did you do the maintenance on it, scheduled?
full flush time, new tranny filter, drop pan, etc.
you might save it.
a clogged filter starves the pump.
this will destroy the bands, in no time. if bands start slipping.
but it can by 50 other things too, it is after all a complex unit.
thin oil slides past dirty filter?
Slush pump diagnosis
if that dont fix it , there are other parts that can be tried.
and tests.
the are many on car tests for this tranny 3L30 (th180)
Stall tests, pump pressure test, new mod valve, new governer.
to name 4.
cheers.
