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Old 07-22-2013, 03:25 PM   #1
Join Date: Sep 2012
Location: Alexandria MN
Posts: 19
New rear end so change gears?

Hi guys I have a 1998 TJ with a 4.0, auto, 31-10.50-15 Duratracs, D30/D35 w/3.73 gears. Lockrite up front. I want to install an Detroit truetrac in the rear so I am wondering if I should bump up to 4.11's or not! My next tires will probably be 33-10.50's but that's a couple years away since I just put the DT's on.

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Old 07-22-2013, 03:59 PM   #2
Abe Froman

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Join Date: Feb 2010
Location: Was in the mountains, now in Texas
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A Dana 35 and a locked rear end is not a good idea. I would upgrade the rear end first to a Dana 44 so it can handle a locker without breaking. I locked a Dana 35 for a couple years, but I had chromolly axle shafts and always carried spares with me everywhere I went. Never had a problem, but it was always a concern in the back of my mind. Remember that when you regear that you will need to do both the front and the back. Oh yea if you have lockers in the front and back it will be a different vehicle in the ice and snow.

2000 Sahara, 3.5" Rubicon Express Lift, 1" spring spacer & 1" Body Lift, 33" or 35" BFG Mud tires, Front & Rear ARB, Rancho 9000 shocks, UCF Ultra High Belly Up, Savvy gas tank skid.

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Old 07-22-2013, 05:23 PM   #3
Join Date: Jul 2013
Location: Las Vegas
Posts: 77
I will give you the mathematical formula for tire roll out and you can decide what is best for you:

stock tire height in inches x 3.14 / gear ratio = stock roll out for factory performance (this is how many inches the Jeep moves forward for each turn of the drive shaft)

The closer that you stay to this number the more stock the Jeep will run, the more accurate the speedometer will be, etc...

use this formula for different tire heights and gear ratios. A lower than stock number will give more take off power, a higher number less take off.

Also remember that the higher the gear ratio the less gear contact. Which means that the more chance of breaking one of the gears.

Best of luck whatever you decide to do...
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Old 07-22-2013, 05:23 PM   #4
Join Date: Sep 2012
Location: Alexandria MN
Posts: 19
I don't think a Truetrac is a locker. I have read the post about the D35s limitations so I am going with a lsd for the rear. My question is about the gears that compliment my setup!
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Old 07-22-2013, 05:28 PM   #5
Join Date: Sep 2012
Location: Alexandria MN
Posts: 19
Thanks jsuggs!
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