gearing issue

[bagdranger]

hey guys my little sis has a 89 ford f150 with 35s and she needs to get it regeared for the 35s. the truck has 3.55s in it. my question is what should it have. I was thinkin like she needs a high 4 like a 4.75 or somethin in the neighborhood of that?

 

[wahlstrom1]

If you spend a lot of time on the hwy I'd go with 4.56's, otherwise 4.88's are a good choice.

 

[bagdranger]

4.88s sound good. she doesnt do a terrible lot of hyway driving. but once its geared itll be pulling a loaded horse trailer so 4.88s probably be best. know where i can get a ring and pinion set.

 

[wahlstrom1]

Contact Jim Oaks, TRS's founder and order a set through the site. Otherwise any local 4xshop or manufacturer should be able to sell you a set. Stick to name brands like yukon/genuine/US Alloy/superior etc for the best quality.

 

[CJREX]

For the FS Bronco and F150, you need either 4.10 gears (5% over stock) or 4.56 (5% under stock) to be close to stock gearing.

Here is a quick gearing chart from fullsizebronco.com

Stock 29" tire (235/75R15), with 3.55 gears, 90.7" is circumference of tire, thus for every turn of the drive shaft, you go forward 25.5" or so.

33" tire, 3.55 gears = 103.7" circ, forward 29.2", about 15% more than stock
33" tire, 4.10 gears = forward 25.3" basically same as stock
33" tire, 4.56 gears = forward 22.7", about 11% less than stock

35"s with 4.10s = 26.8, 5% over stock roughly.
35" tire, 4.56 gears, 110.0" circ, forward 24.1", about 5% less

37" tire, 4.56 gears, 116.2" circ, forward 25.5", identical to stock (within error)
37" tire, 4.88 gears, forward 23.8", about 9% less than stock.

38.5" tire, 4.56 gears, 121.0" circ, forward 26.5", about 4% more than stock
38.5" tire, 4.88 gears, 121.0" circ, forward 24.8", about 3% less than stock.