Quote:
Originally Posted by firebird_1252
how would a truck with 2.64 rears do with pulling weight? at gross? the truck in question is a walmart truck. i heard somewhere that its basically 3.55's because the trans is direct and not od. true?
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You have to look at the TORQUE at the wheels. Take ENGINE Torque X Top Gear Ratio X Axle RATIO. This way you'll be able to compare different trucks. My example: torque is 2,050 lb-ft; top gear ratio is 0.73; and axle ratio is 3.42; so my torque at wheels is
2,050 x 0.73 x 3.42 = 5,118 lb-ft of torque
WalMart truck (I'm guessing)
torque - 1,650
gear ratio - 1
axle ratio - 2.64
Torque at the wheels: 1,650 x 1 x 2.64 = 4,356 lb-ft of torque
If this was a regular setup with 3.55 rears and 0.73 top gear ratio (13-speed), it'd have:
1,650 x 0.73 x 3.55 = 4,278 lb-ft of torque
So, the Walmart truck would pull a little bit better in the top gear than the truck with the 3.55 rears, provided they both have 1650 torque.
When I had 3.73 rears, I remember my wheels were spinning on a wet pavement going at 58 MPH up a hill in Texas. Here's why - with 3.73 axle ratio I had 2,050 x 0,73 x 3.73 or 5,581 lb-ft of torque at the wheels!
This formula doesn't take into account the tires - with smaller tires you'll have the truck pull harder and accelerate a bit faster.