I have a 1980 coupe with TH350 automatic transmission and had my transmission rebuilt. I also had a shift kit put in it. I also bought a new lockup torque converter on the advice of a friend. He said if I was rebuilding the transmission go a head a buy a new converter too.

I also had to replace the transmission torque switch that is on the firewall. So I know that is good.

It works great when I just give it gas and go, but if I have to slow down around the speeds where it needs to shift up or down, sometimes it shutters when it shifts in to the next gear.

It sometimes shifts hard too, but the guy who rebuilt it said that is normal for the shift kit he put in.

I called him back and told him about the shuttering and he said welcome to torque converter lockups. It never shuttered before I had the transmission rebuilt.

Is this true or is he full of crap.

Please help.

 

He is full of crap. Given the information that you've supplied here, there is no reason to believe that the fellow that did the work actually possesses the skills needed. Thus taking it back to him is extremely unlikely to result in a remedy.

Get your money back and take it to someone that is known to be a capable tranny man. In the meantime, you really had better not drive the car.

 

Replacing the torque converter was good advice
The torque converter should unlock long before it gets to the point where it starts shuddering. Sounds like the trans guy is trying to weasel out of doing some warranty work, or he just doesn't know what he's doing.
He should either fix it, or you can have it fixed by a competent trans man and present him with the bill

 

Thanks for the advice.

I will take it back to him and see what he does about it.

Does anyone know why it shudders?

 

It is difficult to say for certain, it could be that . . .

- the dampener in the clutch is too light, thus allowing the assembly to bottom out
- the dampener could actually have a busted spring or two
- the clutch material could have failed, allowing metal-to-metal contact. If this is the case, a bunch of fiber will be found in the pan
- the surface that the clutch engages has a crappy finish, thus not allowing the clutch to bite down properly
- insufficient pressure is being applied to the clutch to pin it down

All but the last item are converter defects. That last item is possible, but very unlikely, which is to say that you almost certainly have a defective converter.

Keep in mind that the converter can only shudder when going into lock-up. If the clutch does not bite down properly upon engagement, it slips, then catches, then slips, etc, etc, which is the shuddering sensation.

 

Thank you very much.

I bought a refurbish torque converter from O'Reillys and maybe it was bad.

Is there a way to check it without having to take the tranny out again?

 

My thoughts at this point, in no particular order. Too early. No coffee yet - not good -

- Ah, crap. You supplied the converter? For your sake, with there being a warranty issue or two, it would have been better if the tranny guy had. That way, any malfunction would be his problem. Now, the waters are muddied.

- Ok, yes, there is a way to check the converter . . . but it involves cutting it open. I'll bet you aren't equipped to do that. Besides doing that would void the warranty! Sooooo, what you need to do is contact that manufacturer. They may have a thing or two that they will want you to do but, more likely, they will just want to exchange it for another.

- if the converter clutch face failed as I suggested before, all of the fiber from it has contaminated the tranny fluid. Thus it has traveled throughout the system and, of course, that means that your glorious valve body it chock full of that crap. This would explain the inconsistent shifts. So the weird shifts may not be the tranny rebuilder's fault.

Ok, bottom line here . . .

The whole thing needs to be looked at again by a capable tranny guy. He needs to diagnose what has gone wrong to cause the inconsistent shifting and the lock-up shuddering as both of these actions are absolutely problems not simply life with a shift kit and a lock-up converter.

Man, I'm only about 5% awake right now, I hope this made sense.

 

Did you find the problem? I"m having the same problem on my "81. Trans was worked on 2 years ago before I bought the car. Thanks for the info.