Originally Posted By: mjk
I tend to think the transmission issues are a bit overblown on internet sites. I just ran into a salesman with an 02 Yukon with over 400k on it.... yes, the original transmission is still functioning just fine. My 2 mechanics do NOTHING that they should do on their personal vehicles, and both are over 200k (with the other at 320k).
It is a [censored] shoot, just like every other transmission out there.
Pulling a utility trailer or a boat 2x a season, is not going to stress the transmission.
I build transmissions for a living, The average life for a 4L60E is 150,000-200,000 miles, Throw it behind a 6.0L....Average life gets shorter. Sure I have seen a few go over 300,000....But not the norm at all.
Getting 400K out of one is very impressive! Either he is mistaken on the actual miles without a rebuild or most of those miles are easy highway miles. Even then the direct coupling of the converter on the highway works away the Stator Support Splines.
Another issue is the way this unit loads the Stator Support Bushing & Sun-Gear Bushing, These get worn....Then the Sun-Shell can no longer run "True" & wallers the splines & they strip, They used to break before GM made the sun-shell out of softer steel.
The 3-4 Clutches have a finite life, They can only cycle on & off so many times, Though full throttle 3-2/4-2 downshifts are the hardest on this clutch.
This unit which is based on a 700R4 was designed in the late 1970's with 150hp MAX engines in mind, If you told those engineers then that this unit had to withstand twice that in a truck that weighs more than a 3/4 ton at the time....They would have started over....
