TH350C questions.

[82355]

I have a TH350C I pulled out of a 1980 GMC K5 I am cutting up. I was thinking about using it in a 1975 K5 I have (haven't been able to find any SM465/NP208 combos....). Anyone mess with these? How does the lockup work? I see there is a two wire weatherpack connector on the left rear of the case. I assume put 12v+ and ground to it, and the converter locks up? I also would assume, like a TH700R4, that it will not lock up in 1st? Let me know what you know, thanks.

Martin

 

[diesel4me]

My 81 G10 van has that TH350C (or MV4) tranny,it uses a vacuum switch to operate the TCC in tandem with the brake stoplight switch...I suppose you could rig the wires to a toggle switch ,but its easy enough to rob the switches off a boneyard docor along with the oem wiring to make it work as intended..I dont know if the TCC would lock up in first or second gear or not...

When I first bought my van the brake light switch wasn't adjusted right,so it never let the converter lock up...took it 80 miles to my brothers house and by the time I got there you could feel how hot the tranny was...we noticed the brake lights were staying on constantly,so we adjusted the switch and it was much better on the way home!..also got better gas mileage too...

 

[82355]

Did some reading, torque converter clutch is fed oil from the direct clutch, so it only allows lockup in 3rd gear. That being said, you can modify the case so that is will apply in all three gears.

Martin

 

[Greg Ducato]

You don't need to hook up lockup if you don't want to. The outside wire on the plug should be for 12 volts, the trans probably uses a governor switch inside to ground that is pre calibrated to lockup around the same MPH as the number embossed on the switch. Most factory switches are 39-42

 

[79rustyk10]

I thought they got the lockup in 81 or 82. The few 1980 trucks I've seen have a regular th350. I could be wrong though too, never know what's been swapped in the last 30 plus years.

 

[82355]

You don't need to hook up lockup if you don't want to. The outside wire on the plug should be for 12 volts, the trans probably uses a governor switch inside to ground that is pre calibrated to lockup around the same MPH as the number embossed on the switch. Most factory switches are 39-42

There are two terminals in the connector though. Why would you not want to use the lockup? Should help keep the tranny cool, and improve fuel economy.

My 1987 V10 has a 350 TBI, SM465/NP208, 3.42 gears, and 31x10.5x15" tires, it runs a few hundred RPM less down the highway than my 1988 GMC V1500 Suburban with its 350 TBI, TH400/NP241, 3.42 gears and 31x10.5x15" tires. It also feels much stronger with a much more tired engine. I can never understand why people like automatics????

Martin

 

[82355]

I thought they got the lockup in 81 or 82. The few 1980 trucks I've seen have a regular th350. I could be wrong though too, never know what's been swapped in the last 30 plus years.

It probably isn't original to the K5. There was no wire hooked up to the connector. I didn't even know it was a "C" till I had it out of the truck.

Martin

 

[dyeager535]

I can never understand why people like automatics????

Martin

Me either.

I would think with some pretty minor modifications to the '82-86 700R4 TCC lockup wiring , making that work with the TH350C shouldn't be that tough.

I agree, if you have lockup, and can run it, no reason not to as long as it doesn't take a ton of money and effort to do so.

 

[82355]

Bump. What would be the best way to use on of these without any of the parts from the donor vehicle besides the actual transmission?

Martin

 

[Greg Ducato]

Bump. What would be the best way to use on of these without any of the parts from the donor vehicle besides the actual transmission?

Martin

You mean the best way to use the 350 Lockup trans with lockup functioning in a non stock application?

 

[82355]

Correct.

Martin

 

[Greg Ducato]

If you can pull the pan and post or email me a picture of the internal harness/valve body (remove the filter please) I can give you the correct info to make this all work quite easily.

 

[82355]

Can do.

Martin

 

[82355]

Martin

 

[Greg Ducato]

Super easy, just run 12 volts to the case connector, the solenoid grounds through the governor switch that is on the valve body, you can delay the speed it locks up at by changing to a higher numeric governor switch.

 

[82355]

Wow, that is simple. Thanks.

Martin

 

[Cruz89K5]

Greg your knowledge newer ceases to amaze. We're lucky to have you around here.

 

[Greg Ducato]

Aw shucks, I'm the lucky one, there aren't too many places a fellow can hang out with a bunch of others so passionate about these old trucks. I take away a lot more from here than I give.