Tire Size, Gear Ratio and Gear Oil

A

angrymuffin

New member
Currently I'm using 32" tires and have 3.21 gears. I'm trying to figure out the correct gear oil weight to use in my rear differential. When I bought the jeep it came with 29" tires and noticed a considerable drop in power when I switched to 32" tires but definitely still drivable. It almost feels as if I'm towing something all the time. Does this mean that I should use 75w140 in the rear differential or would using 80w90 still be ok?
 
OverlanderJK

OverlanderJK

Resident Smartass
angrymuffin said:
Currently I'm using 32" tires and have 3.21 gears. I'm trying to figure out the correct gear oil weight to use in my rear differential. When I bought the jeep it came with 29" tires and noticed a considerable drop in power when I switched to 32" tires but definitely still drivable. It almost feels as if I'm towing something all the time. Does this mean that I should use 75w140 in the rear differential or would using 80w90 still be ok?
Click to expand...

75w90 is stock gear oil. Changing to a different one won't give you any power back.

If you haven't programmed your speedometer for the larger tires then that is the reason it is sluggish. It shouldn't be that noticeable going from a 29 to a 32.
 
Canvas JK

Canvas JK

-
angrymuffin said:
Currently I'm using 32" tires and have 3.21 gears. I'm trying to figure out the correct gear oil weight to use in my rear differential. When I bought the jeep it came with 29" tires and noticed a considerable drop in power when I switched to 32" tires but definitely still drivable. It almost feels as if I'm towing something all the time. Does this mean that I should use 75w140 in the rear differential or would using 80w90 still be ok?
Click to expand...

If you have an automatic you will need to adjust your shift points as well.

Here is a write up on how to change your differential fluid. http://wayalife.com/showthread.php?...K-Wrangler-Differential-Fluid-Change-Write-Up
 
A

angrymuffin

New member
OverlanderJK said:
75w90 is stock gear oil. Changing to a different one won't give you any power back.

If you haven't programmed your speedometer for the larger tires then that is the reason it is sluggish. It shouldn't be that noticeable going from a 29 to a 32.
Click to expand...

How do I program the speedometer? Also the jeep is a manual.
 
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