Early TCC lockup

[pshimek]

1980 Pontiac Grand Lemans 3.8L 200C Xmission RWD Stock

Torque converter locks up at about 32 MPH, fairly quickly after shift to 3rd, with stop light to stop light type driving, too early, and causes some engine lug. I checked and adjusted per manual the TV cable, which seems to be working properly. I understand there is no computer control of the TCC. I am guessing there is a brake switch to disable TCC lockup, and a vacuum switch to enable. I do not remember any pressure switch on the valve body when I last changed the filter. I havent had the car too long, but it had this problem when I got it.
If there is a vacuum switch, where would it be located or in what circuit, and if not, what controls TCC lockup, and what components are involved. Is there such a thing as a TCC circuit diagram for this model ?

Thanks for your help!

 

[mikestertwo]

I'm not familiar with the 200C but I think the lockup is controlled by a shuttle valve in the valve body like the early non-computer controlled 200-4R transmissions. I'm sure someone will jump in here who knows more.

 

[SSedan64]

1980 Pontiac Grand Lemans 3.8L 200C Xmission RWD Stock

Torque converter locks up at about 32 MPH, fairly quickly after shift to 3rd, with stop light to stop light type driving, too early, and causes some engine lug. I checked and adjusted per manual the TV cable, which seems to be working properly. I understand there is no computer control of the TCC. I am guessing there is a brake switch to disable TCC lockup, and a vacuum switch to enable. I do not remember any pressure switch on the valve body when I last changed the filter. I havent had the car too long, but it had this problem when I got it.
If there is a vacuum switch, where would it be located or in what circuit, and if not, what controls TCC lockup, and what components are involved. Is there such a thing as a TCC circuit diagram for this model ?

Thanks for your help!

According to my GM 200C book there's a normally open governor oil pressure switch that provides a ground to the lockup solenoid inside the trans next to the valve body on left side towards the rear. I'm not sure if yours has a vacuum switch, but probably does. My 1980 C10 with a TH350C and has a vacuum switch on the intake manifold. If yours has a vacuum switch you can get an adjustable V/switch on Ebay to set the lockup speed. Or get one of these>
eBay Motors: B&M #70244 GM200R4/700R4 CONVERTER LOCK UP CONTROL NEW (item 160261247069 end time Jul-20-08 17:51:32 PDT)

 

[pshimek]

Never thought about it, but I looked at the emissions vacuum diagram under the hood yesterday evening, and it shows a converter switch with a vacuum delay in line. Found it mounted to the driver side fender. (Wondered what it was for). The disphragm in the switch is probably not like it should be because of age, and is causing a shift in switching. Is the adjustable vacuum switch available at an auto parts ? I think adjustable V/switch would be the route to go to solve my shifting problem.

Thanks a lot for your help!