tatersalad

Where on a TH350C transmission is the electricl plug that unlocks the torque converter? Is it on top of the bell housing where you can't see it?

Is the plug the same shape/size as the plug on the side of a 200-4R?

Thanks.

Aflac

TH350's dont have a lockup converter... take a peek at bowtieoverdrives.com . They have a really good FAQ about the 200r4 swap.

danno12345

I know my 81 has a TH350C with a lockup converter that I'm pretty sure ain't working.

I'd be interested in knowing where the plug is too also, since I'd like to put in a switch to make it work.

Dalannex

The 81' Corvette does have a lock up torque converter. It is a TH350C , a regular TH350 without the C is a non lockup converter. The plug is in roughly the same location as a 200 4R lockup plug, although on a 200 the plug is a little bit further back so the bell housing bolt that holds the harness needs to come out to gain some slack.


-Justin

Aflac

Thanks for clearing that up!

UKPaul

And it's really hard to see, let alone get to. As I remember, the connector points up. If you look at the firewall behind the d.s head you'll find a harness that goes down to this connector. The connector is the same type as the 200-4r uses so it can be installed on the 200-4r (pins will be used differently so wiring mods may be needed). Just be carefull not to break the locking tabs when removing the connector from the th350C (as I said, it's hard to get to ).

ruby76

The plug is on the drivers side on the "flat" (horizontal) par just above where the shifter lever is. It is a 4 prong plug, only two wires are used.

tatersalad

Did these start in 81? I was under the impression my 80 also has the locking TC but I can't find any wiring going to it. I have the LG4 engine CA only car.

ruby76

Now that's a tricky question. I think the TH350C I had came from (not much of a help) either 80 or 81 El Camino. Caprices etc had them also. I'm thinking it was a 1980 El Camino. I installed it on my 1968 chevy truck, It didn't have the computer stuff to operate it so I made a toggle switch under the dash. When I was on the Interstate I could flip the switch and save about 200-400 RPMs. Transmission was "smart" enough to only engage in third gear even if I left the toggle in ON position. But it would go directly from 1st to 3rd when it did

Mike Mercury

I also seem to remember that my 1980 had a lockup TC

Mike Mercury

according to this page, 1980 was the first year:

http://www.uwm.edu/People/ajthunes/index80.html

Ric80

According to an article in the April 2005 issue of Corvette Fever, the TH350C first appeared on late 1980 models and used engine vacuum to control lockup. So if you have an 80, you may or may not have the 350C.

I'm trying to figure out how to determine if mine has it or not. I'm guessing that since it used engine vacuum, there should be a vacuum line running to it and not the electrical connector thats on the 2004R??

tatersalad

I guess then in either case I'll need to get the brake pedal switch and wiring. BTO can probably clear it up. I was planning on getting the new shifter hardware from them anyway.

Thanks for the info.

Tater

migraine99

Be advised the the TH350 and TH350C have different internals. I found this out the hard way when I bought the wrong shift kit! For the 350C it's the B&M Transpak not Shift Improver Kit. DOH! :o

ruby76

The vacuum controled lock up was on/near the engine, no vacuum line went to the transmission other than the normal vacuum going to the modulator. Bottom line, if you have a 4 prong electrical plug on driverside of transmission, you have a TH350C. Apply 12 volts to it and it will lock up.

Ric80

Thanks for the clarification. Just one more question: What does the other end of the wire on the 4 prong plug connect to? Normally it would connect to the computer, but since there isnt one on the 80...

tatersalad

usually a 12 volt power source switched by the brake pedal....step on the brake, interrupt the power, and the convert unlocks. I've read some people use a switch mounted somewhere, but I think the brake pedal switch is the most common.

ruby76

I used a toggle switch to 12V mounted on the bottom edge of the dash to turn on the lock up converter.

Dalannex

My wife's 80 has a lockup converter TH350. The power goes through the brake switch to a relay, power through the relay to the vacuum switch mounted by the brake booster, then to the trans. Essentially the same setup as the BTO only with the addition of the vacuum switch.


-Justin

redwingvette

"Thanks for the clarification. Just one more question: What does the other end of the wire on the 4 prong plug connect to? Normally it would connect to the computer, but since there isnt one on the 80..."

I wired mine thruogh the brake switch that I got from BTO. I then installed a toggle switch to use so that I can turnit off if I am driving around town. The way it works without the toggle switch is that it will lock anytime the trans is in 4th (OD). so what happens if you are not driving above 40mph the engine starts to chug, especially if the guy in front of you is going slower then you are. By adding the switch in line with the brake switch the circut still is broken as soon as you put the brake on. However, the minute you release the brake the convertor locks up again. 200-4R Trans Install