TH350C Lockup on 82 C10 - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Liberty · 03-26-2015, 05:09 PM

As it turns out my tranny lockup has never worked as the VAC lines going to the lockupswitches are missing. Does anyone know where the lines are supposed to go? There are two switches on my truck, one on the driver side and the other on the passenger.

Engine is a 350 with a QudraJet, Tranny is a 350C.

geezer#99 · 03-26-2015, 05:48 PM

Try this. It's for an 83 but might be close.
http://67-72chevytrucks.com/vboard/s...d.php?t=215546

Liberty · 03-26-2015, 06:17 PM

I've got the diagram still under the hood, but I'm a bit thrown off with there being two vac switches on the firewall. Only one has the delay valve still on it, and thats running to the switch on the drivers side by the brake booster.

Liberty · 03-26-2015, 07:17 PM

Theres two unhooked wiring harnesses on the passenger side of the tranny That I have no idea where they should go. It looks like the PO might have disabled the whole thing... I wonder why.

Ric's/86 · 03-26-2015, 07:41 PM

I'm no expert. The driver side is the lockup.
Maybe this can help you.

jetmech85 · 03-26-2015, 11:30 PM

Passenger side vac switch gives signal to ESC computer.

Liberty · 03-27-2015, 07:46 AM

Thank you guys for the help so far! Now before I jump in too deep, how useful are half of these vac lines? Almost none of my vac system operates anything, the only comfirmed working VAC systems in operation right now is The Dizzy, Cruise, tranny, and A/C ducting.

The vapor can has one line running to the carb, and one to the gas tank with all other ports plugged.
The stovepipe vac motor on the air filter housing is disconnected.
The torq converter until now has been disconnected, but I cannot confirm lockup yet.

Liberty · 03-27-2015, 07:59 AM

More importantly really, will reenabling any of this VAC equipment improve engine performance or gas mileage?

benscool1 · 03-27-2015, 08:32 AM

I'm having the same issue with my 84 with 700r4. When I swapped engines I removed all the vacuum lines except the dizzy and HVAC. I removed the line going to the lockup switch thinking it was part of the cruise system on my truck (which doesn't work anyway). I'm not sure how a th350 works but on a 700r4 when the lockup engages it is supposed to lower your rpms a bit giving you slightly better mileage and also cutting down on heat. It may be a pretty marginal improvement though. My understanding is that the majority of the other vacuum lines are related to the smog/emissions system.

What did you use for the vacuum source for your lock up switch? Did you hook it up like the diagram?

king-918 · 03-27-2015, 11:58 AM

Quote:

Originally Posted by Liberty

More importantly really, will reenabling any of this VAC equipment improve engine performance or gas mileage?

In theory yes, lockup stops slippage that all converters have but in truth the real question is does the lockup lock 100%. You should get a slight bump in mpg

GRADYS Performance · 03-30-2015, 03:52 PM

Quote:

Originally Posted by Liberty

Theres two unhooked wiring harnesses on the passenger side of the tranny That I have no idea where they should go. It looks like the PO might have disabled the whole thing... I wonder why.

Are you sure you have a TH350C transmission?

Liberty · 03-30-2015, 04:56 PM

It is without a doubt a 350C.

GRADYS Performance · 03-30-2015, 10:53 PM

The TH350C has a 4 prong square plastic electrical connector on the pass side of the case. Does your trans have this and is anything plugged into it?

Liberty · 03-31-2015, 06:16 AM

Quote:

Originally Posted by GRADYS Performance

The TH350C has a 4 prong square plastic electrical connector on the pass side of the case. Does your trans have this and is anything plugged into it?

I'll check that today, it has the two prong on the driver side which is hooked up, and there is a disconnected 4 prong harness on the pass side.

Hopefully I can get under there before the rain! Now is the hookup towards the front or back of the tranny?

Edit: One more thing! I have no neutral safety switch, it was bypassed awhile back. I'm not sure how important that is to any of this but I figured I'd let it be known.

GRADYS Performance · 03-31-2015, 02:43 PM

Quote:

Originally Posted by GRADYS Performance

The TH350C has a 4 prong square plastic electrical connector on the pass side of the case. Does your trans have this and is anything plugged into it?

I looked at a case today, it is on the drivers side about half way back the pan going down into the case from the top.

Liberty · 03-31-2015, 04:36 PM

Ok I got some pictures of what I have.

Theres a two prong connector on the driver side, on the pass side theres an unused sqaurish one and round one.

Liberty · 03-31-2015, 04:37 PM

Heres the connectors.

Liberty · 03-31-2015, 04:38 PM

Another angle

GRADYS Performance · 03-31-2015, 05:01 PM

It is a TH350C.

03-26-2015, 05:09 PM	#1
Liberty Registered User Join Date: Feb 2015 Location: Bonham, Texas Posts: 241	TH350C Lockup on 82 C10 As it turns out my tranny lockup has never worked as the VAC lines going to the lockupswitches are missing. Does anyone know where the lines are supposed to go? There are two switches on my truck, one on the driver side and the other on the passenger. Engine is a 350 with a QudraJet, Tranny is a 350C.

