How to determine if rear differential is LSD or not

[BrianV]

I have rear end noises at speed that I thought was wheel bearings but I'm thinking it might be gear noise from the rear differential. I noticed the rear diff was slightly wet looking (on the bottom half of the pumpkin). I think that seal might be slightly off. I haven't noticed any drips in the spots where the car is parked for days at a time. I'm going to check the fluid level and I assume it probably needs a top-off. I want to know what diff I have so I can figure out what fluid to put in. It's a 2wd 98 V8 Mountaineer if that makes a difference.

Thanks

 

[BrooklynBay]

If you go to Ford Explorer Specs, there is a listing for axle codes. Here is that link: http://www.explorerforum.com/ntrprize/Axle.htm

 

[BrianV]

If you go to Ford Explorer Specs, there is a listing for axle codes. Here is that link: http://www.explorerforum.com/ntrprize/Axle.htm

I assume the code is stamped on the differential somewhere?

 

[rhyno]

I believe you can find it inside the drivers door jam as well.

 

[BrianV]

I believe you can find it inside the drivers door jam as well.

Thanks, will check it out.

 

[BrooklynBay]

Here is a very similar thread to this one: http://www.explorerforum.com/forums/showthread.php?t=154008

 

[badgett]

If it has a letter as part of the axle code inside the drivers door (D4) it is L/S. If it has 2 numbers (41)for example , it is not

 

[BrianV]

Ok I checked and it's a D4. That means I need to use some additive right?

 

[badgett]

Yes , You have the same axle as mine. A 373 L/S. If you use Royal Purple it says it has the additives in it already. To be on the safe side I would use regular gear oil and a good additive. But that's just me.

 

[BrianV]

Yes , You have the same axle as mine. A 373 L/S. If you use Royal Purple it says it has the additives in it already. To be on the safe side I would use regular gear oil and a good additive. But that's just me.

Is the oil 75/90?

 

[badgett]

75w140 plus 4oz. of additive. Got that info from a spec sheet. Don't know what the other guys use.

 

[BrianV]

75w140 plus 4oz. of additive. Got that info from a spec sheet. Don't know what the other guys use.

Yeah just searched and it appears 3 qts (or a little less) of 75/140 synthetic and on some synthetics you don't need the additive. I'll probably throw it in anyways. I'll probably go with Mobil-1 or whatever I can get my hands on locally. I think I can get RP as well.

 

[BrooklynBay]

Lucas makes good additives. I know Lubegard makes a lot of additives, but I don't know if they make anything for a differential. I would assume that they do, since they are OEM approved.

 

[BrianV]

Lucas makes good additives. I know Lubegard makes a lot of additives, but I don't know if they make anything for a differential. I would assume that they do, since they are OEM approved.

I'll check for Lubeguard, their tranny additive did wonders on my tranny.