BroncoII4x4.com

I called jaws gears the other day and they recommended getting 5:13 gears with a stock B2 2.9 5 speed and 36 inch tires. I have 3:73 gears right now with 36's and I do ok on the road. I was hoping people out there could tell me what you are running and how you like it. You know gears, engine, tranny, etc. I was told that the 5:13 will have me at 2200 rpm at 65 mph.

Search Google for Gear Ratio RPM and you should should come up with lots of hits for charts and calculators like the one below. Your motor will need all the help it can get, so 5.13's would be good. Except for the fact that at that point the pinion is getting pretty darn small.

This one is for 65mph in direct drive (no over drive)

Thanks! I think 5:13 will be what I go with. I have the 8.8 and 35 so the pinion wont be too small.

what does the yellow, black, and blue mean in this chart

Black is about where you want your gears, yellow will put a little extra strain on your motor, blue is putting your gears a little high.

Black would be the recommended range. Factory gear ratios typically fall in the black.

Blue is will make your engine run at a higher RPM for a given speed. This gives you more seat of the pants power at the cost of fuel economy and driveability. You'll be looking for another gear to shift into on the freeway.

Yellow will make your engine run at a lower RPM for a given speed. This typically will help fuel ecomony, but you'll be slow off the line and down shifting for the hills more frequently.

So before you regear, you need to make an honest assessment of how you will drive your Bronco, both now and in the future. If you see much freeway time, then you really should stay in the Black. If it's trailered, or never driven on the freeway, then you can go ahead and gear it out into the Blue area. The only time I'd recommend the yellow is if you have a lot of low end torque/HP.

The other thing to consider on this chart is the gear ratios. Only some of those are commonly used ratios. 3.42, 3.55, 3.73, 4.11, 4.56, 4.88, 5.13

i kinda figured that black was where you wanted to be but i wasn't sure, i think i want to run 38's now, so i think a 5.13 or 5.38 will work good its a 2.9 5-speed

what year of b2/ranger/explorer did they put 4.10 gears in? and what years had the limited slip units in them? anyone know? and if i run 3.73 in rear do i need to run the same in front? or will it drive fine with mixed matched ratios...

as long as you dont put it in 4wd and keep the hubs unlocked it probably won't hurt anything for a little while, but you will need to change them eventually, my 89 B2 has 4.10's atleast if not lower and its factory, not sure about the limited slips though.


i have a question if anyone knows, my B2 at 65 mph in 4th gear which is direct drive according to the chart above is turning 3600 rpms, but i have 235/70's on it right now, i think thats about 27 inches, is that right or does anyone know how to convert that 235/70 over into inches

Yeah, that should be in the 27/28 range. Search google for "tire size conversion". Your RPM seems a little high. Do you have a 5sp or automatic? Autos rev a little higher because of torque converter slip.

its a 5-speed, according to that chart if their 27 inches tall( and i measured them and the best i can tell they are a hair over 27 inches tall ) then thats a 4.56 gear, did they put gears that low in any of them from the factory?

Maybe it's your tach that's off. I'm pretty certain 4.10's are the lowest factory option for a Bronco II. It's possible someone could have swapped gears, but I kind of doubt it on a stocker.

See if there is a data tag on your front or rear axle. Usually bolted to the cover bolts. Also check the door jam for the axle code.

yea the tach may be off a little, but it sounds like its twisted up there pretty good and i'm pretty sure its the factory gears, my dad bought it in late 91 so unless the gears were changed before that they are factory

Mine is a 89 with 4.10 locking factory.But they have had 4.10's since 80 I'm pretty sure.They just aren't very common.