03-26-2015, 05:48 PM	#2
geezer#99 Registered User Join Date: Aug 2009 Location: Bowser Posts: 13,736	Re: TH350C Lockup on 82 C10 Try this. It's for an 83 but might be close. http://67-72chevytrucks.com/vboard/s...d.php?t=215546

03-26-2015, 06:17 PM	#3
Liberty Registered User Join Date: Feb 2015 Location: Bonham, Texas Posts: 241	Re: TH350C Lockup on 82 C10 I've got the diagram still under the hood, but I'm a bit thrown off with there being two vac switches on the firewall. Only one has the delay valve still on it, and thats running to the switch on the drivers side by the brake booster. Attached Images

03-26-2015, 07:17 PM	#4
Liberty Registered User Join Date: Feb 2015 Location: Bonham, Texas Posts: 241	Re: TH350C Lockup on 82 C10 Theres two unhooked wiring harnesses on the passenger side of the tranny That I have no idea where they should go. It looks like the PO might have disabled the whole thing... I wonder why.

03-26-2015, 07:41 PM	#5
Ric's/86 Registered User Join Date: Dec 2013 Location: Ocala Fl Posts: 37	Re: TH350C Lockup on 82 C10 I'm no expert. The driver side is the lockup. Maybe this can help you. Attached Images

03-26-2015, 11:30 PM	#6
jetmech85 Registered User Join Date: Sep 2014 Location: Texas Posts: 215	Re: TH350C Lockup on 82 C10 Passenger side vac switch gives signal to ESC computer.

03-27-2015, 07:46 AM	#7
Liberty Registered User Join Date: Feb 2015 Location: Bonham, Texas Posts: 241	Re: TH350C Lockup on 82 C10 Thank you guys for the help so far! Now before I jump in too deep, how useful are half of these vac lines? Almost none of my vac system operates anything, the only comfirmed working VAC systems in operation right now is The Dizzy, Cruise, tranny, and A/C ducting. The vapor can has one line running to the carb, and one to the gas tank with all other ports plugged. The stovepipe vac motor on the air filter housing is disconnected. The torq converter until now has been disconnected, but I cannot confirm lockup yet.

03-27-2015, 07:59 AM	#8
Liberty Registered User Join Date: Feb 2015 Location: Bonham, Texas Posts: 241	Re: TH350C Lockup on 82 C10 More importantly really, will reenabling any of this VAC equipment improve engine performance or gas mileage?

03-27-2015, 08:32 AM	#9
benscool1 Registered User Join Date: Mar 2003 Location: Williamsfield, IL Posts: 781	Re: TH350C Lockup on 82 C10 I'm having the same issue with my 84 with 700r4. When I swapped engines I removed all the vacuum lines except the dizzy and HVAC. I removed the line going to the lockup switch thinking it was part of the cruise system on my truck (which doesn't work anyway). I'm not sure how a th350 works but on a 700r4 when the lockup engages it is supposed to lower your rpms a bit giving you slightly better mileage and also cutting down on heat. It may be a pretty marginal improvement though. My understanding is that the majority of the other vacuum lines are related to the smog/emissions system. What did you use for the vacuum source for your lock up switch? Did you hook it up like the diagram? __________________ Ben 84 C10 Silverado 14 Silverado Z71 Last edited by benscool1; 03-27-2015 at 08:45 AM.

03-30-2015, 04:56 PM	#12
Liberty Registered User Join Date: Feb 2015 Location: Bonham, Texas Posts: 241	Re: TH350C Lockup on 82 C10 It is without a doubt a 350C.

03-30-2015, 10:53 PM	#13
GRADYS Performance Registered User Join Date: Dec 2013 Location: Columbus, Oh Posts: 367	Re: TH350C Lockup on 82 C10 The TH350C has a 4 prong square plastic electrical connector on the pass side of the case. Does your trans have this and is anything plugged into it?

03-31-2015, 04:36 PM	#16
Liberty Registered User Join Date: Feb 2015 Location: Bonham, Texas Posts: 241	Re: TH350C Lockup on 82 C10 Ok I got some pictures of what I have. Theres a two prong connector on the driver side, on the pass side theres an unused sqaurish one and round one. Attached Images

03-31-2015, 04:37 PM	#17
Liberty Registered User Join Date: Feb 2015 Location: Bonham, Texas Posts: 241	Re: TH350C Lockup on 82 C10 Heres the connectors. Attached Images

03-31-2015, 04:38 PM	#18
Liberty Registered User Join Date: Feb 2015 Location: Bonham, Texas Posts: 241	Re: TH350C Lockup on 82 C10 Another angle Attached Images

03-31-2015, 05:01 PM	#19
GRADYS Performance Registered User Join Date: Dec 2013 Location: Columbus, Oh Posts: 367	Re: TH350C Lockup on 82 C10 It is a TH350C.



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