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Racing Transmissions

Old 08-22-11, 12:50 PM
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Racing Transmissions

Hey fellows. Just thought I would share my experiences with road racing and transmissions.
For the first five years of road racing I ran the stock TII gearboxes. There were a few good things and a few bad things. I know you can get a version of the T5 with a better shifter offset, but to date I have yet to find one.

Stock TII:
The Good:
-Bolts right up
-Can handle up to 300-350 rwhp
-Reasonably light
The Bad:
-Third gear blows after a while above 350 rwhp. (We've blown up a number of them in FC's and FD's)
-Shifter is sloppy
-Gear selection is horrible (3.483, 2.015, 1.391, 1.00, .719) (this is the later TII and FD ratios)

T5:
The Good:
-Easily available adapters
-Gear ratios in the Ford motorsports gear box are better (2.95, 1.94, 1.34, 1.00 .63)
-Fits in transmission tunnel with hole cut for shifter further forward and goofy shifter extension)
-Can fit a Pro 5.0 shifter and shifts well at lower rpm.
-You can buy them new for $1300 and they are easily sourced.
The Bad:
-You need to cut a hole for the shifter
-Doesn't like shifting at high rpm (which can lead to bent shift forks)
-Can hold about 350-400 rwhp before you blow 3rd gear. (again, after a while at power)
-You need to build a custom driveshaft and transmission mount
-You need to buy/build a bellhousing adapter and a new clutch
-You have to remove the pinion bearing from the eccentric shaft or cut down the input shaft

T5 with G-force kit:
The Good:
-Easily available adapters
-Gear ratios are excellent (2.42, 1.53, 1.23, 1.00 .90)
-Fits in transmission tunnel with hole cut for shifter further forward and goofy shifter extension)
-Can fit a Pro 5.0 shifter and shifts are amazing.
-You can buy them from G-force for around $3500.
The Bad:
-You need to cut a hole for the shifter
-Can hold about 400-450 rwhp before you blow 3rd gear.
-You need to build a custom driveshaft and transmission mount
-You need to buy/build a bellhousing adapter and a new clutch
-You have to remove the pinion bearing from the eccentric shaft or cut down the input shaft

Those are the transmissions I've had experience with. I just took 3rd gear out of my G-force T5 at the recent Edmonton Indy Race. I was running 18 lbs of boost and putting down about 460 hp at the wheels through Yokohama 280/650/18 slicks (they don't spin). I'll be rebuilding the T5, for the second time and starting to think about other options. I'd like to know what experience other people have ahad with the T56, Tremec TKO, etc.. I'm personally leaning towards a Jerico, but the $5K for the transmission and around $2K for the adapting hardware are giving me pause. I've also considered the G Force GF-5R as an option, but the costs are pretty much the same as the Jerico.

Cheers,
-Trent
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Old 08-22-11, 04:58 PM
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wow, nice timing Trent... I was actually just looking for this info over the weekend. Picked up an FC last week to use next season as I am retiring the Evo after this fridays event.

Such expensive options, might keep my cheap butt around 300 horsies so I can use a more economical transmission.
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Old 08-22-11, 05:39 PM
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I just lost 3rd gear for the 3rd time after turning up the boost a little bit. From 12 psi to 14 and boom lost 3rd gear at about 7500 rpms. It was really REALLY HOT. I'm thinking if I add a trans cooler it'll keep things from expanding as much or keep the gears tighter under load. Have you tried running a good gear oil cooler on any or all of those boxes?

This was a nice trans, shifted well w/ no noise so it definitely sucked
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Old 08-23-11, 02:44 AM
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trent

have you considered the supra turbo getrag tranny. they can hold 1200 horsepower, have close ratios, 6 speeds, positive shift action, and have been proven in australian touring car. And you won't be changing dog rings all the time. And there are several sources for an adapter. I think the trannies run about $700 -$1500 used. I was going to go this route at one point.

The tremec/ t56 is a great tranny but the ratios won't work with your car, (not even my car) unless you have 5.3 rear gears maybe?

This is a weird year . I finished the car late june , I've run 2 races within a month and now i'm already taking the car apart for next season. I've got a full page of changes to do.

