Ok folks, I am sorta ignorant about this sort of thing but, I was wondering what the difference in a 3.73 vs. 3.55 rear end. Is one or the other better? I just bought a 2001 Supercrew King Ranch 4x4 that came with a 3.55 with Limited Slip. None of that makes sense to me. Help??

 

I will try a simlified answer since that is all I am capable of. There are two gears inside the rear end housing that that work off each other to transmit the turns of your drive shaft to the wheels. the ring gear and the pinion gear. What the number signifies is the number of revolutions the pinion gear has to make to equal one turn of the ring gear. Thus, the higher the number, the lower the ratio. That means that the higher the number equals more "digging" power. So, if tires are the same height, the 3.73 will have slightly more power than 3.55s but will use more gas as the engine has to turn more RPMs at the same MPH. Then there are 4.10s, 4.56, 4.88 and so on. I ran a small block Falcon( a 1965 289) with 5.56s with a 4 speed tranny. It topped out at 100 mph, but got there in a hurry. hope this helps.

 

BTW, see you are in Everman. Come through there all the time. Live East of Burleson, work in Grand Prairie. You work at the station on Everman Parkway?

 

Nope, I volunteer for the Everman Fire Department but work for Arlington FD - Station #2 (Sherry and Pioneer Pkwy, near 360) which is the busiest Engine Company in town. By the way, I like what you did with the fog lights, is that stock? I am partial to the new body style Ford's. I just wish I was able to afford one in the King Ranch variety, but on a Fireman's salary (with no part-time job) it just isn't gonna happen. Take care!

Oops, and thanks for the answer on the rear end question!

 

You also said that it has Limited Slip.
So if you would like to know about this too I will try to explain it.
The Ring Gear that he told you about really does not turn the wheels.
It turns the Differential Case and inside the Differential Case there are four gears. Two are the Pinion gears that are pinned to the case and two are the side gears that the axle goes into. The pinion gears drive them.
The side gears are clutched to the case and have a spring pushing them toward the case. Now in order for one wheel (axle) to turn more than the other the clutches on both sides have to slip. As the truck gets older they slip more and more until you have to put in new clutches.

In short this gives you a lot more pulling power on slick surfaces and in mud but no help at all on dry surfaces unless you are drag racing.