Dear Don a, I recently had a problem with my GMC doing the same thing, and it had the same transmission as yours. The solutions for mine were the shift solenoids inside the transmission case. Because I was driving a GMC van/motor home conversion, the local transmission shop could not fix it, so I had to do it myself. I pulled the transmission pan, ( I had already purchased a transmission pan gasket and filter kit ) and found the two shift solenoids at the bottom edge of the transmission housing, and held on with 2 screws each. I had to buy the solenoids at the local GMC dealer, they cost me $ 39 each. I had the whole job done in 1 hour, and I am slow! P.S. I found I had to tighten the transmission pan gasket several times because until I had the screws REALLY tight, it continued to seep oil. God bless your efforts.
Answers & Comments
Dear Don a,
I recently had a problem with my GMC doing the same thing, and it had the same transmission as yours.
The solutions for mine were the shift solenoids inside the transmission case.
Because I was driving a GMC van/motor home conversion, the local transmission shop could not fix it, so I had to do it myself.
I pulled the transmission pan, ( I had already purchased a transmission pan gasket and filter kit ) and found the two shift solenoids at the bottom edge of the transmission housing, and held on with 2 screws each.
I had to buy the solenoids at the local GMC dealer, they cost me $ 39 each.
I had the whole job done in 1 hour, and I am slow!
P.S. I found I had to tighten the transmission pan gasket several times because until I had the screws REALLY tight, it continued to seep oil.
God bless your efforts.