Hi guys, I need the big dogs experience here!

Following my gearbox issue I have 2 solutions:
-swapping my destroyed gbox with a brand new oem one from the factory (about 8000€ but cheaper vs rebuilding it with oem parts)
-building or buying a BRM style 996TT gearbox (I want to keep the 4wd)

Some folks here tell me the oem one is bulletproof, mine might had a problem (?), so, who here runs >800lbs torque with his oem 997T gbox? For how many miles?
Thank you for help, I don't want to spend stupidly some hardly earned money nor spending springtime and summer looking at my broken toy!
P.

 

OEM 997 trans is bullet proof? What?

 

If you want used 997tubro gearbox in very good conditions .. please let me know !!

For your question , we built many 997TT with 6speed OEM gearbox (ES1200-ES1000h) never had a issue ! Only clutch/LWFW !!!

Why you do not go big and run seq ??

 

The 996TT, 997TT turbo stock transmissions are far from being bullet proof. Since they are a modified 5 speed to include the 6th speed, the 6th gear in particular starves for oil under hard acceleration especially in modified high horsepower cars, and wears out quite quickly. In addition the 3rd gear synchros tend to wear out quickly.

If you keep it stock, change the transmission fluid every 6 months to 1 year depending on how you drive it and if you have the cash have upgraded synchros before they go or worn down thus sending chunks of metal bashing around (even though they are brass/copper, they still can do damage).

 

Thank you, but I feel not anymore confident with the 997 gearbox, it is the second time I break it (bearings) in despite of fresh oil etc...
I very often (each time I run the car) log it or WOT from 4rth about 2000rpm or play rolling races from 3rd (never from 2nd) and it puts very much load on the gearbox. My car puts >1000Nm before 4000rpm and 1150 about 5000, probably too much for it.

I don't truly know seq (hollinger), and it is probably too expensive, I'm thinking at building a 996TT gearbox.

 

My synchros failed because my shafts took axial clearance when the bearings get destroyed, and all the gearbox failed...
I believe the helical cut axial resultant strenght is guilty under big load.
Thanxs for input.

 

what do you mean " built many 997TT with 6speed OEM gearbox (ES1200-ES1000h) " ? built motors with OEM trannys? or change any components inside the gear box ? synchos or ?

would type of oil aid in any way ? OR go oem ? redline ?

 

There is not a tremendous difference internally between the 996 and 997 turbo gearboxes. One of things to consider would be the oiling system in these gearboxes though. It would probably be a good idea to consider going to an externally operated system that would give you more flow overall.

What kind of power are you running in your car currently? When your gearbox failed, what part of it actually caused the failure? Was this a gear failure, a bearing failure, or ring and pinion fatigue?

I think I can offer some advice that might be helpful to you in this, but I need a bit more detail.

Erik Johnson
(720) 899-6005 phone

 

Hi Erik,

I'm thinking about an oil cooler with an electric motor.

The car puts about 850lbs torque and 1000hp (4.5' 60-130 with 1 or no shift, 3rd + 4rth pull or 4rth gear only, 12.8' 60-186) and always runs at this level, it is not a "glory" tune.

The both failures were dued to bearing failure first which caused excessive longitudinal clearance in the shafts (shifting became "chewy") and destroyed synchros and pignons with the metal parts in the oil.
Nevertheless the gears did not pop out, at driving the gearbox became a bit noisy and cracked at shifting, but "worked".
That's the reason I believe the short cut gears which do not generate any axial strength on the bearings are the way to fix.

Notice the car is a (dry) week end toy and everytime it goes out I play/run rolling pulls from 3rd and 4rth gear to 5th (rarely 6th, no need to run so fast, rarely from 2nd cause excessive spinning and you need to shift 1 or 2' after WOT, no launches as well, I hate that)

 

Straight cut gears would certainly help with the axial loading being put on the bearings. Another thing that would help would be a better bearing retainer plate. The stock unit tends to weaken and can fret out.

There will quite a bit more noise with the new gears though so keep that in mind. That said it is a pretty good trade off in your situation if you don't mind a bit of whine. I would stay with the synchronized gears rather than the dog ring style, as these will require far less maintaining.

Matt over at Guard Transmission make a wide variety of these gears, he is located here in Colorado. Given your HP you might want to also have the gears cryogenic treated, this would stress relieve them a bit better and give them even better life, but I know Matt might have some thoughts on this too. I would probably just go with 3rd-6th so that you don't have to change out the shafts too.

Let me know if you have additional questions I can help with.

 

hello

what I meant is the 997tt gearbox (internals) can hold the power !!! But we do racing from 3rd gear only !!! So we do not push too much load in 1st and 2nd gear ! Yes all the internals are OEM even the oil is OEM ! Only clutch /LWFW change !!

 

My car is for sure less powerfull than an ES1200, I dunno how much torque do you put? How on earth can mine fail 2 times and yours hold?
(Notice a LFW with the strongest Sachs clutch from FVD did not hold but was slipping, I had to go with a twin discs clutch)

 

hey ,
i will tell you why !!
We do street racing most of time , the cars am telling that is 997tt and GT2 we only roll from high speed 120km/h or 140km/h so rolling from 3rd gear !!!! As far as the clutch , we ran ERP or SRM !!! Both hold fine !!!

Also to give you an idea , when I swap my Tiptronic 997tt gearbox with 6speed 996tt OEM gearbox (so I can modified it since it's 996tt 6speed) !! The gear did not hold more than 1 month all gears damaged so ESmotor ordered a custom gears with taller ratios from billradar !!!

The point in my opinion 997tt gearbox is much better than 996tt as its hold the power and TQ but only when getting the load from high speed !! Not in 1st or 2nd gear !!!

 

Bill Rader recommended in my case not to go over 950ft lbs of torque on the 997 6speed. He also said it is quite a bit stronger than the 996 trans. Second hand info, process accordingly.

 

To Youssef:
This is also my use: never launching, always rolling starts but often from the 4rth gear as my times are the same from the 3rd + shifting vs from the fourth.
My engine is better at torque vs at pure power.

To Rix:
I follow your thread and noticed our goals are about the same, nevertheless you push the developpement far further than me.
You want early torque as well and it is imho the gearbox killer, I had Bill (and Matt at Guard) as well and went to a built 996TT gearbox.
My torque is about 850lbs at 5200rpm with already 736lbs at 3600rpm.