TH350-C transmission, opinions please. - The 1947 - Present Chevrolet & GMC Truck Message Board Network

trendkill · 09-17-2009, 10:07 PM

I found out today that I have a TH350-C transmission. I know that they have a lockup torque converter. Can I get some opinions on this type of transmission so that I can decide what do about the one I have. Thanks.

**Boog** · 09-17-2009, 10:40 PM

With the lockup converter it is almost like an overdrive tranny in that it reduces the engine rpm when locked up thereby increasing fuel mileage. This tranny requires the electric/vacumn solenoid and brake lamp switch to make the lockup feature work correctly. However some guys take a cheaper route and wire in a toggle switch to manually lock/unlock the converter. You must remember to unlock it every time you come to a stop or it can kill the engine.
A local tranny shop told me I shouldn't run that trans without the lockup hooked up and working as it will kill the trans in short order. Could be a liability thing. It is in my truck but has not been on the road yet. Palf70step has one in his truck. Maybe he can answer some of your ?s

**Palf70Step** · 09-17-2009, 10:45 PM

Like Boog, mine is not yet on the road. I was told by my tranny guy you could run them without the lock up option, but you would have more slippage off the line, like a hi stall converter, but without the power. Yes it will kill it eventually and before it' time, but I have know a few folks to drive them for years without the lockup connected.

MY $.02, if you have the choice go with a 2004R for the overdrive, or just use the normal T350. It will be a bit stouter unit. Had mine not already been rebuilt, I would have used the T350 I recently acquired instead.

**Boog** · 09-17-2009, 10:56 PM

Oh hey Bill. I knew you were right around the corner.

I have that tranny in mine only for initial startup and moving around the shop and yard. I have a regular T350 to build and put in later.

trendkill · 09-17-2009, 11:07 PM

Thanks fellas. I'm not sure if the guy before me had it hooked up.I would really like to go with a th350. I probably will. Then it becomes pick and choose with some other stuff for my truck.

Tx Firefighter · 09-18-2009, 06:23 AM

I was broke one time and needed a trans so I bought a used TH350C from a junkyard. Obviously, it was used when I got it and I ran it 4 years without ever hooking up the lockup. I put about 75k miles on it like that. I never saw any signs I was hurting it in that time by running it unhooked.

09-17-2009, 10:07 PM	#1
trendkill Registered User Join Date: Jul 2009 Location: Ft. Worth, Tx 76135 Posts: 64	TH350-C transmission, opinions please. I found out today that I have a TH350-C transmission. I know that they have a lockup torque converter. Can I get some opinions on this type of transmission so that I can decide what do about the one I have. Thanks.

09-17-2009, 10:40 PM	#2
Boog laying low Join Date: Mar 2001 Location: Searcy, Ark. USA Posts: 13,514	Re: TH350-C transmission, opinions please. With the lockup converter it is almost like an overdrive tranny in that it reduces the engine rpm when locked up thereby increasing fuel mileage. This tranny requires the electric/vacumn solenoid and brake lamp switch to make the lockup feature work correctly. However some guys take a cheaper route and wire in a toggle switch to manually lock/unlock the converter. You must remember to unlock it every time you come to a stop or it can kill the engine. A local tranny shop told me I shouldn't run that trans without the lockup hooked up and working as it will kill the trans in short order. Could be a liability thing. It is in my truck but has not been on the road yet. Palf70step has one in his truck. Maybe he can answer some of your ?s __________________ Boog 69 Chevy stepside, 358/T350, 4.11 posi, 4.5/4 drop, rallys, poboy driver primer is finer 91 Chevy sportside, Tahoe, Yukon & GMC Crewcab All GM..'nuff said. I stand for the flag and kneel at the cross

09-17-2009, 10:45 PM	#3
Palf70Step State of Confusion! Join Date: Jul 2002 Location: Gulfport, MS USA Posts: 47,220	Re: TH350-C transmission, opinions please. Like Boog, mine is not yet on the road. I was told by my tranny guy you could run them without the lock up option, but you would have more slippage off the line, like a hi stall converter, but without the power. Yes it will kill it eventually and before it' time, but I have know a few folks to drive them for years without the lockup connected. MY $.02, if you have the choice go with a 2004R for the overdrive, or just use the normal T350. It will be a bit stouter unit. Had mine not already been rebuilt, I would have used the T350 I recently acquired instead. __________________ Bill 1970 Chevy Custom/10 LWB Fleetside 2010 Toyota Tacoma PreRunner SR5 Double Cab - DD Member of Louisiana Classic Truck Club (LCTC) Bill's Gallery Life isn't tied with a bow, but it's still a gift. Live simply. Love generously. Care deeply. Speak kindly. Leave the rest to God! Last edited by Palf70Step; 09-17-2009 at 10:45 PM.

09-17-2009, 10:56 PM	#4
Boog laying low Join Date: Mar 2001 Location: Searcy, Ark. USA Posts: 13,514	Re: TH350-C transmission, opinions please. Oh hey Bill. I knew you were right around the corner. I have that tranny in mine only for initial startup and moving around the shop and yard. I have a regular T350 to build and put in later. __________________ Boog 69 Chevy stepside, 358/T350, 4.11 posi, 4.5/4 drop, rallys, poboy driver primer is finer 91 Chevy sportside, Tahoe, Yukon & GMC Crewcab All GM..'nuff said. I stand for the flag and kneel at the cross

09-17-2009, 11:07 PM	#5
trendkill Registered User Join Date: Jul 2009 Location: Ft. Worth, Tx 76135 Posts: 64	Re: TH350-C transmission, opinions please. Thanks fellas. I'm not sure if the guy before me had it hooked up.I would really like to go with a th350. I probably will. Then it becomes pick and choose with some other stuff for my truck.

09-18-2009, 06:23 AM	#6
Tx Firefighter Watch out for your cornhole ! Join Date: Jun 2003 Location: Azle, Texas Posts: 14,162	Re: TH350-C transmission, opinions please. I was broke one time and needed a trans so I bought a used TH350C from a junkyard. Obviously, it was used when I got it and I ran it 4 years without ever hooking up the lockup. I put about 75k miles on it like that. I never saw any signs I was hurting it in that time by running it unhooked. __________________ I'm on the Instagram- @Gearhead_Kevin



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