I have an '87 Pickup 4WD with an auto trans. There is no slipping, but the transmission doesn't want to shift properly unless I've been driving about 35-40 minutes (which sucks because my commute is 20). When I shift manually (L-2-D) I'm good to go and the trans is fine. The symptoms seem to point to solenoids. I'm going to replace them but I can't seem to find how many I need to purchase. Does this transmission have 2 or 3 solenoids? Thanks for the help.

 

I don't know the answer to your exact question, but what is it about the 35-40 minute warm-up that makes you think it's the solenoids? Wouldn't the ECT sensor be the first place to look?