Quote:
Originally Posted by thePill
The Hydra-matic 6L90 used in the CTS-V and the ZL1 is probably one of the best automatic transmissions for the price associated in those applications. This doesn't mean that there will be zero issues with them and the lack there of are probably due to the total amount that are actually produced and sold.
GM rated the CTS-V's 6L90 at exactly the torque and curb weight of that vehicle, any additional weight or torque is in fact "pushing the limits" of the transmissions rating of 551lb ft of torque at 4250lbs. This doesn't mean the transmission will instantly break after that, remember the GVWR of the CTS-V is about 5200lbs so the transmission should be capable of about 700lb ft at the actual curb weight... Which is why there were no adjustments made for the CTS-V wagon because the curb weight and GVWR was within 250lbs of the CTS-V coupe. The ZL1 on the other hand needed stronger output shafts and rear housing to accommodate the extra 5 torque even though the ZL1 is about 35lbs lighter than the CTS-V coupe (automatic weights pending of course). The 6L90 is a massive transmission, it weighs 209lbs in the CTS-V so it is about 25-30lbs heavier than the TR6060 MG9.
Think of a transmission as a referee in a match between "Force" (engine torque) and "Resistance" (weight with traction being a resistance modifier). No two matches are the same even though the conflicting participants remain constant. In most cases, the clutch, drive shaft, universals and countless other things in relationship to the transmission are made to give before the more costly internals of the transmission do. If there is in fact an internal issue then it could be a compound issue with that particular transmission that caused the failure.
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Excellent post
Thanks for the technical data, too, guys!!!
