Humming when above 20mph AND on gas pedal

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Apr 5, 2021 | 09:42 PM

#16

awg

CF Veteran

Joined: Mar 2016

Posts: 3,816

Likes: 725

Year: 96

Model: Cherokee (XJ)

Engine: 4.0

Quote:

Originally Posted by Admiral

I greased the slip yoke when I did the Ujoints last week.

When I changed the rear diff oil there was water in it (oil was milky) which is why I'm leaning toward pinion bearing.

I'll probably place an order and try your suggestion anyway.

That was my first thought when I heard your symptom

It is something that should gradually get worse if you pay attention

run the vehicle on jackstands will usually allow you to detect a bad diff or wheel bearing

Sep 14, 2023 | 08:09 AM

#17

g-nut

Newbie

Joined: Sep 2023

Posts: 2

Likes: 0

From: Baldwin County, AL.

Quote:

Originally Posted by Admiral

I greased the slip yoke when I did the Ujoints last week.

When I changed the rear diff oil there was water in it (oil was milky) which is why I'm leaning toward pinion bearing.

I'll probably place an order and try your suggestion anyway.

I'm having what sounds like the same or similar issue with my 2020 GC.
Any updates? Did you correct the issue, get rid of the sound?

Sep 14, 2023 | 08:19 AM

#18

Admiral

Thread Starter

Newbie

Joined: Jan 2021

Posts: 17

Likes: 1

Model: Cherokee (XJ)

Quote:

Originally Posted by g-nut

I'm having what sounds like the same or similar issue with my 2020 GC.
Any updates? Did you correct the issue, get rid of the sound?

Yeah I ended up fixing it. Turns out the diff got water in it at somepoint in it's life before I owned it and completely screwed with the viscosity of the gear oil. It ended up destroying the bearings, but the ring gears were still okay. Solution for me was to rebuild diff with the exception of replacing the ring gears. Replaced all bearings and seals in there - my jeep had the Chrysler 8.25 in the rear. Now it runs just fine without any road noise.

I'm sure it's built significantly different in any modern GC or Cherokee but the principles are the same.