Question on th 350 tranny - The 1947 - Present Chevrolet & GMC Truck Message Board Network

stick · 03-03-2005, 04:35 PM

I'm a new member and have a friend that just bought a th 350 tranny with a lockup converter out of an '80 Chevrolet half-ton. He has put it in a '55 Nomad with a new small block GM crate engine. Two questions. I'm assuming, in calculating which speedo gear he needs, that the th 350 has an 8 tooth drive (not driven) gear. I think the truck was a two wheel drive. Is that correct?

Also, there is a single green wire coming out of the transmission which we are assuming is the on/off for the converter but we don't have a clue as to how to run the wire. Any ideas on that?

*1FaastC10* · 03-03-2005, 05:02 PM

need more information on the car to accurately say what speedo gears you need. rear axle ratio, tire size, and specifically what the speedo gears are in the trans now would be helpful. the drive gears are not a constant tooth count, they vary with tire size and rear axle ratio.

1974gmc · 03-03-2005, 05:26 PM

here is a kit my b&m search on summit racing part # BMM-70248

stick · 03-03-2005, 05:26 PM

Sorry I wasn't clear. I've got the formula to determine the speedo gear, I was just wondering if anyone knew what drive gear originally came in the transmission. He is running a 3.55 with 27 1/4" wheels and so I calculate a 21 tooth speedo gear with an 8 tooth drive gear.

stick · 03-03-2005, 05:41 PM

Thanks for the tip on the lockup kit. That's a cool option which I will show him. We were hoping that we would be able to wire it into the Nomad's system but he may just end up running without it. Guess we could just use a toggle switch but that's not a good solution either.

03-03-2005, 04:35 PM	#1
stick Registered User Join Date: Mar 2005 Posts: 3	Question on th 350 tranny I'm a new member and have a friend that just bought a th 350 tranny with a lockup converter out of an '80 Chevrolet half-ton. He has put it in a '55 Nomad with a new small block GM crate engine. Two questions. I'm assuming, in calculating which speedo gear he needs, that the th 350 has an 8 tooth drive (not driven) gear. I think the truck was a two wheel drive. Is that correct? Also, there is a single green wire coming out of the transmission which we are assuming is the on/off for the converter but we don't have a clue as to how to run the wire. Any ideas on that?

03-03-2005, 05:26 PM	#3
1974gmc In Progress Join Date: Feb 2005 Location: Kamloops, BC, Canada Posts: 312	here is a kit my b&m search on summit racing part # BMM-70248 __________________ 1993 Chevrolet K2500 454 4L80E 1974 GMC 1/2t 2wd Stepside 305 auto sold 1985 Ford Mustang GT 5.0 5spd

03-03-2005, 05:02 PM	#2
1FaastC10 Account Suspended Join Date: Oct 2002 Location: Elkhart, IN Posts: 6,399	need more information on the car to accurately say what speedo gears you need. rear axle ratio, tire size, and specifically what the speedo gears are in the trans now would be helpful. the drive gears are not a constant tooth count, they vary with tire size and rear axle ratio.

03-03-2005, 05:41 PM	#5
stick Registered User Join Date: Mar 2005 Posts: 3	Thanks for the tip on the lockup kit. That's a cool option which I will show him. We were hoping that we would be able to wire it into the Nomad's system but he may just end up running without it. Guess we could just use a toggle switch but that's not a good solution either.



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