- Location
- Foresthill, CA
If I see another thread about choosing gear ratios, I'm going to have to slit my wrists with a butter knife. In the interest of me living through the next week, please read the following:
Gearing is a subjective issue. A guy who lives in Florida may have different preferences than a guy in Arizona. Yet, there are general rules which apply, based on a lifted XJ with an overdrive transmission. In GENERAL, on a 4.0 that is in good condition, you want to keep the revs at or below 3,000 at max cruising speed. As an example, I've made very good mileage at 2,750 with 35" tires (18 mpg). Don't be afraid to spin the little 4.0, as it is an undersquare motor, i.e. a short stroke motor. If you have the unfortunate experience of owning a 4 cylinder XJ or a V-6, disregard the following and go to 4.88's for any tire size larger than 30". So general gearing guide from your friends at URF:
30', 31's: 4.10 (don't do something stupid like I did and go to 3.73. Hey, I was a freshman in college at the time.)
32's, 33's: 4.56 (If you live in the mountains, or your rig is on a trailer a lot, put your purse down and go to 4.88's)
35's: 4.88's (Only because you can't get 5.13's in a Dana 30. If you live in a state that has a SINGLE rock you may one day want to climb, ditch the 30 and step up to a 44 and 5.13's)
37's: 5.38's will do you nicely, but your still going to want deep T-case gears.
UPDATE:
What does it cost to regear an axle?
For a standard D-30/D-44 or D-30/8.25 combo, you should count on spending $500 in parts for both axles. For that money you should get: a set of high quality ring and pinions (Spicer, Precision, US gear, Richmond, Yukon's premium brand) and a master install kit that includes 4 bearings (2 carrier/2pinion), carrier shims, pinion shims, an oil slinger, oil retainer, axle tube seals (front axles), pinion seal, and new ring gear bolts. You'll also get marking compound, Loctite, and a little brush. There is some additional stuff you may want to order for your axle while you have it apart, namely, wheels bearings and outer seals for your rear axle. This usually runs about $40 a side for a non-C-clip and $30 for a C-clip axle. If you are going from 3.55's to somthing in the 4's, generally speaking, you will need a new carrier, unless you are getting a full case locker (why wouldn't you?). Expect to pay $50 for a new, open case.
Labor costs vary dramatically depending on where you live and the competance/incompetance of the installer. Generally, it is much cheaper for you to pull the axle housings out of your Jeep, clean them up a bit and take them to your local, professional installer. If you do this, you should expect to pay about $200 an axle. For axles that are under a vehicle, I would expect to pay about $100-$200 more. Axle guys (me included) despise setting up gears under a rig.
What if I do lots of highway driving?
The above gearing recommendations are given for a rig that is driven on the highway at speeds of up to 80 MPH. There is only one tire size that I could see having some confusion. A 32" tire could probably get away with running a 4.10 gear on the highway, and still feel OK offroad. I think you'd be better off with a 4.56 gear, especially if you live in a state with a single hill. If you live in a flat place, or spend a lot of time at high speed, the 4.10s would likely net you better mileage.
Gearing is a subjective issue. A guy who lives in Florida may have different preferences than a guy in Arizona. Yet, there are general rules which apply, based on a lifted XJ with an overdrive transmission. In GENERAL, on a 4.0 that is in good condition, you want to keep the revs at or below 3,000 at max cruising speed. As an example, I've made very good mileage at 2,750 with 35" tires (18 mpg). Don't be afraid to spin the little 4.0, as it is an undersquare motor, i.e. a short stroke motor. If you have the unfortunate experience of owning a 4 cylinder XJ or a V-6, disregard the following and go to 4.88's for any tire size larger than 30". So general gearing guide from your friends at URF:
30', 31's: 4.10 (don't do something stupid like I did and go to 3.73. Hey, I was a freshman in college at the time.)
32's, 33's: 4.56 (If you live in the mountains, or your rig is on a trailer a lot, put your purse down and go to 4.88's)
35's: 4.88's (Only because you can't get 5.13's in a Dana 30. If you live in a state that has a SINGLE rock you may one day want to climb, ditch the 30 and step up to a 44 and 5.13's)
37's: 5.38's will do you nicely, but your still going to want deep T-case gears.
UPDATE:
What does it cost to regear an axle?
For a standard D-30/D-44 or D-30/8.25 combo, you should count on spending $500 in parts for both axles. For that money you should get: a set of high quality ring and pinions (Spicer, Precision, US gear, Richmond, Yukon's premium brand) and a master install kit that includes 4 bearings (2 carrier/2pinion), carrier shims, pinion shims, an oil slinger, oil retainer, axle tube seals (front axles), pinion seal, and new ring gear bolts. You'll also get marking compound, Loctite, and a little brush. There is some additional stuff you may want to order for your axle while you have it apart, namely, wheels bearings and outer seals for your rear axle. This usually runs about $40 a side for a non-C-clip and $30 for a C-clip axle. If you are going from 3.55's to somthing in the 4's, generally speaking, you will need a new carrier, unless you are getting a full case locker (why wouldn't you?). Expect to pay $50 for a new, open case.
Labor costs vary dramatically depending on where you live and the competance/incompetance of the installer. Generally, it is much cheaper for you to pull the axle housings out of your Jeep, clean them up a bit and take them to your local, professional installer. If you do this, you should expect to pay about $200 an axle. For axles that are under a vehicle, I would expect to pay about $100-$200 more. Axle guys (me included) despise setting up gears under a rig.
What if I do lots of highway driving?
The above gearing recommendations are given for a rig that is driven on the highway at speeds of up to 80 MPH. There is only one tire size that I could see having some confusion. A 32" tire could probably get away with running a 4.10 gear on the highway, and still feel OK offroad. I think you'd be better off with a 4.56 gear, especially if you live in a state with a single hill. If you live in a flat place, or spend a lot of time at high speed, the 4.10s would likely net you better mileage.
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so you can view the plethora of hidden Tech Articles, which by the way, is extremely dated?
