My 3.55 LS rear has a humming noise. It occurs when I'm coasting through a right turn. Any ideas?

 

If it is the rear, could be pinion or carrier bearings, possible low on oil. could also be outer axle bearings, tires? usually when going through a turn it is a outer axle bearing. Just had my explorer start making a bad hum but it was at almost all speeds and it didnt change on turns----it turned out to be a bad pinion bearing. Check your oil for small metal particles--thats what the explorer had. If you have any of the diff bearings replaced it would be good to replace them all. Also check your u joints.

 

How did you determine the pinion bearing was bad? Who replaced it and how much?

 

if it dont happen going in a straight line down the road a t 60 MPH it normally is not the bearings, they whine all the time NORMALLY. if it only happens when you turn, that is normally related to the LS unit. it could have some internal wear, or might just need more friction modifier. i would drain and refill with 75w140 synthetic gear lube and add a tube of the friction modifier and see what happens. Auto Zone sells a 7 oz tube of the friction modifier for $6. put it all in.

 

I narrowed the area of the noise to the diff.----I found the metal shavings in the oil---there was a service buletine out on bad explorer pinion bearings. I brought it to the shop and they removed and took apart the diff. and they found the bad bearings, the pinion and carrier bearings were all going bad---probably the shavings from one ruined the others. It cost around $780 for bearing replacement and R+R (complete job). Narrowing down where the noise is coming from is most important and if there is metal in the oil that is the final give-away.--------------------------A LIMITED SLIP that is going bad will chatter going around a turn (left or right). A hum going around a turn is usually a outer axle bearing---if it hums when you are turning right than the left bearing is probably going bad. (the one with the load on it).

 

Sounds like drianing and refilling would be a good first step. If it doesn't go away, I'll take a look at the bearings.

 

If there is fine metal bits in the oil there would be no sense going any farther, it would be time for the rebuild. Did You rule out outer axle bearing?

 

If there is fine metal bits in the oil there would be no sense going any farther, it would be time for the rebuild or replace. Did You rule out outer axle bearing?

 

I haven't ruled out the outer bearing. In fact, my gut tells me that's the problem. Gotta do the easy stuff first. Step 1: Post on FTE, make sure you're not just throwing parts at the problem.

If the fluid level is good, I'll pop the cover. If everything looks good there, it's probably bearing time. What are the odds of a U-joint causing this?

 

The outer bearing is what it always sounded like to me. A bad u joint will make a rumble sound and vibration and is usually worse when decelerating/accelerating, but they need to be checked.