My 2001 Off road package has limited slip 3.55 ratio. What does all of this mean? Is 3.55 pretty standard in this year truck? Might sound like a stupid question, but I'm learning. Thank you!

 

That means that for every revolution of the tires the driveshaft turns 3.55 times. It also means that if one rear wheel starts spinning due to low traction the other wheel should keep pulling.

 

that also means don't go larger on the tires until you re-gear

 

My 2002 FX4 also has a 3.55 limited slip in the rear. Some had 3.73 gears, but I think most had 3.55s. Later years the wheels are larger and more have 3.73s. Most of the miles I put on mine are highway, mostly interstate highways running fast, so I'm happy with the ratio.

 

The 99 that I own now has 3.73's. My previous 99 (Identical trucks, same engine and drive train also) had 3.55's. And the 00 I parted out, same engine and drive train as well had 3.55's.

 

Oh ok...so the 3.73 ratio would give you slightly better MPH on the freeway? And 3.55 would be suited more for pulling?

 

The higher the gear ratio the easier it is to turn the tires. So it would be the opposite of your question. Most people regear to a higher ratios like 4.10 or 4.56 when using bigger tires or wanted to pull more. You will lose more on the top speed, but get there quicker.

 

other way around 3.73 for towing 3.55 for highway i have 3.55's tow a 5000 pound boat just fine and get ok highway miles without the boat

 

I got it now...thanks guy's

 

it's the lower the gear ratio (higher number) that will increase the torque applied to the tires, and the higher the gear ratio (lower number) less torque applied at the same given rpm.