changing differential oil

[monterey1962]

This is regarding the '87 Cougar. I noticed a bit of a mess on the bottom of the diff. today. I was thinking of putting a new gasket on. It probably needs fresh oil, as well.

What oil should I use? How much? Should I use some Lucas treatment? Any tips or info is appreciated. I'm assuming it's an 8.8 rear end.

[Blaze86Vic]

Yes it is an 8.8 rear. Motorcraft gear oil is what's in mine. I forget which weight though, I keep thinkin 90 weight for some reason though.

[Lincolnmania]

it's either a 8.8 or a 7.5 rear changing the oil is the same
use some 80w90 and trac lock additive if it has one..........get some carb cleaner too........spray out the sludge while you have the cover off........it takes just over 2 qts of gear oil to fill it up, teh fill plug is on the front side of the unit on the ds next to the pinion flange.........get ready to smell one of the worst smells on teh planet lol
scott

[Blaze86Vic]

FYI, all 5.0L come with 8.8 rears. And gear oil is one rank smell.

[Lincolnmania]

FYI, all 5.0L come with 8.8 rears. And gear oil is one rank smell.

nope the mustang did not get the 8.8 till the mid 80's seen tons of fox chasis v8 cars with a 7.5" rear

[monterey1962]

This is a 2.73 open rear.

[Freshmeat]

And gear oil is one rank smell.

I've actually developed an appreciation for the smell.

Then again, I've had a few too many and called a really good friend of four years by teh wrong name...

[Ifixyawata]

Scott's got it right. The only Fox Chassis T-birds or Cougars that ever got an 8.8 from the factory were the '87 and '88 TurboCoupes and the '88 Cougar XR7. All others were measly 7.5's.

[Ifixyawata]

Oh, one other thing... monterey, did you make it over to Coolcats.net (THE resource for Fox T-birds and Cougars). Or did you get the www.foxtbirdcougarforums.com (currently it's down, hopefully only for a short while.)

[Lincolnmania]

yea def check out coolcats.......that dude is cool got the idea for the ho swap there when i asked him about it in a townie he sent me to the other site

sorry blaze thought i was correct.......i got alot of yrs on you mang......i was the idiot working at the lm dealer when this stuff was new......and you guys know i dont miss a thing, used to ask all sorts of questions about the new cars.......almost bought a leftover 88 cougar ls........somehow ended up with that same car in 1998 for 200 bucks.......hows that for luck guys?
scott

[Blaze86Vic]

NO APOLIGIZING!!!

[88grandmarq]

jack up the car, support with jack stands. remove the diff cover bolts and drain the gear oil in a catch pan. clean the cover and axle housing then apply a thin coat of silicone, re-install cover. remove the fill plug on the front side of the carrier (uses 3/8" square drive) fill with 80W-90 gear oil, you may want to consider a 75W-90 semi-sythetic or full synthetic because of the cold climate you are in. Buy a pump that screws into the top of the bottel and has hose on it, then pump the bottle into the fill hole.
I usually just fill it up untill oil comes out the fill hole.

[monterey1962]

Silicone? Is there an actual gasket for the rear end? How tight should the bolts be?

Btw, been to CoolCats.

[Blaze86Vic]

You can find an actual gasket, but it's not worth the cost.

I put a nice thick bead os silicone aroud it then I put the cover one, and bolted it down to about 1/16th of an inch from the surface. Then I let the silicone firm up for about 5-10 minutes. Then I tighten it all the way down. I then left the fill plug off and let the silicone harden for a good while. The only reason I let it harden is because when I drained my rear and the new 05 Mustang rear the excess silicone had disolved in the oil. I'm sure it has no effect what so ever, but for some reason it bothered me enough to try and prevent it.

[88grandmarq]

Ford has been using Silicone to seal the diff covers since the mid 80's. If it's good enough for the factory, its good enough for me.

the bolts should be snug.... 1 grunt on the grunt-O-meter