You already working on it, might as well do it right or your just going to be doing it again. I wouldn't do the output shaft, but I would do the input shaft. Keep the current gearing, do the LSD, TC-300 as the major upgrades in the kit and you should be fine. That 2 part combo will more then likely save a stock input but is not foolproof and as the input shaft is the last part in the trans its labor intesive to replace. Upgrade to the raybestos beefier clutch packs and check your fluid monthly and enjoy it.

Yeah, the 4T65E HD does have alot more issues than the non-HD version.
I believe GM has some a bit of updating to the 4T65E over the course of it production years, but still needs some doctoring.
Can't say I've anything on the 04 GTP trans though.

According to the Pontiac website,which has corporate info on the upcoming Grand Prix V-8 GXP,they are going with a beefed up version of the 4T65 tranny,along with the tap-shift, quote:"The transmission is strengthened to handle the prodigious[wow,fancy word]torque of the V-8 engine",............'who knows' how they will 'beef' it up to handle the extra torque?!?

what about the DP transaxle? The price looks good and it has a warranty.does anyone have any info?

Are these problems happening on stock bonne'* et al, or mostly on modded ones?

One thing to consider is the output of the cars that are thrashing these HD trannies.

Rogue has a dyno somewhere that shows my mods at @320ft/lbs, he should be due for another dyno soon with the gen 5 and 1xs cam

My last dyno showed 425 at the crank, i'm guessing after my latest mods its close to 475-480. Ole girl is holding up well under the circumstances

The stock torque of an L67 is rated at 280ft.lbs, but it is actually around 320 or so, so thats why they kill trannies. The tranny is a strong tranny, especially when beefed up. The stock one in my dads GTP lasted 22k and was still working well when we got a ZZP Tranny put in, and his car was modded from day one and had a shift kit. He had 50+ 12 Second passes on his stock tranny, and the only thing that ever broke was a halfshaft and a few Intense differentials. The transmissions can handle the stock power just fine and for a while, thats why the torque management is in the computer, GM was thinking when they put it there, but people get rid of the torque management (can't really blame them for that) and mod the car and all of the sudden the tranny is taking a real beating. Our SSEi has over 120k on it and it still has the stock tranny and it seems to be holding up good (knock on wood). It has been modded since it had about 30k on it and its not heavily modded, but it definately has a few mods. It is driven hard, but not really abused, and its only ever made 2 passes at the track. The transmission does exactly what its meant to do. Once you start modding the trannys go fast, because it really doesn't take much to add 100ft.lbs. of torque to a L67.

The GTP put out 357.4 ft.lbs at the wheels on the dyno, but it would've been higher if we could've started at lower rpms. The highest torque was when the dyno first started and it slowly went down from there, if it would've started 1000rpms sooner the torque would've been even higher I think. (probably around 370ft.lbs) 357.4ft.lbs at the wheels, assuming 20% drivetrain loss, is 447ft.lbs at the crank. Add another 1/2 lb. of boost and 6 degrees timing to that and the difference would be even more now. I'm guessing its putting out 475+ft.lbs and the tranny is taking it with no problems.

Shawn

My 2000 SSEi is 100% stock...and the tranny came apart at 56K miles.