I was told you may be the one to answer this.

Grand Prix's engine was limited to 250hp vs the 280 planned, apparently due to the transmission. Cadillac has run 300+hp through their trannies for some years. What's the problem installing Cadillac's internals or even the whole transmission into the Grand Prix to solve this?

Inquiring mind want's to know.

 

The Cadillacs all use the 4T80 (except for the CTS), while the W (Monte Carlo, Impala, Grand Prix, Regal) C (Park Avenue) and H cars (LeSabre, Bonneville) use the 4T65.

The 4T80 is larger, heavier and more complicated than the 4T65 - meaning more expensive.

Could a 4T80 end up in a W car? Sure - but that would then require some special work to be done for a limited run of vehicles compared to the overall volume. Just doing some quick math in my head, you are looking at around 1,000,000 4T65's vs. around 200,000 4T80's currently.


So, that leads us to the following problems:

1) Possible volume issues with 4T80 production. Meaning that GM might have a difficult time making enough of them.

2) Packaging issues with the 4T80. Fitting it into a W car might be considerably more difficult than it would first appear - and would certainly require a large investment in engineering development dollars.

3) Added complexity at the W car assembly plants.

4) Weight and dynamics issues.

5) I am unfamiliar with any 4T80 ending up behind (beside?) a 3800 V6. I'm guessing that little, if any, powertrain development has been done with that combination.

6) Increasing the torque capability of the 4T65 significantly over that currently seen is a big tear-up and would require the entire volume of the W cars to ensure that financially it could be recovered. Clutch packs and bands would both have to get significantly larger.



Also, I think the 4T80's days are numbered... for a couple of reasons...

First, 5 speed automatics are becoming the industry standard.

Second, GM doesn't like the dynamics of high horsepower front wheel drive cars. Torque steer stinks and the entirety of the Cadillac line (the main users of the 4T80) will shift to RWD, except for possibly the Deville.



So, in conclusion, high horsepower FWD is an evolutionary dead-end.

FWD will remain the pattern of choice for family cars, but has too many disadvantages to support the luxury cars as they increase in power. This then causes another problem with the performance offshoots of the family cars - the financial squeeze that prevents specialized development of high horsepower models off of their platforms.

Added into this mess are the following complications from a transmission/transaxle standpoint:

1) 4L60 needs more torque handling capacity and will need to add a gear (or two) for the trucks, CTS and Seville soon. 4L80 weighs a freaking TON, and needs another gear also - so that's not a good option for anything other than 2500 and 3500 series trucks.

2) T56 needs to be beefed up or replaced. One thing that is true, but you don't hear about alot, is the ferocious appetite that Vipers have for T56's. They puke 'em out like candy. Camaros chew them up pretty good too.

3) XLR and Corvette further complicate things because of their rear transaxle design.

4) 4T65 needs another gear and higher torque handling.

5) 4T40/45 will probably live on for a while, but will need higher torque handling soon too.