wouter
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Old 08-23-11, 08:16 AM
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I like my 4spd Jerico. I don't think you need to spend $5k on the box and $2k on misc, think you can do it for much less. Used 4spd boxes are readily available, the adapter for the bellhousing isn't much, add a driveshaft, new clutch disk and the mount can be done by modifying the stock mount, less than $1k for this. The $7k is more what I would expect Taylor to quote for a 5 speed and you went new on everything.
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Old 08-23-11, 09:34 AM
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Im doing a Gforce T5 in my FD. WIth a bit of searching, you can pick up a T5 from a 82-83 Nissan 280ZX Turbo, which has its tail housing 4" further back than all other T5s. This eliminated the need to cut up your trans tunnel and/or run goofy shifter extensions. There is one problem with this model T5 though, the tail housing will need modified to fit the Gforce gearsets, as the Nissan output shaft is a smaller diameter than the mustangs. I found a shop that will do the modification for ~$300. Im not done with the install as of yet, but I dont see any more issues. Sure its a bit of a hassle, and for a race-only car I guess most wouldnt care.. but I wanted to avoid any cutting of my FD.
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Old 08-23-11, 02:16 PM
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I run a heavily modified, track only 93 FD (410 RWHP) and am on my 4th OEM transmission in a calendar year. While I could continue to source OEM transmissions from C-list for ~$300, I grew tried of not knowing when not if the box would break. To resolve this I am just finishing up a G-Force G101A 4 speed conversion. I will be testing and racing next week at Infineon.

If anyone is interested I could write up the information I have collected regarding this swap.

Guy
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Old 08-23-11, 02:29 PM
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Originally Posted by finger lock View Post
I run a heavily modified, track only 93 FD (410 RWHP) and am on my 4th OEM transmission in a calendar year. While I could continue to source OEM transmissions from C-list for ~$300, I grew tried of not knowing when not if the box would break. To resolve this I am just finishing up a G-Force G101A 4 speed conversion. I will be testing and racing next week at Infineon.

If anyone is interested I could write up the information I have collected regarding this swap.

Guy
Guy,
Sorry to hear about the failures You are seriously a track addict

Do you have any idea what is failing and do you think a cooler would help or do you believe it's strictly a torque power problem and temps are not the issue?
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Old 08-23-11, 02:39 PM
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If/When my built tranny goes, I'd seriously consider the Supra Getrag conversion. That's a nice transmission, and shifts a lot better than a T56.
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Old 08-23-11, 03:01 PM
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Originally Posted by Fritz Flynn View Post
Guy,
Sorry to hear about the failures You are seriously a track addict

Do you have any idea what is failing and do you think a cooler would help or do you believe it's strictly a torque power problem and temps are not the issue?
Fritz,

The majority of my transmissions failures have involved 3rd gear, but I've also buzzed a lower main bearing. I don't know if temperature is one of or the major cause for these failures. I have tried several fluids (Redline MTL, lightweight shockproof, and non-synthetic) and have had similar failures.

John at Evil Genius Racing, he rebuilds all transmissions for Mazda USA, told me I was doing pretty good when I got 6 weekends out of my rebuilt transmission. He said they just can't handle the power.

Guy
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Old 08-23-11, 04:40 PM
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Originally Posted by finger lock View Post
Fritz,

The majority of my transmissions failures have involved 3rd gear, but I've also buzzed a lower main bearing. I don't know if temperature is one of or the major cause for these failures. I have tried several fluids (Redline MTL, lightweight shockproof, and non-synthetic) and have had similar failures.

John at Evil Genius Racing, he rebuilds all transmissions for Mazda USA, told me I was doing pretty good when I got 6 weekends out of my rebuilt transmission. He said they just can't handle the power.

Guy
That's what I was afraid of. Basically it's just a case failure under load so lowering temps probably won't help.

I think I'll drop power a little, loose some weight and put in the 4.3 I have laying around.
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Old 08-24-11, 07:49 AM
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My OEM trans spikes to 230deg. I believe that most of my temp problems are the proximity to the exhaust. even though i have at least 6" of clearance, i think the heat from it under boost is the culprit.

I'm on my second trans for the season. not sure how long this one will last.
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Old 08-26-11, 11:46 AM
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What I'd like to to is add to the list I started with other gearbox options and rough costs to do it properly. A few guys have put forward the Supra gearbox as an option. Where is a good source, who makes an adapter kit? The Tex 101A or other used Nascar-style four speed seems a good option as they can stand up to the horsepower and are available. any good sources for the adapters?
I know Wouter (racingdriver)(700+ hp 20B) runs a Jerico and he loves it. I also know a local fellows who runs a very well built 300Z with the Jerico box and he had a failure where it lost all the fluid. Jerico put it back together for him for a under $300.

Best,
-Trent
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Old 08-26-11, 12:08 PM
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Originally Posted by TrentO View Post
I also know a local fellows who runs a very well built 300Z with the Jerico box and he had a failure where it lost all the fluid. Jerico put it back together for him for a under $300.

Best,
-Trent
thats what Im most interested in... its racing so things will go wrong. But when a company stands behind their product it makes it worth a little more
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Old 08-26-11, 05:56 PM
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The ratios in the Getrag V160 fro the Supra don't look that appealing for a road race / time attack car.
The ratios are:
First gear: 3.827:1
Second gear: 2.360:1
Third gear: 1.685:1
Fourth gear: 1.312:1
Fifth gear: 1:1
Sixth gear: 0.793:1

First is way too tall and I'd even question second. The jump to fifth from fourth is huge as well.

