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Unread 04-08-2009, 05:00 PM   #1
corbin9191
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can you have two different gear ratios?

I have heard from people that you have to have the same gear ratio in the front as you do in the back axle. Is this true or can you have different gear ratios from front to back? I just want to be make sure that what I am hearing is true. Thank you

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Unread 04-08-2009, 05:02 PM   #2
oteps
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Yes you need the same ratio front and rear. If not, while in 4X4 something will break.
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Unread 04-08-2009, 05:05 PM   #3
corbin9191
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Quote:
Originally Posted by oteps View Post
Yes you need the same ratio front and rear. If not, while in 4X4 something will break.
OK! that was all I needed Thank you
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Unread 04-08-2009, 05:31 PM   #4
YeepieJeepie
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It can be close though. 3.50 on one end and 3.55 on the other or 4.10 and 4.11 are acceptable.

I do know for a fact that 3.08 on the front and 3.50 in the rear will lead to a broken transfer case. Luckily transfer cases are really easy to rebuild on your workbench.
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Unread 04-08-2009, 08:23 PM   #5
badoosh27
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you can have them, just dont put it in 4WD. i have 3.07's in the front and 3.73's in the rear and it works just fine in 2WD
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Unread 04-08-2009, 10:04 PM   #6
shrewd
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I was reading an article today in one of the mags that said 1-2% difference was doable, as the extra stress it created was relatively minimal.
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Unread 04-09-2009, 11:35 AM   #7
jdarg
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There often is a slight difference actually...the front axle and rear axle may not have the same number of pinion/ring gear teeth but the ratio works out to be within a few hundreths, i.e. 4.10 and 4.11.
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Unread 04-09-2009, 01:17 PM   #8
scout80xj
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In 4 wheel drive on a highly tractive surface like DRY pavement (which has a high coefficent of friction) than you need the ratios front and rear to be within 2% (at the most) of each other. For example many factory trucks with the Dana 44 front/Dana 60 rear had 4.09's in front, and 4.10's in the rear in this is acceptable because they are within 2%. However...on a slippery surface with a low coefficent of friction such as Ice and mud you CAN get away with running two different ratios front/rear. But I would advise you to run ratios front/rear that are within 2% of each other If you drive in 4x4 alot.
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Unread 04-21-2012, 10:16 AM   #9
grandfan94
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what if u run different tire sizes?
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Unread 04-21-2012, 01:41 PM   #10
chainz
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than you have some math to do....lol
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Unread 04-21-2012, 02:36 PM   #11
halpeters
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Quote:
Originally Posted by grandfan94 View Post
what if u run different tire sizes?
This would be the only way....

Some of the racing 4x4 trucks do this to run different size tires front and rear.

Also, 4 wheel drive tractors with small wheels in the front, and large wheels in the rear do this...
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Unread 04-22-2012, 06:44 AM   #12
grandfan94
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so would there be some fancy mathy way to find out the tire sizes, or just a simple sh-t cross-multiply?
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Unread 05-27-2014, 04:01 PM   #13
Thrasymachus
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Anyone know what the symptoms would be if there were different gear ratio's? My rear diff blew up so I had a locker and 4.56's installed. Also bought a TJ D30 with open diff and 4.56's. I swear that I recalled looking on the ring gear and saw "4.56" stamped/etched. When I let off the gas in 4wd (in neutral, with the clutch in) it has a noticeable deceleration/braking sensation... and I think the body is squatting. When I try to rationalize this if the front has a higher gear set, the front would try to pull away from the rear causing the body to squat. Vise versa if the front had a lower gear set the rear axle would be pushing into it and cause the body height to rise. This issue goes away when it is out of 4wd. I think I have already answered my own question... Just want others two cents?
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Unread 05-27-2014, 04:23 PM   #14
biffgnar
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Quote:
Originally Posted by Thrasymachus View Post
Anyone know what the symptoms would be if there were different gear ratio's? My rear diff blew up so I had a locker and 4.56's installed. Also bought a TJ D30 with open diff and 4.56's. I swear that I recalled looking on the ring gear and saw "4.56" stamped/etched. When I let off the gas in 4wd (in neutral, with the clutch in) it has a noticeable deceleration/braking sensation... and I think the body is squatting. When I try to rationalize this if the front has a higher gear set, the front would try to pull away from the rear causing the body to squat. Vise versa if the front had a lower gear set the rear axle would be pushing into it and cause the body height to rise. This issue goes away when it is out of 4wd. I think I have already answered my own question... Just want others two cents?
It's not going to be subtle if you have a mismatch. If you are debating nuances you don't have a mismatch.
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