Reverse slipping after Engine Install?

[101prf]

I just installed a my engine after a year and a half break. First ride it slips bad in reverse , im not sure if it slips a little going foward or if its just my convertor(only 2800 stall). I don't think its going into OD, it was at 3000 at 60 mph. Trans had no issues when engine was pulled. Fluid is full. I replaced the filter and filled it with Pennzoil ATF(replacement for dexron 3).
I use to run hydraulic fluid in past as recommended by trans builder. Is there anything I could have done while changing filter?

 

[mikestertwo]

You may not have the filter pushed in all the way or you left the old seal in from the old filter causing the pump to suck air giving you low line pressure.

 

[101prf]

The filter was in tight. There is some fine black stuff in the pan, not alot but it was clean about 10 miles ago. Damm I hate my car right now!

 

[Otto J]

Was the convertor in the trans all the way when it was installed?

 

[bison]

Was the convertor in the trans all the way when it was installed?