Help on gears!

Ok so i just picked my 3rd XJ recently, all the previous ones have had at least 5.5 lift and 33's, but the gas mileage sucked! so now once i lift this one about 6.5 and 33's what gears size should i run for better gas mileage? what brand is good? i'm not trying to spend a great deal of money, but would like a some help in choosing a good set. so any info, webistes, and price quotes would be greatly appreciated! btw my new jeep is a 96'! thanks again

Hello and welcome to . You can find lots of helpful information by utilizing the search function.

If it's and auto go with 4.56's, we just put a set in a buddies jeep, and my brother's and it seems to be the perfect ratio for that size tire.

I have 4.10's and a five speed, but it seems to work ok for now...soon it will have 4.56's

Justin

xjjeeper19 said:

If it's and auto go with 4.56's, we just put a set in a buddies jeep, and my brother's and it seems to be the perfect ratio for that size tire.

I have 4.10's and a five speed, but it seems to work ok for now...soon it will have 4.56's

Justin

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should i do front and rear 4.56's?? or just rear?

Lifted98zj said:

should i do front and rear 4.56's?? or just rear?

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You need both front and rear......or your going to have big problems

C85D4x4 said:

You need both front and rear......or your going to have big problems

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awesome! so 4.56's F&R and as for the brand what should i go for and look out for? whats the best bang for my buck> thanks

C85D4x4 said:

You need both front and rear......or your going to have big problems

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Or big fun...:explosion

-Alex

I have 4.56 Yukon Gears up front and Genuine G2 Gears in the rear. I can't tell a difference in them. However, one shop wouldn't even install the Genuine Gears because they said they were crap and they wouldn't warranty thier work. I just went to a different shop for the install. If I were to buy a set I would probably go with the Yukon's due to their reputation. Regearing is expensive, so a few extra bucks is worth it I think. I simply looked at a bunch of websites and even found a few that offered free shipping and such.

For the best fuel economy simply Google "Gear Ratio Chart," or find it by searching through . Remeber that if you have an auto your rev's will be slightly higher. My XJ with 7" of lift and 33's runs a little over 2,700 at 65-70mph and I like it. My thoughts were that I only want to regear once so I went with 4.56's over 4.10's.

For prices I would just call a four wheel drive shop in your area for the install. Remember to get master install kits front and rear, because you are going to need them. My trick was to call a national four wheel drive chain in my area first (Four Wheel Parts). I got a quote that was a little higher than I wanted, so I then called smaller four wheel drive stores and found one that would do it for a reasonable price. Some stores will charge cheaper labor if you buy all the parts from them too, so factor that in when you ask for a quote.

Also, make sure they add in all anticipated oil disposal and shop fees in the quote, because that changes the total fee a little too.

thanks so much guys!

you can use this formula to calculate exactly where you want to be

Maximum MPH in each gear:

Formula: MPH = rpm x tire diameter (in) / gear x final gear ratio (diff) x 336
Example: Maximum mph in 280Z 5spd 1st gear using 6500rpm redline.
MPH = 6500rpm x 24.0"(tire dia.)/ 3.321(1st gear) x 3.54(diff gear) x 336 = 39.5mph
Note: Top gear is most likely hp limited, and would not be able to reach max rpm.

RPM @ 65mph (Derived from Max MPH formula):

Formula: RPM = mph x gear x final ratio x 336/tire diameter
Example: RPM at 65mph for stock 280Z 5spd
65mph x 0.864(5th gear) x 3.54(diff gear) x 336/24.0"(tire dia.) = 2783 rpm

FYI,

the manual that came with my Yukon gears limited the tire size to 32" for the Chrysler 8.25 axle or the warranty is voided.