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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: doctrdoo on December 31, 2006, 05:09:00 pm

Title: TH350 trans question??
Post by: doctrdoo on December 31, 2006, 05:09:00 pm: i have a TH350 transmission in my 85 C10 p/u with a 350 eng. when i pulled the trans pan off to change the trans filter- i noticed that there are some wires going to what looks like a solenoid on the valve body.what are these wires for? any help would be great.
Title: Re: TH350 trans question??
Post by: Lt.Del on January 01, 2007, 12:39:00 am: any pics.

I may be wrong, but the only voltage would go to a th350c, lock up converter. Do you have a plug on the drivers side of the body of the trans with wires?
SgtDel
aka "Andy"

www.delbridge.net

1979 Big 10 383 stroker
1991 Blu 'Burb 3/4 ton 4x4
Title: Re: TH350 trans question??
Post by: doctrdoo on January 01, 2007, 10:36:00 am: yes,there is a plug on the body of the trans and some wires leading into the main wire harness but i dont know where the wires go after they mix with the rest of the wires.there are alot of wires and plugs in the eng.bay that dont go to anything. right now i have just the basic wires(distributor,alt.starter) hooked up since the eng. was replaced before i got the truck.will it hurt the trans if this lockup converter is not hooked up? i dont think it's been hooked up since i got the truck and has been running ok.sorry about not having pics.any suggestions?
Title: Re: TH350 trans question??
Post by: DnStClr on January 01, 2007, 04:44:00 pm: On the side of your tranny, there's a small tag, probably covered with grime, that says either TH350 or TH350C. Sgt. Dell is right. The wiring connectot signals a lockup system. The connector and wires lead to a vaccum switch that locks up the torque converter when the engine speed reaches a certain rpm. The 12 volts excites the solenoid and closes the switch. It only gets 12volts when the key switch is on.
It was probably disconnected because the converter, when locked, creates heat when the clutches are locked, which destroys a tranny. So a lot of guys found out they could increase the life of the tranny by keeping it unlocked,and disconnected the wiring connector, although their fuel mileage decreased because that's one of the big benefits of a locked torque converter- it increases fuel mileage at highway speeds.
The thing is- a TH350C (lockup version)- also uses a different distributor than a TH350 tranny.So the engine was tuned differently.
My 2 cents worth anyway.
Don St.Clair
Culleoka Tn
Title: Re: TH350 trans question??
Post by: VileZambonie on January 01, 2007, 05:22:00 pm: Locking the converter actually decreases the heat tremendously and unplugging it could cause the fluid to overheat and aerate. The TCC solenoid is actauted by a pressure switch. The low Vac switch unlocks the converter when maifold pressure drops (when you open the throttle) for quick throttle response and torque multiplication. If you are going to do it right make sure you hook the lock up converter again. Usually if someone has unplugged it, it's because they may have had a problem with the solenoid sticking therefore the converter will not unlock.
Title: Re: TH350 trans question??
Post by: doctrdoo on January 01, 2007, 05:26:00 pm: what do you mean "a different distributor"? are you talking about the distributor on the motor? i know that the distributor on the motor is one that has an ecm attached to it but i disconnected that.
Title: Re: TH350 trans question??
Post by: DnStClr on January 01, 2007, 05:32:00 pm: Yes. The engine distributor.
Don St.Clair
Culleoka Tn
Title: Re: TH350 trans question??
Post by: Lt.Del on January 01, 2007, 07:41:00 pm: When i replaced my engine to a 383 I got a th350c tranny. I didn't know it at the time, but i used it anyway. Since my ole 79 didn't have any of the switches that control the lock up, like brake switch, distr switch, vacuum switch, I simply brought a 12 volt hot wire to the plug on the tranny. I hooked up a switch to it which i control at my dash. When in 3rd gear and steady atleast 40mph, i flip the switch and lock up the converter.

It works pretty well that way.
SgtDel
aka "Andy"

www.delbridge.net

1979 Big 10 383 stroker
1991 Blu 'Burb 3/4 ton 4x4
Edited by: SgtDel at: 1/1/07 7:42 pm
Title: TH350 trans question
Post by: doctrdoo on January 08, 2007, 06:01:00 pm: if i decided to put a TH350 trans instead of a TH350C trans in my truck-is there any differences i should know about other than the converter being a lockup converter?