How do I know for sure if dad's 84 c10 has a th350 or 350c?

[benoit454]

Just as the title says...
How can I be sure whether or not the 350 trans. in the 84 c10 is a th350 non lockup or a 350?

Now I run a th350 in my monte, I have no clue on year and specs of it but I have NO electrical connections anywhere on it so I figure it's a th350.

The one in the 84 has a plugin on it right under the cooler lines, that means it's a 350c? I'd think so but not sure.

I wanna get a shift kit for it sometime and I know I've heard they are 2 different kits for a th350 and one for a 350c, so you have to know which it is for sure to get the right kit.

[krue]

If it's a 350c it will have a 4 pin electrical plug on the drivers side, behind the shift linkage.

[Roper]

Originally Posted by krue

If it's a 350c it will have a 4 pin electrical plug on the drivers side, behind the shift linkage.

What is a 350c?
My transmission has a plug like that on the drivers side. The wires are cut off the plug. My truck is an 81. This transmission is a rebuilt one that I put in. I always thought it was a regular th350. It works perfectly.

[benoit454]

As far as I know it means it has a lockup torque convertor, that's hooked into a computer, electronic lockup.

[Roper]

Originally Posted by benoit454

As far as I know it means it has a lockup torque convertor, that's hooked into a computer, electronic lockup.

What does that mean?
Like I said before my tranny has the wires cut off but it works perfectly as far as I can tell. Example it shifts great and I have all three gears.

[Slonaker]

If it has the 4 pin plug, it has a lockup converter like the newer cars have, This means that once you get to cruise spedd, the conveerter no longer allows the slippage that it normally has. This slippage is what allows you to keep it in gear at a stop. Unfortunately, it wastes gas once you are at cruise speed.

Lockup converters "lock" once you stop accelerating so that one turn of the engine gets one turn of the transmission. It lowers your rpm a little, and saves gas.

A TH350C will work just fine without it being hooked up. I have seen people on here report that theirs have worked fin for years disconnected. Mine worked before I put my new engine in, but does not now. I left the switch on the engine that I thought controlled it, but it was the wrong one. Oops...

Slonaker

[krue]

Originally Posted by Roper

What does that mean?
Like I said before my tranny has the wires cut off but it works perfectly as far as I can tell. Example it shifts great and I have all three gears.

If you had the lockup convertor wired up and it worked right, the convertor would lock up at hiway speed, improving your gas mileage a little bit.

[Roper]

Thanks for explaining that.
Does a normal th350 not lock up the same as my unhooked 350c does?
Im wondering how much of a pain it would be for me to try to find a computer for my 350c. Example if I find a junked one somewhere can I just rob the plug/wires and computer off it and install it on mine? Does the 350c have its own little computer or does it run off the main brain box of a vehicle?
Do different vehicles that have a 350c have different computers running them?
Roughly how much gas mileage are we talking about here between a non lock up tranny and a lock up one?
Thanks
I sure learn a lot of stuff from this forum. Appreciate you guys.

[benoit454]

I don't think you'd pickup more then maybe 5 mpg at best, probably more like 1-3 or so.

I'd think your unhooked 350c would work and act exactly like a normal th350 as it has slippage.

I read this huge article once explaining all of it, a normal non lockup tc never locks up 100 percent it's always at say 90, and ONLY by the use of the electronic lockup can it be at 100 percent.

As for lockup I know for 700r4's and other lockups they have aftermarket kits to buy from say b&m or tci and painless I think, lockup kits to control your lockup tc without having the factory computer.




Now back to my topic....

You guys say if it's a lockup the plugin in by the gear shift lever/trans arm, like a 700r4. I've seen thoose and the truck has that plugin but it's hanging loose, I don't know if the transmission has it or not. I know the truck does because I've seen the plugin in the wiring harness hanging underneath.


Question is what the heck plugs in under the cooler lines????????

I never seen something plugin under the lines before. Anyone know what it is or does?

[Slonaker]

Originally Posted by Roper

Thanks for explaining that.
Does a normal th350 not lock up the same as my unhooked 350c does?
Im wondering how much of a pain it would be for me to try to find a computer for my 350c. Example if I find a junked one somewhere can I just rob the plug/wires and computer off it and install it on mine? Does the 350c have its own little computer or does it run off the main brain box of a vehicle?
Do different vehicles that have a 350c have different computers running them?
Roughly how much gas mileage are we talking about here between a non lock up tranny and a lock up one?
Thanks
I sure learn a lot of stuff from this forum. Appreciate you guys.

A regular TH350 does not lock up. Neither does your TH350C as long as you have it disconnected.

An '84 C10 is not computer controlled. I suspect that the converter is controlled by a vacuum switch, and maybe the kickdown cable, but I really don't know. I know there is some more info on it in the FAQ section here, but I don't have a link handy.

I don't know how much gas mileage is to be gained, but mine is so poor that I bet it is worth hooking it back up.

