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?

 

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.

 

tracer that mumbo jumbo actually makes sense! now theres a bit of a twist to these trucks. they were bought from the walmart fleet with bad motors. a newer isx was put in them. he has a few of them all the same way. some can be turned up to 500 hp, some 565. so the tq might be higher. now my next question is, with that ratio is the fuel milage around the same as 3.55's?

 

When you're empty or lightly loaded, fuel mileage should be the same. Loaded you should do a little bit better with the 2.64 axle ratio as the torque is higher at the wheels, so the engine has to burn a bit less fuel to achieve the same speed. I would go for an engine with the highest torque and drive the truck at the lowest RPM. Good: 475 HP, 1,850 torque. Bad: 500 HP, 1,650 Torque.

I have a load of steel plates right now heading west on I-94 in MI (45,000 lbs) and the truck pulls like there's no tomorrow at 1,270 RPM (!). At that RPM I'm still at 59 MPH and I hardly burn any fuel. I've been receiving threats from fuel station owners along the route

 

thanks tracer!

 

My father has been driving for Wal-Mart for close to 30yrs now. He said that the old IH's got around 6.5mpg and the Columbia's avg between 6.8-6.9 most times. I am guessing this one has an APU on it as well??? That would be nice

 

yes sir it has the apu. i wouldnt mind a columbia i'm a weird one.. i do not mind the 14l detroit. shift under 1500 rpms going though the gears even at 70 they'll pull down in the 7's mpg.

a while back i saw a 03 (pre egr) walmart columbia.. gone though. also found some ex swift trucks too...

 

Yup 2.64's and 3.55's are very close to each other when matched to their respective 10 spd(in all gears, 1-10). If you think that's a lot of torque, do the calculations on low gear!