My truck is rather sluggish. It has 3.42 gears. I am thinking of putting in 4.56 to increase accelleration a bit. I don't want a race car, but it would be nice to improve the pickup of my pickup (pun intended).
Is this a good idea?
Low gears
May 29, 2006
9 Replies
"Shep" wrote in news:1148946265 snipped-for-privacy@sp6iad.superfeed.net:
It's a 1987 c20 8600gvw, 33" tires
Yes what ires size, vehicle type and engine and planned usage.
----------------- The SnoMan
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If it has a TH700, 4.56-5.13 gears should be fine, just don't plan on running down the freeway in 3rd...If it has a TH400 or TH350, I would suggest a 3.73-4.10.
GM ECM's support up to 4.56 axle ratios from the factory. (they need to pe reprogrammed though to use it.)
This site has a calculator based on your input of tire size, transmission type(ratio) and tire diameter. It allows you to compare diffrent rears and look at your road speed vs rpm. Depending at what speeds you normally travel and the engines power band you can make your own decision.
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Its an awesome 'Calculator', but like all the others, it doesn't factor in slippage in an automatic trans. 10-15% is the norm even with a lockup converter.
I was referring to slippage causing 10-15% higher RPM.
The RPM that a lock-up converter drops is directly related to speed, amount of power, weight, and RPM itself. Under little to no load, it might only drop 10-20 RPM, under heavy throttle and heavy load, it con drop many hundred RPM.
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