A while ago i sent this e-mail to pontiac:

Hello, I currently have a 4T60-E transmission that was recently rebuilt by the dealership. I plan on doing a few modifications to the engine and I was wondering how much torque this transmission can withstand. Also, What are the limitations of the engine itself? I realize that the L36 engine has very little in common with the L67 engine.
Thanks.

And I recieved:

Dear Mr. Me,

Thank you for contacting the Pontiac Customer Assistance Center. We
appreciate the opportunity to assist determine the maximum torque on your
engine.

We have documented the information you provided under file 1-88296206.
Please refer to this file in all communication regarding this matter.
We would also appreciate it if you would provide us with your daytime
and evening telephone number.

First, we would like to advise you that Pontiac does not advise
modifying your vehicle and the number we provide below are to only to be used
as a guide and may not always be applicable under certain conditions.

Maximum engine torque-235 LB-FT
Maximum gearbox torque-final drive 3.06=354 LB-FT

We hope that you will find this information helpful and if you should
need to contact us in the future, simply reply to this message or call
our Pontiac Customer Assistance Center at 1-800-762-2737. Customer
Relationship Managers are available Monday through Friday from 8:00 a.m. to
11:00 p.m., Eastern Time.

Again, thank you for contacting Pontiac.

Sincerely,

Tshimanga Mukendi
Customer Relationship Manager
Pontiac Customer Assistance Center

That dosen't seem so bad does it?
The engine Tq is suprisingly low though.

Credit to them for actually sending you a personalized return letter. When my car died on me on a trip and cost me about $500 for a return trip to retrieve it, all I got from GM was a form letter saying in so many words, T.*.

The 4t60e is considered a stronger tranmission than the 65 which is rated for 280ftlbs of torque? Neither of these tranmissions are great for modding heavely but with proper maintenance and good driving habits they should last a long time. But not as long as the Engine.

In other words...we are all driving time bombs. Feel better?

But like PontiacDad said if you drive "civilized", with the occasional romp on the gas for kicks, you should be fine for years to come.

civilized, as in 0-100 13 seconds at a time?

Of course Rogue!

My tranny has 180K on it, shifts hard, never slips, runs great, and yes, I do beat on it occationally.

:knock on wood:

think about it this way, would you rather have the engine or the transmission last longer? Mine is still original from the factory at 162k miles, and it gets the job done.

im sorta confused....does that mean that the tranny is only rated to handle 5lbs more torque than the engine produces straight from the factory? or is it the other number that its made to handle?

so, it'* not rated for 354 ft-lb like pontiac told me? I'm confused. I told them 4T60-E and had to give them my vin in a form that went with the e-mail.