Changing gears in my SCREW from 3:55 to 4:10.

Currently I have 31.5" tires which are 1.5" taller than the originals. With these tires my engine is turning 2000 rpm at 75mph. Anyone know what my engine rpm will be at 75 mph and the new 4:10's?

Is ther an online calculator for this?

 

2310 RPM @ 75 MPH with same tire's @ 4.10 gear.

 

Thanks Gearmanx17. Does Ford sell 4.10's or do I have to go aftermarket. If so...all I can find is Richmond Gears. Any good?

 

There are many quality manufactuer's of differential ring & pinions. I have had good luck with OEM Ford and U.S. Gear.

Some of the other brands include: Precision Gear, Motive Gear, Auburn Gear and others (whick I cannot think of).

If you do not have the experience or Technicial expertise to do the gear change, I would highly reccomend using a professional to do the job.

Countless times I have seen un-experienced people attempt a rebuild or diff. gear change--wasting alot of $$$.

Good Luck, Gearman

 

Dan, 4.10 is a ratio that should be available. Do you have the 8.8" or the 9.75" diff.? Is your S/Crew powered by a 5.4L or 4.6L?

If S/Crew has 4.6L--Your truck should have 8.8" diff. If Truck has 5.4L--then it should have a 9.75" (ring gear diameter) diff.

 

Wow...I just thought I had the 8.8. I have the 5.4 ltr engine. Now I have to climb under my truck and determine which diff I have. Is that a hard stedfast rule that the 5.4 gets the 9.75?

 

YES

 

You were right. It's a 9.75. I wonder how much a set of 4.10's will cost!

 

The 9.75" gears cost more and have less ratio variety. Decent gears alone run about $275.