Gear lube question

[Juggernaut]

I did a search but couldn't find what I needed.

Can anyone tell me what weight oil goes in the 8.8 rear and how much?

Thanks,
Randy

[bobcowan]

Gear oil is a lot like motor oil. If you're beating on it pretty hard, you should use something heavy, like 85W-140. But if you're using it lightly, a lighter oil will work better, like 75W-90. It takes about 3 pints. Get two 1 qt bottles and you'll have plenty for the diff, and some left over to pour on your shirt while you're laying under there.

If you have limited slip, don't forget the additive.

[Hal Copple]

I just did mine the other day. I use synthetic Mobile I in the 75/90 wt. The "easy" way for me is to remove the fill plug, get some 1/2 inch plastic tubing from Home Depot or other, then with the passenger wheel off, raise the tubing up alongside the car, then squirt it in using the plastic bottles it comes in. It takes just under three quarts.

As for draining the old fluid, that can be a chore. Run the car until it is hot, then you can suction it out via the fill hole, getting most of it, or on my car, when my diff cover was off once, i had an AN 4 fitting welded in, so i can uncap it, and drain it out easily.

Just got back from the beach, came back in the rain, 220 miles, was down near Charleston for the Holiday. Cruised about 85, except when traffic was bogged down.

Pulled in for gas along the Interstate, this man wanted to take some pictures of my car, so I had him stand by it, and shot several with his digital camera. This sort of thing happens a lot with these cars.

all the best,

[Juggernaut]

Thanks for the input guys, I'll get the 75/90 weight & some tubing from Lowes.

Bob - I'm not sure if it is a limited slip, think it is though. What additive do you mean?

Hal - Sounds like you had an interesting trip! Yep, I bet these cars get a lot of attention!

Thanks again,
Randy

[SantaFe66]

Hal,

Where did you get the AN-4 fitting? I'm going to do the same thing this winter when I change the gears.

I've been using Royal Purple 75W90 Synthetic in my street-driven 9" and haven't yet put the limited slip additive in (not sure what I would solve by adding it). I'm pretty happy with Royal Purple and assume any synthetic like Mobil 1 or Amsoil gear lube would work, as long as the requirement is for API GL-4 or GL-5. Since I have floating axles and tube seals, my capacity is just short of a gallon.

What kind of limited-slip lube is used by those that add it?

Paul

[Barnsnake]

It's called a "Friction Modifier". Without it you may get groaning or popping noises during low speed turns.

[Bob In Ct]

Randy:
Jack up the back of the car. By hand (in neutral) turn one of the tires. If the other side turns in the same direction it's a limited slip and you need the modifier. Put the modifier in first, then fill until it overflows. Use the 75w-90.

Hal, It's Mobil1.

Bob

[Juggernaut]

Originally Posted by Bob In Ct

Randy:
Jack up the back of the car. By hand (in neutral) turn one of the tires. If the other side turns in the same direction it's a limited slip and you need the modifier. Put the modifier in first, then fill until it overflows. Use the 75w-90.

Hal, It's Mobil1.

Bob

Thanks for the info Bob. I know what I need to get now.

Randy

[Hal Copple]

you can get steel or aluminum NPT/AN fittings, then an AN 4 cap, at just about any online race supply place. Be sure you know if your rear end cover is steel or aluminum, so you can properly have it drilled then welded with the matching metal.

I use Redline for my engine, BG Synchroshift II in my Tremec, and Mobil 1 in my diff. Castrol SRF in the brakes, and Valvoline Synthetic brake fluid (not silicone) in the clutch fluid. Use a huge NASCAR no-bypass oil filter, on a mount from Ernie Elliot, off of one of the Evernham Dodge cars. Expensive, come sealed to avoid tampering.

I change them often. Works for me, over the past 120+ thousand miles, including over 3000 track miles.

By the way, it will use a quart of oil in about 100 track miles, but goes about 900-1000+ miles per quart on the street.

all the best,

[bobcowan]

If it's a solid axle, the proper way to drain the diff is to remove the cover. That's good, because it gives you the oppurtunity to sweep out all the small filings, and inspect the parts. Lots of vehicles are that way.

To put the cover on, just use your favorite silicone sealant. I cut the heads off a couple of bolts and cut a screwdriver slot in the end. I can screw them in to act as guide pins so the cover doesn't slide around while you're getting the other bolts in place.

If you have an IRS pumpkin, then a drain hole is a welcome addition. In many apps (like my FFR), the only way to remove the cover is to remove the diff. Kind of a pain, and very messy. I drilled a hole in bottom, tapped it for a 1/4" NPT, and installed an inexpensive brass plug.

The best friction modifier is from Ford. All the diff experts I've talked to over the years recommend that for every clutch type diff they rebuild.

[Michael P. Wole]

Friction modifier...is that what is referred to as "whale" oil??
Had a situation with my F350 dually.. when I backed up, felt like it was binding and made a clicking noise...Ford dealer put additive in and called it "whale" oil..problem went away..Have never experienced this with Ford 9" with lockers over the years. Guess putting the additive in would be a good idea tho.