This is considering that before the Indy I've only used first gear in my G-force box for starts and getting it on and off the trailer. All the corners on my normal tracks let me stay in second.
For the Indy, I was using all five gears and nearing my top speed of 155 mph. This means my gearing is quite well suited to the track as I'm able to make effective use of all gears and accelerate as quickly as possible.
If I could change anything with the T5 gearing I would move first up a bit more and move third down just a hair.

Here's an image comparing the V160 to my G-Force T5


-Trent
Attached Thumbnails Racing Transmissions-trans-v160-vs-t5.jpg  

Last edited by TrentO; 08-26-11 at 05:59 PM. Reason: adding content
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Old 08-26-11, 11:13 PM
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here are the ratios for my jerico

jerico supra- Ignore 1st

2.61 2.36
1.9 1.69
1.56 1.3
1.23 1.0
1.0 .79

I run 3.73 and 3.9 's in the back. If you ran 4.3's your 1.69 would be a usefull gear equivalent to my 2nd gear. ...maybe ?
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Old 08-29-11, 08:37 PM
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When You say that the T5 likes to bend shift forks at high RPM shifts, Do you mean that hard shifts bend them, or just the fact that the RPM's are so high will bend the forks? Also when you swaped a T5 did you use the T2 T/O bearing or T5 T/O Bearing and retainer?
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Old 08-30-11, 12:00 PM
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I said the T5 likes to bend shift forks due to the synchro gearbox not wanting to shift well at high RPM. When you add in an excited driver, you get bent and broken shift forks. I think this issue will be common with most non-dog gearboxes as they are not designed for 8000 rpm shifts.

-Trent
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Old 08-31-11, 12:03 PM
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Wouter brings up another issue. With the Jerico or GF-5R I'll need to replace the rear end with a shorter gear as the 5th gear will top out as a 1:1, as opposed to my current .90 overdrive. That's going to add more cost to the equation. I'll likely have to source an 8.8 rear end and build that up or just do a quick change.

-Trent
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Old 08-31-11, 07:33 PM
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You can overdrive a Jerico box. It involves flipping the 3-4 lever off the side of the trans essentially making the pattern go from 1st to 2nd to 4th to 3rd. 3rd gear is the overdrive gear.

I have my Jerico set up with these ratios,
1st 2.176
2nd 1.392
3rd 1
4th .849
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Old 09-01-11, 12:48 PM
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I was thinking about the Jerico 5-speed. I don't think it can be overdriven in the same manner.

-Trent
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Old 09-01-11, 05:01 PM
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Originally Posted by Donovan N. View Post
When You say that the T5 likes to bend shift forks at high RPM shifts, Do you mean that hard shifts bend them, or just the fact that the RPM's are so high will bend the forks? Also when you swaped a T5 did you use the T2 T/O bearing or T5 T/O Bearing and retainer?
We used the TII throw out bearing, with the TII clutch fork.

-Trent
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Old 09-19-11, 08:23 PM
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Trent-

I try very hard not to add up what I spend on the car, but here is a rough estimate...

Refurbished G101A from G-Force with Long shifter and 3/4" Mazda adapter plate, installed 1.923, 1.538, 1.239, 1.0 gears - $3800

Busted Turbo II transmission - for bell housing - $50

Turbo II pressure plate and custom clutch disc, throw out bearing, pilot bearing and seal- $450 (ACT extreme, 6-puck)

OEM differential brace- Samberg - $500

Custom drive shaft - $500 - you could save a couple hundred here by getting some Nascar drive shaft parts off Ebay - my build didn't have the time to spare.

Turbo II starter - $100

Large issues to overcome...

- we had a clearance issue with the input flange of the 3.9 diff and the differential brace.

- custom exhaust would not clear the differential brace.

We ended up cutting the Samberg differential brace and used the various pieces and made a new torque arm. This took about 14 hours of an fab time...

Also you need to fab a mount for the tail of the transmission - this transmission bolts up to a standard 2-bolt Chevy, rubber transmission mount.

Oh yeah, you need to cut a BIG hole in your transmission tunnel and then fab a cover after the transmission is installed.

After one weekend with this transmission on the track I can say it shifts very fast and feels real solid. I look forward to racing my car and not worrying about when third gear is going to fail.

Guy
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Old 09-22-11, 06:49 PM
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has anybody used a GM mucie 4 speed or T10 transmission? a Muncie M21 has 2.2 ,1.64, 1.28, and 1.0 gear ratios. A Borg Warner Super T10 has 2.43, 1.61, 1.23, and 1.0 gears. Both can be biught new for less than $2000
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