TH350 electrical connectors?

[Burmanater]

So a while back I nuked the second and third gears in my 84 c10. Now I'm assuming since all the plugs were there and plugged in that this is the original trans to my truck.

My question is why does a TH350 have a 4 pin connector like a 700r4 on the back above the pan on the drivers side and what is the 2 prong connector up on the passenger side towards the top just behind where the bellhousing ends?

I've never worked on anything besides this that had a TH350 with any kind of electrical wiring to it. The one I'm replacing it with doesn't have any either.

Thanks for any info, really just curious as to why they are there. Doesn't mention either of them in my Haynes manual either.

[donut]

Taking a guess here, but could it be a thm 350-c with the lock up converter? Think pre 700-r4. I'm sure more knowledgeable folks will chime in later.

[GRADYS Performance]

TH350 transmissions were built until 1979. TH350C transmissions were built 1980-86. The TH350C transmissions have a lock up torque converter. That is what the square 4 prong plug is for in the middle of the case. The front electrical connection is for smog equipment or lockup to tell the engine what gear the trans is in. TH350 transmissions and converters have to be kept together, TH350C transmissions and converters have to be kept together. The lockup and non lockup will not interchange between the two. They will both bolt into any vehicle the same as as the mounting items are the same. But you would have to deal with the lockup/non lockup issues if you were to make that kind of swap.

[Slammed84]

Originally Posted by GRADYS Performance

TH350 transmissions were built until 1979. TH350C transmissions were built 1980-86. The TH350C transmissions have a lock up torque converter. That is what the square 4 prong plug is for in the middle of the case. The front electrical connection is for smog equipment or lockup to tell the engine what gear the trans is in. TH350 transmissions and converters have to be kept together, TH350C transmissions and converters have to be kept together. The lockup and non lockup will not interchange between the two. They will both bolt into any vehicle the same as as the mounting items are the same. But you would have to deal with the lockup/non lockup issues if you were to make that kind of swap.

So you're saying that if one was to come across a TH350 that has an electrical plug on it that you would be forced to use a lockup converter?
That sucks! I got a TH350 in my garage sitting around waiting for a home someday, but im not sure if it has the plug or not.....

[GRADYS Performance]

Originally Posted by Slammed84

So you're saying that if one was to come across a TH350 that has an electrical plug on it that you would be forced to use a lockup converter?
That sucks! I got a TH350 in my garage sitting around waiting for a home someday, but im not sure if it has the plug or not.....

If it has the square 4 prong connector in the middle of the case it is a TH350C. And has to be used with a lock up converter and the electrical system to work the lockup properly.

[Burmanater]

I got a converter with the trans I bought so I planned on using that. I always keep converters with the trans they came with. I would actually prefer not to have the lockup style converter.

[Scott91370]

Originally Posted by GRADYS Performance

TH350 transmissions were built until 1979. TH350C transmissions were built 1980-86. The TH350C transmissions have a lock up torque converter. That is what the square 4 prong plug is for in the middle of the case. The front electrical connection is for smog equipment or lockup to tell the engine what gear the trans is in.

Hoping @GRADYS Performance still comes around and is still subscribed to this thread...

Along with the round 2 pin black plug (passenger's side) and the square 4 pin white plug (driver's side) there is a rectangular 2 pin red connector that is supposed to connect to a two port vacuum source. Do you know where this source is located?

[hatzie]

The TCC vacuum source is ported vacuum above the throttle plates on the carburetor.
It runs from that ported vacuum to the thermo vacuum switch on the water neck.
From there it runs to the purge valve on the charcoal emissions vapor can and wyes through a vacuum delay can to the TCC vacuum switch.

[Scott91370]

Thanks hatzie!!

[GRADYS Performance]

Thanks Hatzie, I am familiar with the transmission parts but not as knowledgeable about the different wiring combinations depending on the vehicle it is installed in.