A gear question?

[MJRemi]

88 MJ 4.0 2wd 5spd. I will soon be swapping in a AX15 (2wd) and, if I can afford it, thought of swapping gears and maybe even axles. For street use only, does it matter if I just keep the D35 or should I upgrade? And whichever axle I use, which gearing would be the best ratio to have decent acceleration with not much concern for high top end speed? Thanks!

[jimoshel]

The D35 is very adequate for street use only. 4.10 or (4.11) for acceleration.

[dasbulliwagen]

For a street truck, with stock tires, and a 4.0, I would not go over 3:73, and might even do 3:55. The 3:73 is commonly available in Ford 8.8 axles or on 35's from Grand Cherokees, or 8.25 axles from Liberty's. And the 3:55 can be found in 35's from 4 cylinder 4 speed MJ's and XJ's.... I'm assuming you currently have 3:05 gearing right now, so anything will be an improvement, but if youre not running big tires, I wouldnt go too far... especially when you have the torque range the 4.0 has. I just think that going to 4:10 will just make it revvy, and ruin your gas milage too much.

[Pete M]

do NOT pay to regear a Dana 35. They are NOT worth the investment. grab a 35/44/8.8/8.25 from the junkyard with the better gears already installed. :thumbsup:

 

What size tires are you running?

[jimmy21669]

Agreed, it is cheaper to just pick up another axle with the right gears, and upgrade at the same time.

 

From 3:07 to 3:55 will put some pep in your step if you are keeping stock tires. A 3:55 MJ axle should be easy to find, but better yet, if you have the means to move the perches, there is an OVER abundance of 3:55 XJ axles out there in 4.0 automatics. Then you can get the 8.25.

 

My local JY sells them for $85. Regearing can cost $400 just to do it yourself, let alone if you have someone else do it.

[kyleag89]

:agree:

[MJRemi]

Thanks for all the input guys! I didn't realize it was so expensive to re-gear. I'll keep my eyes open for a good deal on axles, but how do I know what gears they have if the seller doesn't know? Is there a tag or stamp? I'm not sure what to look for.

[Geonovast]

Oh yes, and if you ever read a how-to on re-gearing, you'd understand why. You can't just bolt new gears in. They have to be extremely meticulously adjusted.

 

To figure out gears, the easiest way is to pop the cover and look. There should be a stamp on the ring gear with at least the tooth counts, but probably the ratio itself too.

 

If it's just got the tooth counts, divide the bigger number by the smaller number.

 

Ex. if the stamp is 41 10, 41 ÷ 10 = 4.10

[Pete M]

...extremely meticulously adjusted...

 

 

I've been looking for a phrase that adequately described setting up gears... :D

 

 

 

Another way to check (if possible since brakes sometime lock up in the junkyard) is to spin one of the axleshafts and count the number of times the yoke spins. If only one axle shaft turns, rotate it around twice. If both axle shafts turn in the same direction and at the same rate, turn the axle shaft once. If they spin in opposite directions, you're going to need to get one to stay still while you turn the other twice.