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  #16  
Old February 21st, 2017, 08:26
trippled trippled is offline
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Re: '98 XJ on 33s

Best way to check is pull the diff cover and check the ring gear. It should have two numbers corresponding to the tooth count. 41 and 10 would a 4.10 set, for example.
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  #17  
Old February 21st, 2017, 11:56
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GordoSmasho GordoSmasho is offline
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'98 XJ on 33s

Having commuted for many years with a stick and 33s I would definitely suggest 4.56. With a manual regearing won't really help your crawling ability. You need deeper tcase gears for that. Regearing for a manual is mostly for driving pleasure. You will never regret doing 4.56. You can set the cruise control and just smile as it climbs up just about every hill on the highway, without downshifting, even fully loaded for camping. I got a fairly solid 17mpg commuting in traffic with 500lbs of tools and ladders onboard.
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  #18  
Old February 21st, 2017, 14:15
FloydXJ FloydXJ is offline
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Re: '98 XJ on 33s

For the gears, you could count driveshaft rotations if you don't want to pull the cover. Lift just one rear tire off the ground. Mark the driveshaft and count rotations as the tire is manually turned one complete rotation. The spider gears will make the ds go double time, so divide the rotations in half. 6 ds rotations is 3.07, 7 is 3.55, 8 is 4.10 etc. Not as accurate as counting teeth, but gets you an idea.
As for gearing, go 4.56. That said, I have 3.55, 35s. 5-5.5 of lift and a stick and I use 5th gear all the time. 2000 rpm at 70mph and get 15 city and 17-20 hwy. 230 to 300 miles per tank of gas depending on the mix. weighs around 5200 pounds and has zero engine mods. It doesn't seem like there is a way to predict mpg with a regear, as results are widely varying.
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  #19  
Old February 21st, 2017, 14:18
Murray_XJ Murray_XJ is offline
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Re: '98 XJ on 33s

Thanks again everyone for the detailed responses with personal experiences... I appreciate it!!

First step... i.d. what is currently in it. Cheers!!
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  #20  
Old February 21st, 2017, 15:02
FloydXJ FloydXJ is offline
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Re: '98 XJ on 33s

For the gears, you could count driveshaft rotations if you don't want to pull the cover. Lift just one rear tire off the ground. Mark the driveshaft and count rotations as the tire is manually turned. The spider gears will cut the ds revolutions in half. So turn the tire 10 times, and divide the turns of the ds by 5. Or whatever equation works best for you. The more turns of the tire you do, the easier you should be able to see different ratios. This is easiest with two people. Not as accurate as counting teeth, but can get you close. As for gearing, go 4.56. That said, I have 3.55, 35s. 5-5.5 of lift and a stick and I use 5th gear all the time. 2000 rpm at 70mph and get 15 city and 17-20 hwy. 230 to 300 miles per tank of gas depending on the mix. weighs around 5200 pounds and has zero engine mods. It doesn't seem like there is a way to predict mpg with a regear, as results are widely varying.

Edited that previous post. Use this version if you are going to count drive shaft revolutions to find your ratio.
Got a very important fact backwards the first time. Must have been all that crack I smoke.

Last edited by FloydXJ; February 21st, 2017 at 15:06.
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  #21  
Old February 21st, 2017, 19:07
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GordoSmasho GordoSmasho is offline
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'98 XJ on 33s

The numbers that people are quoting for rpms at a given speed are a bit off here. A simple gear calculator will give you a proper rpm calculation.

http://www.grimmjeeper.com/gears.html

You should be aiming for 2100-2600 at your most common cruising speed. That is where you will tend to get the best driving ability and mileage. That is where the meat of the torque ban is. That applies to auto and manual trans. Toward the 2100 for more flat land cruising. More toward the 2600 for more hauling capability and mountain country. There is no hard fast rule but those are good guidelines for a lifted jeep with larger than stock tires.
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  #22  
Old February 22nd, 2017, 13:23
FloydXJ FloydXJ is offline
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Re: '98 XJ on 33s

Quote:
Originally Posted by GordoSmasho View Post
The numbers that people are quoting for rpms at a given speed are a bit off here. A simple gear calculator will give you a proper rpm calculation.

http://www.grimmjeeper.com/gears.html

You should be aiming for 2100-2600 at your most common cruising speed. That is where you will tend to get the best driving ability and mileage. That is where the meat of the torque ban is. That applies to auto and manual trans. Toward the 2100 for more flat land cruising. More toward the 2600 for more hauling capability and mountain country. There is no hard fast rule but those are good guidelines for a lifted jeep with larger than stock tires.
If using the calculator, be sure to measure your tire height. Mine are 35s, but between being km2's and having 50000 miles on them, they measure 33. And inputting 33 puts the calculator pretty close to my GPS verified speeds.
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