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changing the differential fluid

29K views 17 replies 9 participants last post by  OsirisGuy 
#1 ·
This seems pretty straight forward but I just want to make sure I have everything to do it. I know I'll need 3.75 pints of gear oil and I'll also need friction modifier. To reseal the diff is there a gasket or do I just use silicon? For that matter any specific silicon? Also can this be done without lifting the car? I could drive the car in reverse up onto ramps but I would think I would want the car to be level. Thanks.
 
#2 ·
Make sure you get the right weight oil (I cant remember right off.) Have the car level and up in the air enough to work under it. Then remove the rear cover and let the oil drain out. Once done wipe the bonding surface for the rear cover very good to help ensure a good seal. You can buy rear seals but most simply use silicon to seal the rear end. Put a good amount of silicon on the rear cover making sure to go around the inside and outside of the bolt holes on the cover. Carefully place it on the rear housing and bolt it down evenly. After you have all this done remove the fill plug located on the front of the housing and squeeze the lube into it. It can be hard to get to but you should be able to maneuver it if the rear end is hanging free while the car is jacked up.

You only need friction modifier if you have a traction lock or other positive traction style device if my memory serves me right.
 
#3 ·
Thanks, Spec. I'm doing this on the GT so I do need the friction modifier. Does anyone know if I could just use Royal Purple 75W140 (that's the correct weight) Max-Gear oil instead of regular gear oil + the modifier? According to royal purple "All viscosities of Max-Gear are formulated with hypoid friction modifiers necessary for use in clutch or cone type differentials. No additional additives are necessary."
 
#4 ·
You can buy many brands of oil for the rear end that already contain friction modifier. I would just buy OEM fluid or the Royal Purple brand without it and add my own unless the amounts are enough to meet the specifications needed for the 8.8 inch rear end.
 
#8 ·
Royal Purple FTW! besides, it already has a friction modifier.

i just used a nice thick bead of RTV to reseal the case. i let it sit for a hour or two for the rtv to setup after i bolted the cover back down before i added in the gear oil. no leaks after ~6 months.

btw get a foot of vacuum/fuel hose thats the right size to fit over the nozzle of the bottle, and it makes filling up the diff 100x easier. you can just hold the bottle way up in the chassis and let it drain down by itself and just hang out while it does so.
 
#9 ·
While the cover is off you can replace it with one that has a drain plug and make the change much easier next time.
 
#13 ·
Ford Service Workshop Manual said:
Fill the rear axle to the level shown, approximately 1.66-1.77-liters (3.5-3.75-pints) of lubricant, and install the filler plug.
Use SAE 75W-140 High Performance Rear Axle Lubricant F1TZ-19580-B or equivalent meeting Ford specification WSL-M2C192-A.
And my little "manual" that came with the car said the same. Maybe they changed the spec when they went to the 3650 transmission.
 
#17 ·
You "should" be able to get to it by just dropping the exhaust, but, a couple of the bolts might be a beast to get to on the back of the IRS cradle. When I resealed mine, I had the entire IRS out of the car....so I just took the chunk out and messed around with it.
 
#18 ·
Closing this thread as it is three years old.

Mustang Mafia - try starting a new thread. New threads are perfectly fine and you will get a better response.

And I would think Spector figured out by now :D
 
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