Bside2234

I'm working on changing all my fluids on my new to me 1999 5.4L Lariat. Starting with the back differential fluid. I think it's a 9.75 differential and I think the gearing is 3.73. Door jamb sticker says B6 under Axle and I attached a few pics of the tags on the differential.

Now to the questions:
It is a 9.75 correct?
Is it limited Slip? I want to know if I need a friction modifier.
One tag says 5W140 Synthetic Oil only. Does this really mean 75W140?
How much fluid does the axle need/hold?
Sorry if these questions are asked a 100 times over or in some FAQ I missed. I'm just not familiar with the truck at all yet.

akdoggie

It uses 75w-140 synthetic fluid. It is Limited Slip, so yes it requires the XL3 modifier. It takes less than 2 quarts of fluid total.

(Rear Disc Brakes), 9.75" Ring Gear, 3.73 Ratio, ID V923A fits 2001 up.

Bside2234

Thank you!
Probably says on a bottle but how much XL3 per quart?

akdoggie

one bottle per rear end.

Bside2234

Thanks again.

danweasel

Hi,

Mine is a 3.73 limited slip (it's a 97 if that matters). Can you tell me what weight I should put in the rear and, while were at it, the front diffs? Where do you find this info? I know this questions is dumb, by the way...

Thanks,

Dan

ANT99F150

The rear should have a tag on it that says what weight to use but it should be 75w140. Your rear diff will also need the friction modifier as stated previously. The front takes 75w90.

blupupher

iTrader: (2)

Just be aware, this stuff smells something horrible.
And I mean horribly gross.
Wear gloves when handling, if you get it on your skin, it will stay on for days, no matter what you wash it with.
Ask me how I know.

I find it easiest to add about 1/2 a bottle of gear oil, add the XL3 to the bottle of gear oil, then finish adding it.

dontherogue

I had to replace the differential cover gasket on my '99 xl a couple of summers ago, and I will always remember how bad that fluid smelled. Good thing I was wearing my rattiest work clothes because I got some fluid on the shirt and pants and ended up throwing both in the trash. Crankcase oil, gas, diesel, tranny fluid - none of them smell anywhere near as foul as differential fluid. The only saving grace was that the gasket cost ten bucks and I was able to do the job myself. A service center I called insisted that the fluid needed to be replaced as well - with taxes the job would have been over two hundred bucks! As I recall, the owner's manual says the diff. fluid is 'lifetime' and so I believe I would have paid through the nose for unnecessary stuff.

Bside2234

Yeah, I've done it in my Jeep before and that is how I remember the whole experience. Bad smelling.