As far contamination,when you take the cover off , you will possibly see @ the bottom of the cover a rust level, this usually means the truck sat for a long period of time. Defintely use a gasket, and on the drain plug use like a plumbers putty, thread paste or whatever to prevent a leak, I only say this cause when I did mine, I used nothing and it leaked, as you will see the factory used something as well. Good luck and dont forget to look for heavy metal particles, you should find some, but you should hope not a lot, look for the magnet.

 

Just looked at my rear diff. I found the metal tag. It says "Only use FEHP oil 75W-90 FEHP. What does FEHP stand for? I've never heard of that before?

 

From TSB 06-4-4............
AXLE FLUID REQUIREMENTS HAVE BEEN CHANGED. ALL VEHICLES BEING REPAIRED BY THIS TSB MUST HAVE REAR AXLE LUBE XY-75W140-QL INSTALLED, IN PLACE OF XY- 75W90-QFEHP. AS PART OF THIS REPAIR, CHECK AND REPLACE IF NECESSARY THE CURRENT XY-75W90-Q"FEHP" METAL TAG, WITH A NEW 75W140 TAG (F3TZ-4121-AA). ADDITIONALLY, REMOVE THE MULTI-COLORED LABEL WHICH IS LOCATED ON THE RIGHT SIDE AXLE TUBE, OR BLOCK OUT ANY/ALL "FEHP" OR "75W90" REFERENCES ON THE LABEL.

 

I changed the rear end oil in my 2000 f150 a year ago. After draining everything out, I used this special tool that mixes air with a little bit of gasoline for cleaning (you need an air compressor to use it). Is that hard on the seals. Would diesel fuel be better to use? It was an open gear rear end. So far, I have no leaks at all, but now the bearings are going out because you can move the drive shaft up and down a good amount just before it goes into the rear end. To fix that, do you have to pull the cover off and take everything out to get to it?

 

A bit of gas probably didn't hurt anything. A better cleaner to use is a solvent like Varsol.
To replace the pinion bearings you have to pretty much pull the whole rear end apart and you'll need some special tools like a press, torque wrench etc.
I'm all for guys working on their own trucks but replacing pinion bearings is something I'd recommend having someone experienced do.

 

So what is this reply about not using any cleaner inside the differential housing? How does it hurt it? I always use brake cleaner for a grease/oil cleaner, best stuff i've found, dries instantly.

 

I always use brake cleaner too but will flush the diff with solvent first if it's really dirty.

 

BlueOvalFitter:

Great tip on making sure that the plug will come out first.

There have been many of times that I have run into similar situations where if I would have checked one simple thing first I wouldn't be in dire straits in the end.

 

12 bolt differential cover has no gasket. They are hard to find. I used the black rtv silicone to make a seal, then waited for it to dry for several hours before filling the differential. At the dealer service, they do the same thing. If you do get a gasket, make sure it fits before taking the old one off.

How do I know this? Did it today. Had a small leak on the bottom of the cover. Went to get a gasket, got in a hurry and drained before looking at the fit. Called the local Ford house and was told to use the black rtv which I had.

 

I just changed my differential lube and put 3 quarts of 75w140 and 4 ounces friction modifier. The parts guy said I would only use a little over 2 1/2 quarts. What is the actual differential capacity? I don't have a manual to refer to. I stuck a piece of wire in the fill hole to see where the fluid was at and it is just shy of the fill hole. I was just wondering what the actual capacity is. I put a chrome cover on and maybe that changed the capacity. Thanks everyone.

 

What should be used to clean the cavity?

 

I just wipe everything out with a rag dipped in solvent or gasoline... some of the above posts, the guys use brake cleaner which evaporates and leaves no residue. ... see post 22.

 

and the new oil spec is 75 w 140 synthetic....... the original posts are 10 years old.

 

Should I take it for a drive before doing it?

 

I use a micro fiber towel to get the residual that is puddled up at the lowest part of the inside cavity. And, I NEVER use anything to clean the cavity or gears.