2008infantry

Okay, so I was doing some research about gearing my jeep and got kinda stuck. Im running 3.5in lift and 31's, I dont really plan on going any bigger with the tires.

I have the Crysler 8.25 in the rear and a Dana HP30 in the front. I was looking for the best gear match for those to max mainly my onroad drivability but also a bit more power offroad. I figured 3.97 would be the best upgrade from the 3.05 gears I have now. The only thing is I dont know is what gear ratio would be the closest match for my D30 to the 3.97 Gear ratio I decided on for the C8.25.

NorCalJeep

They have 3.97s? Why not go with 4.11s?

2008infantry

From the research I've done the 3.97 will give me the best fuel economy and power and speed mix. 4.11 would give me alot of power offroad but retard my speed and fuel economy.

Atmos

for D30 they make a 3.73 and then it jumps to 4.10. you can regear or find some stock xj axles at a junk yard that have those gears from the factory and swap (3.73's being semi-rare). unless you have deep pockets and some free time on your hands it's kind of a waste of effort on 31" tires

here is a thread with someone who asked almost the exact same question.
http://www.jeepforum.com/forum/f11/r...3-90-a-591203/

01mainexj

397 and 410 are so close it won't make a huge difference I would just step down to them then go with 373 if you really want to regear for 31s

71chevytruckguy

Id run 4.10s, you'll never feel the difference from that and a 3.92

2008infantry

Okay, well thank you all for the reply's and advice.

RubberSideUp

I ran 4.56 with 31s for years. Really wakes things up. Probably the best combination you can get with the 30/8.25 in terms of improved acceleration. 4.88s have tiny pinions and I don't recommend them. This is not to say they won't survive, but it's expensive if you're wrong. If I was gearing a 30/8.25, I wouldn't consider any thing other than 4.56 gears for 31-35s. Do it once, do it right. JMO.

VTJeep

Umm.. The same?