i got my rear diff cover at auto zone for $37. its just a plain black stock aftermarket cover.
rockauto.com has them for $25 but they wanted $7.50 for shipping. i needed mine right away because mine was leaking so i just paid the extra $4.50 to get it the same day.i dont have the part# off hand but if you go on either website you can put in your year make and model and it will bring up the part for you truck.

 

I bought Valvoline Synpower 75-140 for the rear differential on my '03 F250. I think you have a different gear ratio from me - mine is the Sterling LS differential. I called the Valvoline folks and asked them whether I needed the additive. They said I needed half the amount called for by Ford as they have LS additive in their product. They said their product does not require additional additives for any other vehicles except Ford does need one bottle.

 

my 04's limited slip still works great...i have had 3 leaks in the axle...one in each side axle seal and one right where the drive shaft connects so lots of topping off...i can still spin both tires

 

Thanks for your response. Yes, I find the 12 bolt pattern covers fairly easily (and that is what AutoZone and others keep showing as a stock replacement for my make/model/year). But mine only has 10 bolts (none missing) and apparently the common Dana 60 10 bolt cover is too small. That is the only one I have found with 10 bolts in the same shape as what I have. This laying on a gravel driveway trying to work upside down underneath isn't the easiest. I will go over to my friends house and put it up on his lift and try to find the axle tag or get the code off the door sticker just to be sure. Thanks again for the fast response and I am sure I will figure out what I have and where to get a replacement.

 

i just looked it up and a rear dana 60 has 10 bolts on the cover. is it possible the rear end was changed in your truck? did you buy it new or used? You might want to look into that. if you bought the truck used and the rear end went on it before you got it its possible the previous owner put a junkyard danna 60 in there because its cheaper. just a thought
To make things a little easier take your spare tire out and it will give you a lot more room under there to work. You might even be able to sit under there with the spare out of there if your not to tall. I'm 6'3" so I couldn't but it still gave me a lot more room to work on it in my driveway. Good luck and when u get the cover let use know what kind of rear u have under there

 

Great info! Anybody no how many qts of fluid in the Sterling??
I will prob throw the LS additive in first.
Not sure how bad it is to overfill if I need it after the fact.

Thanks

 

6.9 pints (3 1/2 quarts)

 

I just did mine although its a 3.73LS. Use the synthetic rear gear oil the diffs especially on 3/4+ trucks have been known to go out from overheating caused by improper maintenance, or improper break in.

It's rare that Ford requires synthetic so I'd trust them in this case. The front diff is comparatively much cheaper so don't worry if you have a 4x4.

I used valvoline rear gear lube that had additive in it. (Most all synthetics will) I then put it in and drove in circles in various directions (figure eights) and did not hear any chatter. I also did it in 4x4 (in dirt) after the front diff and transfer case and again didn't hear/feel any chatter.

You can put in too much additive and it WILL render the Limited Slip useless. While the debates of LS longevity are ongoing I'd rather not make mine useless by trying to be safe as it still works and mine is a 2003. If you have chattering you will know it and can get some additive at the Ford dealer. I'd add 2oz at a time if you have previously put in fluid with the LS additive in it to make sure you don't go too far.

Futhermore, unless you are a dual rear wheel (I'm not too versed on them) you can get an 08+ rear wheel diff cover from Tousley or other Ford dealers. Its a direct bolt on and is aluminum with fins. Its been reported to be 30* cooler than the non-finned steel one. Mine was rusting so it was no brainer.

 

You wouldn't ruin your rear end if that's what you are wondering. The main reason Ford requires a synthetic gear lube is because it's supposed to be a lifetime fill. It's supposed to never need changing unless it gets water in it or you have to remove the cover for repairs.

 

Thanks Kd.Thats what I wanted to know.I have no problem with useing the Synth,just wondering why it's a"must".

 

I bought it used and now I am embarrassed to admit it but I can't count properly - there are actually 12 bolts on the rear diff cover. FWIW, there are 10 on the front diff cover but I did not discover this until we got the truck up on a lift. Amazing what a little working room and clear view can accomplish. The cover you suggested from Autozone is the right one and fits perfectly. I used 3-1/2 quarts of the Valvoline Synpower 75-140 which has the LS additive already (I didn't put in any additional LS additive). While we had it up on the lift I also did the brakes & rotors, replaced the rusted shocks with 4 KYB GR2, and put some new 265/75R16 Kenda Klever M/T sneakers on her. Overall it was a productive day and now I know my truck a little better. Thanks for the help!

 

I have yet to come across a non synthetic 75-140.

I used Amsoil Severe Gear because that is what a local place I had an account with stocked. I got a couple bottles of the Amsoil slip loc friction modifier also. I did not add modifier for the change. I drove the truck some to check for chatter from the LSD. I got some chatter when loaded so I added some friction modifier.

As for the stock LSD it is just that "limited". The one on my 04' works like it did from new but it does not have near enough "holding power" for my taste. Ford could do much better. I will admit though I am not a fan of clutch style diffs that wear and contaminate the oil as they do.

 

Ive posted about this before....Good read

https://www.ford-trucks.com/forums/1...lip-blues.html

 

You née to add the friction modifier definitely in limited slip. Valvoline SynPower LS has the friction additive in it. K Man's online has Motorcraft full synthetic for just under $17 per quart and friction modifier for $4.09

 

I swear by Amsoil Severe Gear for All Diff Oils.