On my next tire purchace I want to do a 2.5 in lift and increace tires to 33x10.5. I will be using the stock rims. I use it to tow a camp trailer and atv's. At what point do I need to change gear ratio, right now the rear axle tag shows 3.55.

Rich

 

You may be alright with only 33's, but for some extra towing power you may consider switching to a 3.73 or a 4.10. If you look around on the internet I know there are gearing calculators for different tire sizes.

 

thanks wakeboarder141. played with some calculators and the 3.73 looks like the best fit. I will need to find the optimum rpm for towing and the trans ratio for 3rd gear, then play with the numbers again.

 

If you have an automatic, third gear is direct, 1:1.

Here are some ratios for ya.

C6: 2.46, 1.46, 1.00. Also listed as: 2.47, 1.43, 1.00
(add 200-300 rpm for torque converter slip in a C6)
E4OD: 2.71, 1.54, 1.00, 0.71
AODE/4R70W: 2.84, 1.55, 1.00, 0.67
non-electronic AOD: 2.40, 1.47, 1.00, 0.67
ZF 5-speed: 5.72, 2.94, 1.61, 1.00, 0.76
some info I have seen shows ZF's with a 1.29 4th gear instead of 1.61.

 

i say move to 4.10's since you have OD it will tow real nice in 3rd and when your not you will have od to keep rpms at a decent level but still in its power range which is important.

 

I agree with Kemicalburns, on my 94 when I put the 4" lift and 33s on and still had the 3.55 gears it was real slow, plus the gas mileage went to pot (maybe something to do with foot constantly to floor to keep from getting run over?). I went with 4.10s, performance is much better, gas mileage is back about where it was before. I did have to recalibrate the speedometer to get the shifts on the E4OD to work right, but that's simple on the later Broncos. Plus if you decide later to go to 35s you won't have to change gears again, which you might if you stick with the 3.73s. But you will have to change the carrier on the front axle if you go above 3.92, so that is something else to keep in mind (good excuse to add some sort of locker, if you choose).

 

broncobob....when you change to 4.10s did you not have to change the carrier in the back to or just in the front. I am about to re-gear my bronco and just wanted to get the parts before i get it done.

 

I went to truetracs on both axles, so i did use a new carrier. But I'm pretty sure on the 8.8 there is no need to change if you don't want to. My thought was that if I was going to all the trouble and expense of changing gears, I may as well add some traction improvement at the same time. If you order all the parts at once, the place you get them should make sure they all work together.

 

Broncobob is right, no carrier break on the 8.8" rear axle or on the Dana 44 IFS/TTB front axle.

I also agree with Kemicalburns, 4.10 is a good ratio with 33's. With overdrive, you could go up to 4.56 and still be good on the highway. I run 4.56's with 33's, but I have no overdrive.

 

Dana 44 has a carrier break 3.92 down and 3.93 up

 

F100 is correct. There is a break at +/- 3.92. I also suggest swapping to 4.10s. I only have 31" tires, but I would love to swap out to 4.10s now. Our C350 has them with 31" tires, and I love the way it pulls. I still dont understand why Ford decided upon 3.55 for these trucks.


Rich

 

When you buy a gear and a kit to build it with does the carrier come with it or do you have to ask for it!

 

The carrier break is on the low pinion Dana 44. The high pinion reverse-cut Dana 44 is one carrier. Carriers are not part of the gear set. Order seperately.

 

http://cjford.stormloader.com/Tech/axleinfo1.htm