I haven't had much time with the car
But as soon as I hit 20mph my engine revs way up. This occurs both at WOT and 1/4 throttle, or anywhere in between. my gear shifts are slow... But they do happen.
My motor runs great, fast as hell up to 20.
What should I look for? I just got the car
It's a beat up 85, 147k miles
305V8

 

I think its got a new motor and tranny
torque convertor is probably O-rin-gin-al 1985

 

Sounds like the 3-4 clutches are burnt up. Normally, under light throttle, the 1-2 shift occurs at ~8-10 MPH and the 2-3 occurs at ~20 MPH, which by your description would put it at third gear at the time of slip. Do this: Manual shift from first to second, then second to third and see if it "revs" as soon as it shifts to third. If so, then it needs to come out for a rebuild. Its a very common problem. Better clutches and a TransGo kit will fix you up for a long time.

 

thx.... All my gearshifts are painfully slow... And the 3-4 is virtually nonexistent
I probably will have to rebuild the tranny...

---What problems can be caused by Torque Convertors? How do I diagnose them?