I have a 61 impala ,283 ,with 370 ratio, automatic, want spin the tire with the370 gears, it would with 308, before i changs to 370s , what happen to off line power

You should have better bite with the 3.70 gears. Maybe, with the 3.08s, you didnt have enough torque to spin the tires. 283s aren't the torquiest motors.

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it did spin with 308s , maybe 370 takes more torque,

OK...I get it now... You get better traction with the 3.70s....Don't you feel better take off with these gears?

Spinning the tires doesn't get you anywhere....you want to avoid it.

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I agree, feels stronger, but 370s should spin easlier than 308, i think

Not true...the 3.70s will help get the power to the ground better, which is what you want for acceleration. Spinning the tires is a waste of energy.

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Well in theory they would spin if your engine was more powerful to begin with. Lets see if i can explain it in simple terms so that even I can understand it..lol.

OK here goes, to begin with your 283's peak torque occurs at a very low RPM. Not too mention the fact that its torque output is very weak overall. The 3.08 gear took advantage of that very low torque peak. It obviously made enough torque at that point that when combined with the rather heavy wieght of your car it was able to over power your tires. Now you've installed a much lower gear and though its multiplying your engines torque better its doing so at a much higher rpm. An RPM which is obviously well above your engines peak torque. Combine the fact that you've made it easier for your engine to get all that weight moving at a much more gradual increase in speed and becomes clear...lol What becomes clear you ask, well give me minute and I'll tell ya. The engine is applying less torque to the rear wheels because the 3.70 gear allows it to rev more quickly away from its torque peak than with the 3.08 gear. Your new 3.70 gear is asking your tires to move that heavy car forward at a much more gradual pace. All this exerts less pressure on the traction capabilities of your present tires. Confused yet? I know I am...lol. Bottom line is if you wanna spin your tires put taller skinnier back tires on or put some horsepower under the hood to go with that new gear.

Doc

i understand, thanks alot, doc

i have a 3.08-geared '64 and would like to do a gear swap sometime in the future... I would be interested in knowing what parts you used... what was the cost, and how easy was the procedure?? thanks!
-matt ramsey

i bought a 370 center carrier for 140.00 from ebay, as for change out, take brake drums off,unbolt bearing retainer 4bolts , pull axles with a slide hammer,unbolt center carrier 10 bolts, be careful,it is heavy, pull it out, make sure you use good safe jack stands ,buy the way,in the south we call it a hoghead

Did you change the rear end carrier from a single track to a limited slip? If so that explains the no spin, you doubled your traction........Did you change the pinion gear? you didn't mention it in the above replay.

no, its a open carrier, from a 308 to 370s

That doesn't sound right to me either, with that gearing change you "should" have been impressed with the end result.

I went over an even broader gearing range when I changed the factory installed 2.29's to a set of 3.73's.

It would just barely turn the tires on wet pavement, and that's with the transmission first gear of 3.06.
I swapped the gears in a few hours from a freebie set out of a trashed S-10, and the result was better throttle response, better mileage, and an occasional chirp from first to second, with better ability to use the overdrive gear. As long as there is traction at the start, there is a neck snapping result.
You "should" have similar results.

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what size motor, what kind of car do you have, 2 mechanic said i should spin 1 tire , 1 is a drag racer, 1 said it might transfer weight better with 370 ,

The yellow 1981 Malibu in my avatar.
It still has the original 267 with 173,000 miles on it, the only things that have been changed on it are the cam, lifters, timing chain/gears, and fuel pump.

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