Limited slip differential going south?

[Half-cocked]

'99 AWD Mountaineer, 165K miles, D4 axle code.

I replaced the fluid in my rear diff about a year ago when it started to shudder on accelerating from stop, while turning. I used the Mobil 1 synthetic stuff which I've read doesn't need the anti-friction fluid added.

It's still shuddering.

Any idea what this costs to fix? I called my local shop to get an idea of $$$, but they won't even tackle this kind of job. They suggested I take it to a transmission shop, which I'm sure won't be cheap.

 

[SoNic67]

Well, of course is not cheap, is not like changing the oil...
Repairing it is not that easy, it requires some know-how and tools, that's why they directed you to the transmission shop.
https://www.youtube.com/watch?v=9I5gQVXVfs8

 

[radman]

Are you doing it yourself?

'99 AWD Mountaineer, 165K miles, D4 axle code.

I replaced the fluid in my rear diff about a year ago when it started to shudder on accelerating from stop, while turning. I used the Mobil 1 synthetic stuff which I've read doesn't need the anti-friction fluid added.

It's still shuddering.

Any idea what this costs to fix? I called my local shop to get an idea of $$$, but they won't even tackle this kind of job. They suggested I take it to a transmission shop, which I'm sure won't be cheap.

The first thing I would do is install a bottle of Ford C8AZ-19B546-A XL3 friction modifier or the Motorcraft equivalent at about $8 it is worth a try. If that does not improve your problem then it would be a mechanical issue. The cheapest fix would be worn clutch plates that run about $60-$90 for the parts. Beyond that the labor could easily run a couple hundred dollars although the dealers can charge as high as $600-$700 for a complete rebuild. Doing it yourself maybe $110 with new lube.

Mike

 

[bill06447]

It shudders because it's not slipping as it should (hence the need for friction modifier). Change the oil again, this time add the friction modifier (yes it's necessary even with synthetic).

Bill

 

[koda2000]

Put in a bottle of bottle of Ford C8AZ-19B546-A XL3 LSD additive $8-$10.

 

[colintrax]

It shudders because it's not slipping as it should (hence the need for friction modifier). Change the oil again, this time add the friction modifier (yes it's necessary even with synthetic).

Bill

No need to change the oil again. Just add the friction modifier

 

[SoNic67]

Correct, just add the FM in what you have now. I assume you filled to the top hole, so you might have to drain some fluid out before you add the FM.

True, Mobil1 comes with FM in it, but if your friction plates are worn, you might need more than what is stock in Mobil1.

However IMO is just a temporary Band-Aid. The friction plates surfaces won't grow back by magic.

 

[Half-cocked]

Thanks everyone. I'll add the friction modifier first, and see how that goes.