Hi guys new to the forum. The story is my gf has a 95 blazer 4x4 and after she gets off the e-way after about half hour of drivetime the trans begins to slip when it is trying to shift from drive to overdrive, at about 45mph. I have checked it and the fluid does seem excessively hot. Could it be that the trans oil cooler is not working properly? When it is cold it shifts fine. Also it seems to need a half quart of fluid every 3 weeks but i'll be danged I can't find a leak anywhere?? Is it possible that it is overheating and burning the fluid? Any opinions would be appreciated, I guess all I can do is try changing the filter and fluid....

 

The problem will likely not go away with a filter/fluid change.

Possible causes from wear include (from my 4L60E ATSG manual):

• sticking valves - 2-3 shift valve train, accumulator valve, 1-2 shift valve train, or 3-2 shift solenoid valve assembly
• 2-4 servo assembly - damaged servo seals, damaged piston seals, or a plugged/missing orifice cup plug
• Case - 3rd accumulator retainer & ball assembly leaking, 3-4 accumulator piston seal damage, plugged/missing orifice cup plug, or a restricted oil passage.
• A worn 2-4 band assembly.

There are other causes listed as well, but since you have not recently rebuilt this transmission (I assume), the likelihood that parts have mysteriously disappeared is slim. LOL

The last cause is my bet as to what the problem actually is, but a seal or passage restriction of some sort may be a cause as well simply due to the age of the transmission.