on the right path or completely pulling stuff from thin air? I live right around the corner from a Miata specific race shop and could definitely grab a tranny off them for the cheap cheap...and probably a 6 pack of the finest microbrew around haha...
ps-peejay-if you happen to see this-your effin nutz. how do you get 25+mpg and still rock the 4.78's? 90 in 4th...! I'm at like 4k in 5th in Atlanta traffic~75ish (no speedo...?)
Am I on the right path or completely pulling stuff from thin air? I live right around the corner from a Miata specific race shop and could definitely grab a tranny off them for the cheap cheap...and probably a 6 pack of the finest microbrew around haha...
ps-peejay-if you happen to see this-your effin nutz. how do you get 25+mpg and still rock the 4.78's? 90 in 4th...! I'm at like 4k in 5th in Atlanta traffic~75ish (no speedo...?)
06-22-08, 06:46 PM
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far out. old school thread, really relevant to my life right now! sweet. so I'm rocking the Kia Sportage 4.78's and if I read this right: I can grab a Miata 5-speed use the FB bellhousing and tailshaft, shorten the input shaft, and have a lower final drive ratio?
Am I on the right path or completely pulling stuff from thin air? I live right around the corner from a Miata specific race shop and could definitely grab a tranny off them for the cheap cheap...and probably a 6 pack of the finest microbrew around haha...
ps-peejay-if you happen to see this-your effin nutz. how do you get 25+mpg and still rock the 4.78's? 90 in 4th...! I'm at like 4k in 5th in Atlanta traffic~75ish (no speedo...?)
Am I on the right path or completely pulling stuff from thin air? I live right around the corner from a Miata specific race shop and could definitely grab a tranny off them for the cheap cheap...and probably a 6 pack of the finest microbrew around haha...
ps-peejay-if you happen to see this-your effin nutz. how do you get 25+mpg and still rock the 4.78's? 90 in 4th...! I'm at like 4k in 5th in Atlanta traffic~75ish (no speedo...?)
The fact that MazdaSpeed sells a race gearset for the FB/FC or Miata, requiring the purchase of the input shaft seperately, would seem to support this info.
Miata input shaft mod info: http://mazdatrix.com/faq/miatainputshaft.htm
Ratio comparason: http://www.mazdatrix.com/faq/ratios.htm
06-22-08, 10:14 PM
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06-22-08, 10:58 PM
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Good to see a more promising transmission. The miata should definatly be easy to get my hands on. On an level of 1-10, how hard would you guys think for an average or just above average mechanic to do thing? Also what do you think my total cost would be?
Sam
Sam
06-23-08, 02:30 AM
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Jeezus- what engine/tranny are you running to be doing 4k at 82mph? and what year miata tranny is it? and what is the rear diff ratio in the miata? sorry to bombard with q's but the wheels are turning-I'm going to be pulling my tranny due to clutch issues here soon, so if I can kill two birds with one stone...you see the logic.
not that its shocking to be doing 4k-im just curious....for a point of reference...
not that its shocking to be doing 4k-im just curious....for a point of reference...