A bit disheartening when a 2004 1/2 ton with tow package transmission fails with 49k miles on it and having done no towing. At the shop now. Lost all forward gears with a god awful whirring sound, only had reverse.
The 4L60E can be a source of failure. I'm crossing my fingers on mine.
If it goes, the first thing I'll do is swap in a 4L80E. It would seem that the 4L60 and even the 4L65 can only handle about as much torque as teh 5.3L Vortec will throw at it and is continually on the bleeding edge of its limits.
From what I've read, the 4L60E can handle up to around 350 ft/lbs of torque. On my '95 Jimmy with 195 HP and only 260 ft/lbs of torque the 4L60 ran for
150K miles without even a hiccup.On the AV/Silverado/Suburbans, however, the torque is up around 330 ft/lbs.
A 4L80E, OTOH, is designed for trucks up to 8000 GVWR and 440 ft/lbs of torque.
Just as a preventative measure, I flushed my tranny fluid at around 20K miles on the Avalanche and plan to put in a B&M deep transmission pan as well as a tranny cooler at around 40K miles.
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