I have a 99 4x4 f150 5.4 and the original window sticker says it was custom ordered with a 3.73 something or other...what's that mean?

 

3.73 means you have 3.73 Limited Slip gears

 

is this good or bad, and what does it do to my truck? I see people's signatures saying "3.73 coming soon" or something like that...why would people want 3.73 limited slip gears? Is this in the differential?

 

my 07 4x4 F150 4x4 has em and i love em limited slip is where if 1 tire loses traction the truck will send power to the other tire to try and get traction or somethin like that, correct me if im wrong... and most if the time peoples sig's say "4.10,4.56, or 4.88 coming soon" because they need more power then the 3.55 or 3.73 to push their big beefy tires.

 

The number refers to the number of times the axle will turn in proportion to the number of times the drive shaft will turn. 3.73 means that the drive shaft will have made 3.73 revolutions for every 1 turn of the axle. The engine will rev substantially quicker putting you in the engines effective power band sooner. This can be of great help to engines that need to pull a heavy load but aren't making enough torque in the lower range. Steeper gears are used to increase the acceleration of vehicles in many cases as well. With the 5.4 and stock tires I am sure your truck should get up and move.

 

well yeah my truck used to have stock tires, and it did get up and go, but now i put on some 285/75/16's. I haven't noticed a power loss (probably is one) but it does drive better.

 

BTW, the axle ratio has nothing to do with wether it is limit slip differential.

Check the axle code on the driver's door sticker to confirm if it is open or ltd slip. 26 = open and B6 = limited.

I ordered my 99 Supercab with the 5.4L and 3.73LS. I loved that combo. My Supercrew with that combo is not as good, even if I added 300 pounds old truck in the bed to compensate.

 

Think of it as pedals on a bicycle.

When you were in the biggest gear, and you were stopped, when you wanted to start going, you had to really put a lot of energy (RPMs) into turning the pedals once in order to turn the tires once, right?

Now, imagine you put really big tires on your bike that were a lot heavier. Now it would be even harder from a stop to push the pedals to turn the tire, right?

Well, steeper (higher numbered) gears mean that it takes more turns of the pedals (driveshaft) to turn the tire once...but it means your feet don't have to try as hard (fewer RPMs).

Thus, it kind of brings how hard the engine has to try (RPMs) back to how it was with normal gears and stock tires.

If you have stock tires and higher-numbered gears, then it usually increases acceleration from a stop.


There is not a HUGE difference between 3.55 and 3.73 (5% increase in driveshaft turns). There IS a big difference between 3.55 and a 4.56 (28% increase) and 4.88 (37% increase).

 

Try 3.08 to 3.73 on a 4.6

Now THAT is a big damn difference.

I don't need 4.10s. Ill save that for the race car.