what is the difference in a 3.55 limited slip rear axle to a 3.73?

 

The 3.73 will give you more torque at the wheels, but increase your RPM's slightly. I believe at freeway spped the difference is lesss than 200 RPM.

 

so what is the difference say on pure speed if the same truck raced with different ratios who would win?

 

A truck that has a 3.55:1 gear ratio means that the driveshaft will have to spin 3.55 times for every 1 rotation of your wheel. Likewise, a truck with a 3.73:1 rear end, the driveshaft will have to make 3.73 rotations to complete one revolution of the wheel. What does this mean? The 3.73 will have better launching capability, as well as slight towing advantage (mechanical advantage...think of these working like a lever). The 3.55 will theoretically be better for highway driving, since you wont need to spin the driveline as fast as with the lower gears. In all actuality, I have found the 3.55s to be too tall for trucks, and far prefer 3.73s for everyday use. As for limited slip, that is a carrier that sits in your rear axle housing, which directs force to your wheels. Most standard trucks come from the factory with what we call an 'open' differential. There is no traction modifying device installed. The engine power will be directed towards the wheel with the least amount of traction. With a limited slip, or locker unit (diff from limited slip), those both direct power to both wheels evenly, to provide equal traction to both wheels. They have their pros and cons. They give great traction for when you are towing a trailer, pulling a boat out of the water on a slippery inlet, and general offroad use. The con is that they can provide unwanted performance in icy conditions. Since they want both wheels to be spinning somewhat the same, when you encounter ice, that can cause the rear to break loose. I personally love limited slips, and have one in my current truck. As for who would win...that has so many variables, its not even funny. Are you running the exact same tire sizes, rims, transmission gearing, octane, cubic inches, driver skill, vehicle weight, etc and so forth.


Rich

 

Everything being equal, the 3.55 geared vehicle would have a theoretical higher top end. That's if the engine had the power to push it.

 

thank you this was helpful to me, i wasnt sure what limited slip meant. my scab came with 3.55 gears and lim slip as an option.About how many rpm's you run at seventy?

 

I dont know. I will let you know the next time/first time I go 70 (just got my truck ).


Rich

 

At 70 I am just a hair below 2000 with the 355.

 

yes mine is about 18 to 1900 rpms at 70

 

I have 3.55 gears and Im ajust a hair above 2000 with Limited slip short bed, standard cab 5.4...

 

Right, but who's running 17" wheel/tires and who's running 18" wheel/tires??

My Lariat with 275 x 65 x 18" turns about 1950rpms at 70mph with a 3.73LS.. Thats axle code B6 on the door sticker..

 

Right, but who's running 17" wheel/tires and who's running 18" wheel/tires??

My Lariat with 275 x 65 x 18" turns about 1950rpms at 70mph with a 3.73LS.. Thats axle code B6 on the door sticker..