Automatic Transmission SLIPS in passing gear.

[Dean_Fuller]

Just replaced the TT in my 89 car. New torque converter bearings and new pump seals. Everything felt like it went back together well. Had a little trouble seating the pump but after a little turning it seated well I thought. Replaced the fluid with new and filter as well.

I need to state that the modulator has a very slow vacuum leak. I replaced the main vacuum line and tested the line it self and it holds vacuum well...but the modulator itself does not.

At first the only gear that seamed to work well was reverse. ALL forward drive gears slipped badly...so bad it would not pull the car up an incline.
Adjusted the modulator 2 full turns clockwise and it pulled MUCH better. After a test drive it holds gear too long and the up shift is harsh but it felt smooth at highway speed.

After a longer test drive today ( 30 minutes) ...I get a vibration above 60 MPH on the highway. This vibration fluctuates slightly...almost like a wheel bearing but nothing below that speed. The harsh shifting is still there but now if I hit passing gear the transmission slips badly. Motor RPM increases fast but of "pull" then a catch as the rpms lower.

I noticed the torque converter is from a 87 model ( written on it with paint and the word "good" ) so it was replaced at some point. I have paper work that states a replacement transmission was installed in 2002 at one point. I can assume the converter was replaced then.

Here is my questions...

1) Can a leaky modulator cause all this?

2) Can a bad converter cause this? When a converter goes bad what are the signs?

3) How can I test to see what the problem is?

4) Does the fact that all forward gears could pull nothing after install tell me anything?

5) Could I have screwed something up by removing the converter and pump??? ( the new seals are not leaking so far)

Automatic transmissions are above my head. The fact they work at all is magic as far as I know.

Any feedback will help. not sure what my next move is. The only thing I KNOW is not right is the SLOW vacuum leak in the modulator. I can fix that but I'm not sure that will cure all these issues.