Rear Differential Fluid Change

Spider

Registered User
i looked under my car and it looked like a pain to pull the cover off and put new gasket on and fill it up with new fluid.

can anyone help me with the removal process and refilling the gear oil please.
 
There should be a fill plug on the right side of the rear casing. So you'll need an oil suction devise (looks like a large diameter bicycle pump) to suck out most of the old fluid. You can gravity fill the diff. with 1qt bottles and a long hose, but it's a bit of a pain - so get one of the cheap plastic oil fill pumps that can be placed in a quart or preferably a 1/2 gallon container to fill it. Only takes like 3.1/4 pints. If you have a limited slip then you'll also need 2-4 ozs of friction modifier as well as the 75W90 oil. The oil sucker & pump are relatively inexpensive at most auto parts stores. If you are thinking about using synthetic fluid, I recall that Ford now uses 85w140 in all their diffs.
 
cool thanks for the help, i was told buy the main tewch at Royal Purple to use Royal Purple MaxGear 75W90. would i still need the 2-4 ozs of friction modifier ?
i have no idea what i have in the rear im pretty sure everything is just stock so whatever that may be im not sure.

im totoaly new to the back so in the pic is this the plug i drain and fill from ?
should i just take the fluid out or would it be good to take the cover off and replace the gasket to since my car has 175k miles on it.

thanks again for yout help :)
 
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The cover isn't that bad to remove. Four bolts (two vertical and two horizontal) hold the rear mount. After that, the cover can be removed for inspection. Pretty simple. All you need to be careful of is the vent tube spout is plastic and easily broken. It can be drilled out and replaced with a brass hose barb if you happen to break it. I use normal gear oil 85W90 and 1 bottle of ford friction modifier.
 
That looks like the right plug - it has a recessed square head, so you can normally use the square end of a 1/2" socket extension or an old fashioned diff. tool to open it (may need the tap from a hammer if it's never been off). As for the friction mod; most SC's came with a limited slip diff or "traction lock" - and there is normally a metal tag on one of the diff bolts. I believe (someone can confirm) that only the automatic 94/95 SC's with "traction assist" had open diffs. I'd check with Royal Purple because some oils like Redline & Richmond come with the mod already mixed in. I would also be cautious about using 75w90 synthetic as it kinda thin running (although the same weight) and may create some leaks like at the pinion seal - I believe that is why Ford now recommends a 75/80/90w140 when using synthetics in the diff. Personally I used Richmonds 85w/140 synthetic in my '93 and no leaks past 200,000m
Hope that helps.
 
I just recently did this whole process.......

75W140 Synthetic Gear lube.....2 bottles of Friction Modifier.....

Runs like a top!

I removed the entire Diff, so I was able to do the lube swap easy..just open and dump.....
 
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