[68NovaSS]

Here's a couple of calculators.

http://www.wallaceracing.com/gear-speed.php

http://www.race-cars.net/calculators...alculator.html

[chevroletman223]

Thanks again for all the help guys! i apreciate all of your input! I think what i may end up doing is putting a set of 3.36's in, and if its revving too high for me on the highway, later in the year i could find an overdrive to stick in to compensate. What would be an easier swap? a 700 or a 200?

[Houston54]

I had a similar question awhile back and went with 3.42s based on responses I got here. This is a 10 bolt posi I was rebuilding to replace a 2.41 10 bolt posi I had under my 54 Chevy truck with a 355/TH350.

I drive the truck daily and found that while the performance was much improved off the line the cruising RPM turned out to be higher than I am happy with. I was getting 18-20 MPG previous and now am lucky to average 15 MPG in daily commuting.

If I were to do it again I would choose 3.08 gears for a street driven setup unless you change to an OD transmission. Then the 3.42 would be fine in my opinion.

[ap72]

Originally Posted by chevroletman223

Thanks again for all the help guys! i apreciate all of your input! I think what i may end up doing is putting a set of 3.36's in, and if its revving too high for me on the highway, later in the year i could find an overdrive to stick in to compensate. What would be an easier swap? a 700 or a 200?

I'd keep your current gears and do the trans swap first.

If you want to do an OD trans and gears then going with a 3.73 rear gear and either a 200r4 or a 700r4 will be fine. Without the OD the gears will be a pain in the ***, and with your current gears the OD will make your engine lug alongnad can create a lot of problems. a TH350 and 2.73 rear gears is fine for cruising on the highway and if its a healthy engine you will have no problem around town. You can also step the stall up a little (not too much though with 2.73 gears) if you want more pep off of a stop light.

[454C10]

much cheaper to put in a th350. And would yield much better results

first gear in a th350 is 2.52:1

first gear is a 2 speed is 1.70.

so installing a th350 would be like putting in 4.04 gears in with the 2 speed (in first gear).


2.52 x 2.73 = 6.8796:1 would be the 1st overall ratio for the th350 with a 2.73 gear.

1.70 x 4.04 = 6.868:1 would be the ratio with 2 speed and a 4.04 gear in 1st gear.

top gear would remain the same.

2nd gear in the th350 is 1.5:1 (almost like 1st gear in the guide)

[against all odds]

Actually, someone posted the chart online, so i just link to it:

http://www.wallaceracing.com/reargear.htm


It's copywrited stuff, so i have mixed feelings.............