We just got done putting most of the front end back together and didn't touch any of the drive train outside of a transmission fluid flush and filter change. Used a donaldson filter (removed old oring as well), Shcaeffers oil and a new OEM gasket.

Took the truck for a ride and got her all warmed up.

When putting it into the reverse, it stalls, almost like it was putting too much draw on the motor or a clutch dump.....not a dead kick out.

We used Mark K's flushing instructions only we dropped the pan first so we changed the flushing order to compensate for that.

Any idea on what could be causing the stall out?

 

Sounds like a torque converter.

 

It doesn't sound like a torque converter to me. It sounds like low trans fluid, or a loose internal filter. If the filter isn't sitting right in the pump this will happen. So will low trans fluid.

 

It was indeed, low on fluid......3 quarts low by the time it came back from its maiden voyage. Stall fixed!!