91 Blazer rebuild transmission won't shift right

[blblair]

My sons 91 Blazer would seem to slip out of gear when going to third gear. We had the transmission rebuilt. We got it all put back together, and at first, it would not shift into the higher gears. I talked to the person who rebuilt it and he said that it had air pockets and to keep taking the rpms to high levels and keep going through the gears. After spending two hours on a jack with rear wheels off the ground, it finally shifted, but it has problems and will not shift all the time and usually, you have to get the rpms way high before it will shift.
Does anyone know anything about this? Is the transmission guy telling me straight? Im afraid that I will blow the engine if I keep running it to try to get it to start shifting. Please help. Also, it is a 4x4

[BlazerLT]

Take it back to the guy and have him fix it.

He is just trying to bullshit you.

[Mikado14]

Do you have the proper oil in it? Is the clutch dragging?

[blblair]

It is an automatic, and he said he put all new parts in it when he rebuilt it. It has the proper fluid.

[BlazerLT]

Originally Posted by blblair

It is an automatic, and he said he put all new parts in it when he rebuilt it. It has the proper fluid.

Still, this is a warranty job, his work, he should honro it.

[s10blazerman4x4]

i agree with lt
if its under warranty have him fix it