Bad Bearings= Hot rear axle?

92XJ 4.0, AW4, 242, 8.8 (97) 3.55's, worn out 32's, EZ locker, towing light load (>500 w/trailer) at normal highway speeds (55-70MPH)


Coming back from a long distance (550 mile) trip I did an undebody check and noticed that my rear axle was very hot to the touch (diff to center of the tubes) and was leaking slightly I went up front and found that the front was cool as a cucumber.

All fluids were checked before trip

Could this be a sign that the bearings have gone south and are heating the fluid? I towed a lot more for much longer distances w/ a D35 and no problems and could use the advice. My regear was planned for early feb, but it might get pushed up if there is a problem.

As Always, any and all help is appreciated and thanks in advance.


John

naw.. thats just friction from the gears.... the front (pinion) of the diff is probably cool cuz it gets the most airflow to cool it down....
you leaked fluid cuz the gear oil started to boil.. (break down)
it was doing this because you were towing that load...
your 35 never had this problem cuz you had towed things with it before.. the gears are broken in for towing loads...
the 8.8.. did it come off of a totaled explorer? if it did it mabye was never broken in thoroughly.... meaning there were parts of the gar teeth than had never touched before.. and when you towed your junk... they met and there was added friction.. more heat.. ect.. ect...
change that gear oil.... its probably has lots of little metallic shavings...

thats my guess....

Yes, change the gear oil. For towing, stock XJ axles require synthetic 85w-140 gear oil-- your 8.8 would benefit from the same treatment. Synthetic gear oil does two things: superior lubrication for less metal to metal contact = less wear, and resists breakdown from heat. Normally the synth will run at lest 20 degrees cooler.

Props for doing an underbody check after an on-road excursion. Slightly psychic are ya, John?
:repair: :cheers:

How hot? Could you hold your hand on it? Sounds like normal heat to me.

Rev

The rear axle is getting hotter than the front because it is under power. A percentage of the power is dissipated as heat. If you can get hold of an infra-red pyrometer. shoot the ends of the axle tubes, just behind the brake backing plates after running several highway miles. If one side is hotter than the other, say 10° to 20° or more, suspect the bearing.

as long as you can hold you hand comfortably on it. i would not be that concerened

Is this with ALL 4 wheels and tires on??


Rev