TH200C - Where is the lockup switch?

[Michael Bennett]

Just put a 400 small block in my 1980 malibu in place of the 229 six. I know the TH200C won't be long for this world but I'd like to make it last until I can get a TH350 ready to go in. Since this doesn't have a computer, I think vacuum is supposed to control converter lock up? The only thing like that I see is a vacuum switch on the driver's fender but the vacuum lines were connected to the old carb and the charcoal canister. I'm bypassing the canister so do I just hook the switch up to manifold vacuum? ported?

 

[Michael Bennett]

Just realized I probably should have posted this in the drivetrain section.

 

[Wageslave]

For durability purposes, you maybe better off leaving the lock-up converter unplugged. If you mash the gas while the lock-up converter is engaged, the full power of the engine will go to the internals of the transmission. If the converter is unlocked, the torque converter will take some of the strain.

You will only lose about 100 RPM at cruise speeds with it unhooked, but the trade off is a little more heat from the converter. Unless you are brake torquing it though, there shouldn't be enough to be a concern.

I have been running one behind a healthy 350 with good results.

That being said, if you do want to hook it up it should be plumbed as follows: Manifold vacuum source -> one way check valve -> vacuum switch.

 

[Michael Bennett]

For durability purposes, you maybe better off leaving the lock-up converter unplugged. If you mash the gas while the lock-up converter is engaged, the full power of the engine will go to the internals of the transmission. If the converter is unlocked, the torque converter will take some of the strain.

You will only lose about 100 RPM at cruise speeds with it unhooked, but the trade off is a little more heat from the converter. Unless you are brake torquing it though, there shouldn't be enough to be a concern.

I have been running one behind a healthy 350 with good results.

That being said, if you do want to hook it up it should be plumbed as follows: Manifold vacuum source -> one way check valve -> vacuum switch.

Okay so maybe I'll just leave it unhooked and get a transmission cooler.

 

[Ribbedroof]

From the 1980 GM shop manual