Strange noise Limited Slip Differential

[RickMar]

Hello,
Thank you for taking the time to read this post.
I have a 1999 Mercury Mountaineer 5.0L with "D4" limited slip differential.

I replaced the front "DANA" shaft in December of this year @170,000 miles.

5,000 miles later I started to notice this "strange" crunching/binding noise when I started from a dead stop with my wheels turned in both drive and reverse. When I got going straight the noise went away. One day I stuck my head out the window to see what I could hear. It sounded like crunching/binding /rubbing sound at the rear tires. There is absolutely a noticable area where the noise goes away and repeats. The only way I can describe the noise is like "gritting your teeth" or when the "brake pads have worn down to bare metal" and the vehicle finally comes to a stop digging into the rotor. Or when the caliphers on disc brakes do not release completely and finally do.
The noise is absolutely without a doubt coming from the differential. I thought it possibly was a transfer case problem at the beginning but it is not.
All of the tires are the same size and brand.
Could one of you "Pro's" fill me in on what you think the problem might be?
Any information will be very much appreciated.
Thank you.

Rick

 

[IZwack]

Pop the diff cover and inspect the spider gears.

 

[RickMar]

Thank you IZwack for the info... I appreciate it very much.
When I was young ......a loooonnnngggg time ago, I did just about everything that needed to be fixed on a vehicle.
The one thing I never fiddled with were automatic transmissions or differentials.

I have been thinking of popping off that cover and see what the fluid looked like too. I have heard if this additive from AMSoil "Slip Stop" or something like that....I will have to snoop around and try to find a place to purchase it.

Take care...
Rick

 

[IZwack]

You could be onto something, maybe the fluid is just so old that the "friction modified" addivitive have deteriorated and the LS unit is chattering. But again, remove the diff cover and inspect just to make sure. And then refill with gear oil plus the "friction modifier" fluid (available from the dealer, its like $7 i think).