Originally Posted by benoit454

Now back to my topic....

Question is what the heck plugs in under the cooler lines????????

I never seen something plugin under the lines before. Anyone know what it is or does?

I would guess backup lights, but it is only a guess.

Slonaker

[krue]

Look in the Index link in my sig, there's a diagram for the lockup wiring, it uses a vacuum switch and a brake pedal switch iirc.

[benoit454]

Well guys there's no plugin behind or around the shifter linkage/arm on that side at all.

I guess that would mean it's not a 350c?

it has a vacuum modulator same size and place as a th350 I have, and has same size pan as my th350.


That plugin under the oil cooler lines for it is like a 2 prong oil pressure sender or switch that you'd find in back of the block. Sorta small and thin going into the trans, then comes out to a big bulbed head with a 2 wire plugin, plugged into it. I have no idea what it is, has me lost completely.

Everything I see listed for 80 and up 350 is a lockup, and the trucks an 84 and all original as far as I know.

Would it help if I got pics?

[Slonaker]

The pan and modulator, on my TH350C look just like the ones on my TH350 in the coupe AFAIK. I doubt the truck was available with a regular TH350, but one could have been transplanted.

The plug is on the driver's side, I think. It is square, and I believe it faces upward. It might not be obvious if you have not seen one before. It looks like this one on a 700R4.

http://www.iotech.no/corvette/techni...kup_socket.jpg

Slonaker

[benoit454]

Yea I've seen them before because the 86 we had, it had a 700r4 and was unplugged. I found the plug and the plugin and hooked it up.

On this 84 there is no plug at all on the driver's side. I felt and dug around for 5 or 10 minutes because I knew it was on the DS and behind the shifter hookup.

No where to be found. it might be completely clogged with dirt and grease but it didn't even feel like there was a spot for it. I seriously doubt there's a plug on it anywheres.

That one on the PS, just throws me off, never sen it before on any of them. But I haven't seen many transmissions either.

[bigtruck81]

Originally Posted by benoit454

As far as I know it means it has a lockup torque convertor, that's hooked into a computer, electronic lockup.

no, its not. its hooked up to 12v and a vacuum switch, and the brake light switch.

[benoit454]

Well anyways guys here's pics of that plugin on the passenger side, anyone know what it is? I know it's not a lockup transmission because there's no plugin at all on the driver's side.

I just wonder what this little wonderful device is rigged up on there lol







Most th350's I've seen have all been like this one, with no plugin at all over there....



I guess that circled area where that plug is or whatever is where this plugin thing is at on the one in the 84.

[lurch115]

i would also like to know what that plug on the passanger side is for as my '84 with a 350c also has that same plug

[benoit454]

So you have an 84 also and yours has a 350c in it?

Does it have the 4 pin plugin on the driver's side as they mentioned? I know mine doesn't but I wonder what the heck that is on the side and what it does.

[lurch115]

yeah, mine has the 4 pinner on the driverside.... one good thing about having a truck that is all original...it still has the correct stuff in it...well for now...its getting the 355 out of my pulling truck and hopefully a 700r4 which should work great since the plug is already there....i think i'd do some diggin' tonight and see what i can find about that other deal on the passagerside though

[benoit454]

good lcuk and be sure to let me know what you come up with.

Mines been changed then I figure because I thought it to be all original it was claimed to have been but with no plugin on the transmission something tells me it's been changed. I have no idea what, how, or why the one on the passenger side was saved and hooked up though.

[lurch115]

okay, here is the closest thing i could come up with since Haynes Manuals don't have crap for automatic transmissions in them.....that solenoid is part of the TCS system(transmission controlled spark).... basically what that solenoid does send a signal to another electronic solenoid when the transmission is operating in low forward gears. Which in turn allows the other solenoid to vent all vacuum pressure that would normally go to the vacuum advance out into the engine compartment.......so basically that solenoid is what helps to eliminate the vacuum advance from operating in normal in town driving....(35mph or under) make sence??? keep in mind...this was the only thing i could find that it could be.... i might stop by the Chevy dealer tomarrow on my way home and see if they can tell me what it is for sure....but i think what i put above is what it is for....



sorry for the long post...

[benoit454]

Actually I was going to say the same thing. I found that trans. spark controller in my lmc book listed for 76 only but it looked just like the thing in the side of the trans. in the 84.

So that was my best guess too that it's a tsc and that's all I knew, didn't know what it did or anything.

[lurch115]

well now we both know what the heck it is and what it does....and i can tell you another thing....thats one thing i'll be making sure to "accidentally" forget to hook back up when i put the motor outta my pullin' truck in mine.... cause i want full vacuum advance everytime i mash the pedal through the radiator... that motor is crankin' about 400hp and i want it on demand at all times... never know when a ford might pull up beside me....

[benoit454]

Honestly me too, give me the old carb's mech choke, vac. sec. or mech sec. and no computer controlled sensor distributor or anywhere else for that matter.