Transmission shifting very Hard when hot

Got the fuel pump problem solved. Thanks for the replys to my original Post.

When I first got this Van I had the transmission re-built. Supposedly complete. (Did not know that the solenoids were not included in the rebuild) An ASE certified mechanic did the job for me. He has been at our local Gm Dealership for 15 years and is a noted transmision specialist.)

Original symptons were hard shifting throughout all of the gears including overdrive after I ran the vehicle about 50 t0 60 miles. I could stop the van and kill the engine and crank it again within seconds and it would go another 60 or so miles before it would start shifting hard again.

The mechanic added a heavy duty transmission cooler when he did the rebuild for me.

I have put about eight thousand miles on the van since the rebuild and now it is doing exactly the same thing again.

Could it be one of the solenoids in the transmission?

I can't ask the mechanic I used because he has had illness fall upon him and is gravely sick at this time.

If someone has an answer or suggestion please give it to me.

Thanks, temeek