Im thinking 4:10 but not sure. Does the EX have a DANA 60 in the rear and DANA 50 in the front? Where is the best place to order from?

 

what year is your ex the rear is a sterling 10.5 and i'd say4.56 or 4.88's with 35's. all the v10 guys i've talked to either have or want 4.30 gears with stock tires

 

its an 05 with the 6.0 a 6 inch lift with 35s. I tow a 25 ft trailer and its just a little too tall of a ratio right now. Im assuming the ex came with 3.73 stock right? If anyone has a similar set up, im thinking either 4.10 or 4.30 in that area.

 

sorry man i was reading some v10 stuff before i posted and for some reason got confused and assumed you had a v10, 410's if its mostly flat land and 4.30's if you haul in hill country

 

33"s are 32.8 inches in diameter (average)
35's are 34.6 inches in diameter (average)
37's's are 36.6 inches in diameter (average)


The Effective ratios in relation to the OEM tires are as follows:

33's:

4.10.....3.96
4.30.....4.15
4.56.....4.40
4.88.....4.71

35's:

4.10.....3.76
4.30.....3.94
4.56.....4.18
4.88.....4.48

37's:

4.10.....3.55
4.30.....3.72
4.56.....3.94
4.88.....4.22

If your tire is exactly 33, 35, or 37, then the chart looks like this:


33's:

4.10.....3.93
4.30.....4.12
4.56.....4.37
4.88.....4.68

35's:

4.10.....3.71
4.30.....3.89
4.56.....4.12
4.88.....4.41

37's:

4.10.....3.51
4.30.....3.68
4.56.....3.90
4.88.....4.17


If you have been comparing what gasser folks here and elsewhere have been regearing their axles with oversized tires, you find a lot that try to be conservative and choose too high of a ratio.

You need to think about where you want to be if you were with the original tires and wheather or not you are towing or want better mileage.
Also, remember that the larger the tire, the worse the rolling resistance, and that calls for a slightly lower ratio to overcome that.


However, with a diesel and the torque it gives, you really just need to keep your effective ratio near or just a little lower than the OEM 3.73.

Looking at the charts, that puts you, as Fatdan said, using the 4.10 or the 4.30's. For the diesel, I would go for the 4.10.s to keep the engine RPM's up near the same as the OEM rate. But, if you are going to 37's, then get the 4.56. (edit: ooops. that should have been 4.30)

 

As someone who has personal experience with this, if you own a diesel truck:

35s= 4.10
37s=4.30

4.10 gears will get you back your stock power and fuel economy, 4.30 gears with 35s will put you above this and your truck will run out of steam at the top. Trust me, I know this first hand...

The dicussion started here on the 4th page and it ended on page 7: https://www.ford-trucks.com/forums/6...y-caved-4.html

All in all, a very expensive lesson learned...

 

I heeded all this good advice before Christmas when I re-geared (and added LSD) to 4.10 because of my new 35" tires.

It worked for me.