Whenever you service a transmission, differential,or transfercase, there is always the chance that the unit could coincidentally encounter a problem, and then the failure get some fingers pointed at you or the products used, when in fact it had nothing to do with your method or materials, but instead the unit was going to fail soon anyhow. I have had experiences all over the map in this regard. I flushed and changed filter on a 4L60E in a 1991 car with original fluid at 120k miles or so and after a re-flush a few thousand miles later with Amsoil ATF and addition of an aux cooler and inline filter, that same unit with Amsoil fluid went another 200k miles without incident. I did the same thing with a 2000 Astro and same transmission and fluid (minus the inline filter), and it died within a year. Who do we blame, Amsoil? I mean after all, shouldn't that fluid have extended the life of this unit? Maybe it did some, and maybe it did not, but we will never know, and given the somewhat troublesome history of these units over the years and the known issues (weak spots like the reaction shell and servo piston,etc), I would say it was just bad luck instead. There were parts in failure mode and it was going to fail sooner than later. My trans builder bought a 99 Suburban and never serviced the tranny just to see how long it would go without touching it and it went almost 200k miles. Then he rebuilt it and did all the major updates, etc and now has M1 ATF in it with a Magnefine and original aux cooler.
My point here is to say that I service transmissions as carefully as possible to prevent issues (procedure and good fluid), and as soon in the life of the unit as reasonable to prevent issues as well. I believe this increases the odds that the unit will give a longer service life. In units with known issues, at best it is a [censored]--shoot. The guy who builds manual transmissions for me said it kind of crudely: an AT is kinda like a woman....one day you wake up and for absolutely no reason at all, it's over! I'm not sure I buy that analogy completely, but he had a bad divorce, so probably that's where that came from. I think his drinking had a bit to do with it personally...but hopefully you get the point.
I had another situation where I had serviced the rear diff in a 97 suburban for a friend who takes his boat to the lake a lot and was concerned his diff had bad fluid in it from towing or water-intrusion. Anyway, like 2 days later he called me all concerned as he was hearing and feeling a lot of bad things in the powertrain and thought maybe I had done something to cause the unit to fail or the Amsoil diff lube was bad stuff. Anyway, ended up his 4L60E which fortunately I had not touched, had decided it was a good week to die.
Oil Changer, as much as I know it just seems too coincidental that yours died like it did, I believe that is what may have happened, and I am very sorry it did. That just sucks! It certainly feels better somewhat to have someone to blame, but i would blame GM here instead. And that reman unit was about $1000 too high!
