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80camaroguy 01-22-2013 10:23 AM

what rear gear should i use
i have a 1980 camaro with a sbc vortec 350 out of a 99 truck i currently am backing that motor up with a 3 speed saginaw and i think a 2.73 rear gear open i was wantingto change to at least a 4 speed saginaw and a posi i just am unsure of which route to go or if i can find a 5 speed from a late 80's model if that would be a good choice or not

big gear head 01-22-2013 11:20 AM

Use a period sometime!

The 3.42 gear was very popular in those cars. It's a good all around gear. Many late '70s automatic Z28s had those gears with the Traction Lock differential (posi). If you look around enough you can probably find one for sale. If you decide to go with new parts I recommend the Eaton Posi, Yukon or US Gear and a good installation kit. Randy's Ring & Pinion or Tom's Differentials are some of the best places to get these parts.

80camaroguy 01-22-2013 11:43 AM

would that gear be good for gget up and gobehind the 4 speed. or even posibly a 5 speed

techinspector1 01-22-2013 12:29 PM


Originally Posted by 80camaroguy (Post 1637638)
would that gear be good for gget up and gobehind the 4 speed. or even posibly a 5 speed

The Saginaw will not take much abuse.
Shoot for a 10.0:1 first gear final drive ratio and a close ratio gearbox.
This would be my choice for you if you're bucks-up....
Richmond Gear 7021710A Richmond 5-Speed Street Transmissions
Richmond Gear 49-0001-1 Richmond Gear GM 10-Bolt Ring & Pinion Sets

Match the 3.28 first gear of the 5-speed with a 3.08 rear gear and find a first gear final drive ratio of 10.1:1.

5th gear is 1:1, so with the 3.08 rear gear and a 28" tire, the cruising rpm's at 60 miles per hour would be 2,250. Cam the motor accordingly. If you screw some fosdick long duration cam into the motor, you'll be steppin' on your.....toe.

If you're not bucks-up, try to locate a '66-'74 Muncie 4-speed with a 2.52 first gear.
Mate it with the 3.54 rear gear suggested by big gear head for a first gear final drive of 8.6:1 or use a 3.73 rear gear for a first gear final drive of 9.4:1.
Muncie Transmission Id and ratio guide

big gear head 01-22-2013 01:21 PM

With a 4 speed the 3.42 would be middle of the road between good take-off performance and highway use. The 3.73 would be more of a in-town gear. A 3.23 or 3.08 would be a little better on the highway, but a little less exciting from a stop light.

With a 5 speed the 3.73 would work well, but the 3.42 would still be a little better if you are on the highway more. Tire size also has something to do with it. Taller tires are going to slow down acceleration some, but lower RPMs on the highway.

vinniekq2 01-23-2013 07:51 AM

gear ratio choice depends on the application of the car.How did you end up with a 3 speed saginaw in your car?

Gear Ratio Speed Calculator
I use a 3.50 gear and a 5 speed for my application.

80camaroguy 02-01-2013 12:26 PM

it came with it the guy i got it from took out the original v6 maybe 3-4 years ago

big gear head 02-01-2013 01:17 PM

V6 or inline 6? I thought those cars had the inline 6 in them.

80camaroguy 02-06-2013 06:23 PM

it did not have an inline six but thats not saying somone before him didnt swap it also

prostreet6t9 02-06-2013 06:28 PM

I'd do the 342's also unless you have 28" tires.

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