The car bucks going 50+mph...sometimes making a 'groaning noise'. I assumed it was the tranny slipping trying to get in OD, but when I run the car in 3rd theres no difference. So I thought maybe its not the tranny. A few weeks later I got a code saying catalyst inefficency. So I replaced the catalytic converter last night..No fix.
So now I bought a tranny filter/kit and will drain the fluid to look for damage and add some lucas detergant.
Any idea what woudl cause the tranny to make nosie and buck like that?? It doesnt sound like the TCC since it still does it in 3rd gear. Could it be a bad valve body?
What are some things I can look for with the tranny pan removed?
Is the valve body pretty easy to change?
Any suggestions!??? Gotta get this one fixed fast!

If it goes away in third, it may be the TCC.

Whoops..that was a typo..Im not sure how I typed it like that. Ill fix it..
I drive the car in 3rd gear with absolutely no difference. Same bucking/jerking at same speed.

Just drained the tranny..Clean as a whistle..No metal flakes or burning..

fuel filter good?

I shoudl definitely change the fuel filter. In fact I bought one months ago and just never put it on.

Drained the fluid..Everythign looks fine in the tranny. In fact, Im sure someone just flushed it. Maybe they cleaned outall the metal..Who knows. Put the Lucas stuff in..Takes forever to pour in..Its like glue..No wonder it works so well. Ill take it out tomorrow afternoon and see what happens. I got a good feeling this will help minimize the problem alot.

Felt better today on a short trip..Ill have to take it out a little further and well see!

Driven it a bunch..No real improvement. Maybe a tad..

Any ideas on how/if a tranny can slip like that at high speeds? What are some other possible causes?

Ill probaly be taking it a shop on Monday for a diagnosis.

Since it happens at the same speed regardless of gear, it may be the VSS glitching, confusing the ECM...

Hmm..Is there any 'backyard' way to diagnose the VSS, or do you just swap it out?