http://mymonte.com/discussion/topic/...ranny-held-up/

I've kept an eye on this situation and have notified other people about it, so it might be worth noting.

GM thought the Series 2 3800 - L36 (230lb-ft) would be fine with the 4T65E, which is rated for 280lb-ft

GM thought the Series 2 3800 Supercharged L67 (280lb-ft) needed the 4T65E-HD, which has a larger differential and shorter axles, and is also rated at 280lb-ft.

GM thought the Northstar 4.6L DOHC V8 (295lb-ft) needed the 4T80E, which is rated for 300lb-ft.

But for some strange reason, GM thought the 5.3L LS4 (323lb-ft) could get away with just the 4T65E-HD, which is rated for 280lb-ft. Do the math.

And as a result, they're failing by the boatloads. So if you have an LS4 powered Monte Carlo SS or Grand Prix GXP, keep an eye on your transmission. Whether you beat on it or drive it like a grandma, it seems that it will be guaranteed to fail before 100k miles hits.

That'* strange...

I'm counting my blessings that my tranny is still going strong, no issues yet nearing 100K. It'* all highway miles, but I still beat on it every now and then. If it can just hold out a while longer I'll have enough back to replace it with something I won't have to worry so much about.

F40 swap is the route I'm taking when the 4T65E-HD in my L67 swap in the regal grenades itself.

6 speed manual from the G6'*. That dual-mass manual transmisison can take up to 400lb-ft of torque and do it reliably. That'* enough to satisfy your craving for L67 power, and its lighter to boot.

Are you sure your facts are straight? The 4T65HD in the 5.3L cars is a different transmission than the standard 4T65HD we have. Starter is on the trans side, chains are HV-093 (stronger) etc.

To my knowledge, a few things might be slightly different to accomodate the new engine, but overall, the transmission is pretty similar, and it is failing like a 323lb-ft engine would when bolted to a 280lb-ft transmission.

If it was significantly different, I have a feeling they wouldn't still be calling it the 4T65E-HD. In any case, the thread should speak for itself.

It should be obvious that GM cut corners where they shouldn't have. Why would they use the 4T80E in the Northstar and not in the LS4 cars? No matter how you look at it, the 4T65E is a lightweight compared to the 4T80E.

Here'* what I found

http://ls1tech.com/forums/ls4-front-...-4t65e-hd.html
http://www.clubgp.com/newforum/tm.as...heck=716034995

Apparently those upgrades weren't enough.

I'm aware they weren't enough, I was saying that the trans had been beefed up from the model we are all used to talking about. The L67 rips our version to shreds w/o being modded. And that'* with a lot of torque management in the programming.

My point was only to mention that the version used for the LS4 5.3L is different in a number of ways and may have a higher rating. Between the V8 chains, and the upgrades from 03 (VB and 4th clutch hub) our transmissions can be much rebuilt much more stout and capable of handling more power than stock.

Then again.. I've killed too many transmissions to say much about the longevity, the only things I can tell you is I've broken every little stuipid part that should never break and others don't usually have any issue with.

In that regard I agree with you. I didn't know they upgraded it, but its a pity that it wasn't enough. My guess is that the 4T80E wouldn't have fit in that engine bay. The way I see it though is that it was too big of an engine to put into a FWD w-body anyway.

Why haven't you swapped an F40 yet? That transmission can take a lot of power.

I've up around 450chp. Not looking to shift the car beyond yankin back to second. The next car the motor jumps into will be close to a 1,000lbs lighter which could solve my issues.

I don't know a whole lot about weight in regard to transmissions, but does it make a difference how much your car weighs? For example, this L67 that'* going into my Regal...the Regal weighs right at around 3200 with the weight reduction I have done (factory came at 3232), while the GP GTP weighs 3450. You think that'* going to help my cause much?