Tranmission coolers are great but I have my reservations on how well they work. a good friend (Al Norton) had one on his Turbo and watched it like a hawk. Still blew out 3rd gear (and I think it took out 4th too). Al's lasted quite a while actually, I believe because he still had AWD, but he did have big power on his car.

Tom Kerr broke several strengthened and upgraded 3rd gears and ended up having a monster rebuild with a cooler and still his 3rd gear broke after a year.

https://www.6speedonline.com/forums/...mission-4.html

From my talks with Guard and Gbox, the third gear is just a weak link on this gearbox. It's the most commonly replaced gear on the low torque cups too. Since it's the primary gear used on corner exit, it takes a beating.

Along with mine, the common denominator is heavy (over 3000 lbs) Turbo's on slicks with big aero. I think the GT2 that ran one lap broke a couple of gears too and that comes with a cooler. Slicks or Semi-slicks will allow you to put as much hp as you want down early and the gearbox just can't hang for long.

You will be just fine on NT-01, MPSC, Trofeo, Corsa for the long haul. But once you start pushing the car hard and putting that torque down on slicks and semi slicks, 3rd gear is going to go.

A tranny cooler is great, but it will not stop the torque from breaking 3rd gear if you run slicks. Upon inspecting my gearbox after the first break, my gearbox looked awesome, other than 3rd gear. Even the synchros looked great. I finally went with upgraded synchros on my last 3rd gear replacement, but from what I have been told there isn't much I can do different. Of course I make mistakes on shifts too, but that's going to happen when you are really pushing. 3rd gear is just on the consumable regular replace interval at about 10-12 months for a stock one and 16 months for a strengthened one. We will see how long the straight cut gear lasts, replaced it in August. Only 2 events on it so far.

 

I've had good luck with mine. Fluid temps run almost 30F less with the cooler running. Shifting feels a bit less notchy with the reduced temps once the box heats up. I have it set up so that the return fluid dumps directly onto 3rd gear since that is most stressed. Has worked so far.

Are you the same guy that went by heavychevy? Why the name change?

 

I am the same. I still have my other account, this one is dedicated to my car and build. Also embarking on some coaching and business ventures so I needed to separate the two. More details on that later in the year.

Al found that part of the year he didn't even need the cooler as the temps just didn't even reach hot enough temps to make the cooler come on. All the evidence points to it being stress and not heat related for heavily tracked TT's with good power and aero.

Do you run slicks and have big aero on your car? If so, your exact setup should be preferred.

 

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I did a number of track days on mine last year, with suspension and engine mods but no aero. I only ran two days on Hoosiers, (with a best of 1:46 at Auto Club Speedway!), the rest of the time on Nittos, and now have to replace the entire transmission. First and second gears were shot, along with all the syncros and enough damage to add up to 16k just in parts. I have no idea why first would be chewed up, since I have never put the power down in first, but I am the third owner of the car. We decided to put a brand new GT3 transmission instead into the car, since the cost would be the same as rebuilding this one. I just can't afford to track this car much any more with these kind of failures and the cost of parts for these cars! With the price of the transmission and install, this blew my entire racing budget for the year, and then some.





I am going to run in Spec Boxster instead for now, with an occasional track day in the turbo. I love tracking the turbo, but it is way beyond my budget! I am learning why most of the guys in POC run Boxsters, or older air cooled 911's and 944's. Maybe some day when I retire this car from the street, I will take off some weight to make it more durable on the track.

 

Wow, first and second are odd failures to have. Sounds like one of the previous owners was either an avid drag racer or horrible with a manual. I never use first or second on track even on hairpins. Sorry it cost so much but it sounds like you were a victim of previous owners. If you had 16 in parts, those guys must have destroyed the box.

 

You've got me exchanging emls with Geddy now and shopping for new motor mounts and sway bars. Oh this site is dangerous, especially over the holidays with all of this down time.

I've also chatted with one if the guys on our race team (2004 GT3 track prepped) and he is now down to 2800 lbs but now adding a full cage. He already has full aero, Motons, and is fast fast fast!

My car needs aero and a big diet!

 

Good info, but what is the "solution"? My GT2 full race will be hitting the track soon and it will run full RSR suspension and slicks. I've considered putting a "sequential" into the beast, but the Holinger sequential is barely adequate for the 450 hp Cups, let alone a high hp GT2 with big torque. Maybe just say F it and put in a Jerico crash box?

 

I thought I read that the guys who upgraded 997.2 mainshaft + wider 3rd gear all but eliminated 3rd gear failures. However, most of those guys were big power street/drag cars not necessarily track cars... hrm.

 

Great Vid, nice lap. Thanks for posting.

 

I think the solution is to plan to replace 3rd gear at the end of each season if you race it a lot. Or expect to have a 3rd gear failure at some point afterwards in the next season.

The pedal setup on the TT is not ideal either, I wish we had a better solution. I think a cooler, wide gear and pedal setup will buy you some time, but it's going to go at some point. And I'm not talking years down the road, if you do 8-10 or so events a year.


I have tried the wider 3rd gear, and it did last significantly longer, but not sure how the mainshaft will protect the gear. I'm not adept on the inner workings of the transmission.

 

I have tried the wider 3rd gear, and it did last significantly longer, but not sure how the mainshaft will protect the gear. I'm not adept on the inner workings of the transmission.[/QUOTE]

On Kyles GT-R, It was going though 4th and 3rd gear sets, they finally concluded after blowing the best gears sets money could buy that it was actually the main shaft that was flexing causing the teeth to very slightly misalign. Making a thicker mainshaft seems to have fixed the problem so far. I wondering if it could be a similar issue the Porsche box?
How do you think the competition looks in TT1 and ST1 for 2014? Hope we have some more cars, winning NASA Nationals this year in either would have been a pretty hollow victory for me this year with what turned out. Still wish I would have had my ducks in a row and ran since it was on my home track.

 

Hmmm, interesting! That would be awesome if that's the case. I'm certainly going to look into that. May just go ahead and make that swap since my 3rd gear is fresh. I think you have to change another gear as well though if you change the mainshaft, can't remember which though. I think it's 1st, which also means you have to change 2nd because the only available sizes in 1st make the gear speed intervals intolerable. I think......


As for the competition in TT1, it's hard to say bro. TT1 was almost non-existent in the SE last year. Zero events qualified for contingency (in TT1). For some reason a lot of TT1 cars in Great Lakes region ran in TTU. Mid Atlantic has a pretty deep TT1 contingent as does Texas. I optimistic though and think we will get some Texas, Mid Atlantic, Midwest and Great Lakes guys though and will have a good turnout. I am certain though that both the turnout and competition level will be better than it was in Utah last year. Far better.

ST1 will be good, that I would almost bet on. Once the registration opens though we will know by May how it's shaping up.

If I were you, and I could fit it into my schedule, I might consider coming in a week early and doing the Chin Motorsports event the weekend prior to.

 

Please keep me in the loop on the gearbox Dez (and others). I'm building my car for (2) specific highspeed tracks and 3rd is not really even used, but I doubt my situation will be any different once I start beating on the thing. My thinking all along was to run the stock GT2 box initially to evaluate the ratios on these (2) tracks, then optimize the ratios and try my best to strengthen the overall package. Hope my plan works long enough to at least break it in and make an evaluation. John

 

Will do. Have you posted a thread on this GT2 build? If not, why?