I think I've read all the gear threads, but couldn't find what I was looking for. Does anyone sell the 4.27 or 4.56 gears yet for the JK X 6-speed? I just installed a 4" lift and 315's (34.4"), and it's sluggish. Still driveable, but can't use 6th gear at all, and seldom 5th. I see a lot of talk about 4.88's and 5.13's, but all my research and talks with shops seem to indicate that I need 4.56's. I seldom go off road -- mostly drive in town. My fear is that 4.88's might be too much. I don't want to be turning 4000rpms at 70 mph in 6th gear. I may go to 37's later, but my 315's are brand new. Thanks for any help.

 

Nothing available that I know of except 4.88's and 5.13's.

 

This isn't perfect, but maybe it will help you a little.

 

Thanks, guys. Forgot to say I've currently got the 3.21 ratio with the 315's. Am I doing any damage to the jeep with the current set up? Looks like from the chart above I could maybe expect to be in the upper 2000 rpm's at 65 mph in 6th gear with the 4.88's? That doesn't sound too bad, does it? I'll likely go to 37" tires after the 315's wear out. Should I wait for the 4.56's to come out, or go with the 4.88's now?

 

I dont have my JK yet, but for what its worth:
On other vehicles I have owned, 4.88s and 35s are the best combination of power/fuel efficiency. No way I would consider less (numerically) than 4.88 with 37s. Really should be 5.13 with 37s IMO.

 

Thanks, Greg. I think I'm going to go with the 4.88's. I'll be hanging on to the 35's for a while as they're new, and I don't log a lot of miles, so the 37's will be a long way off in the future. I've got to think the 4.88's will be a vast improvement over the 3.21's I currently have in there now.

 

When you change your rear gear do you need to change the front to match

 

Yes, both front and rear gear ratios have to match so the front and back are traveling the same speed.

 

Has anyone tried to use this chart? I was driving home today and at 65 in 4th gear I was setting rite on 3000 rpm. Acording to the chart I have 4.11 gears, but my window sticker says I have the 3.21. What do yall make of this????

 

I called 4 Wheel Parts today to inquire about the 4:88 gears, and they told me that Superior has been having trouble with the new gears. They suggested that I wait until later in the year when more companies are making them and all the bugs have been worked out. Anyone hear of this before?