I have to replace one of the wheel seals so I am going back with mobil 1 75W140 from auto zone and the ford additive does every ford truck use this additive in the rear end and is mobil 1 good enough oil?

 

I got mobil 1 in mine too, excellent choice. Also you must use the additive.

 

You only need the friction modifier if you have limited slip

 

I do not think mine is limited slip, it has the 19 as the rear end code. Is this info. correct?

 

I have to replace the Differential Gasket/silicon as it is leaking. I know I have a H9 axel also my differential is a 3.55 Limited Slip. What I need help with is the differential a 9.75 or a 10.25. I ask as there is a difference on the amout of additive you need to put in 4 oz vs 8 oz. I have look at vin codes the codes on the door jam I do not or can not find out.

 

Axle Codes (LS=Limited Slip / Traction Lok):
F-150:
19 – 3.55 Non-LS

 

If you have the 5.4 engine, you have the 9.75" rear. The 4.6 and 4.2 are mated to the 8.8" rear.

And why do people keep getting so confused about the 'additive'? If you have a LS rear, just buy the gear lube labeled for a limited slip rear, it ALREADY HAS THE ADDITIVE IN IT! No need to 'add' anything! Just read the flippin' label, it's real easy. I've owned and been inside more than one LS rear axle, and I've never yet needed to buy or use any additive. If it's an LS rear, I buy the gear lube specified for LS. If it's an open rear, I buy the regular gear lube. Done deal.

 

Hey Rocky let me pull a rabbit out of my F150

I have the 5.4 so that means I have the 9.75 and the reason for asking the amount of "additive" to put is is the local part store only has the Gear Lube without the additive. So.... how much additive for the 9.75 will be needed? 4 oz or 8oz?

 

in my LS 9.75 rear i put mobil 1 full synthetic with 6 oz of additive

 

I just get the additive from the Ford parts counter and it's not very much, so must only be 4oz. Cost about $5.00.

I've added it right along with the Amsoil 75w140 lube I used a couple of times now and the LS has over 145,000 miles on it and it still grabs and works as it always has....

Mitch

 

I've hear from many folks using Mobil 1 gear lube that no friction modifier is needed for ltd slips (no clutch chatter what so ever). Amsoil says the same thing, but I've found I get a little chatter with the Amsoil lube, so I use 4oz in my 9.75 pumpkin.

What ever you use...do NOT use RTV silicone gasket sealer. Make CERTAIN you use ULTRA GREY or ULTRA BLACK gasket maker. Synthetic oil will attack and break down RTV resulting in a leaky cover and a mess inside (nice coating of sticky RTV all all over the gears and bearings).

 

Hey, guys, where do you find Mobil 1 75W140 ???? I have looked everywhere, O'Reilly's, Autozone, Advance, Napa, etc. They all have 75W90 ... but no 75W140 which is what my 9.75 calls for. I'm beginning to wonder if this stuff really exists. Mobil 1 website shows it is one of their products, but they don't help you get any. I'm ready to change rear end fluid, but can't find Mobil 1 75W140.

 

If you do not have limited slip, you do not need the additive. Save your money. If you do they say use 4 oz. (1 oz per quart) If it slips or chatters add another 4.

 

Earlier Post
I have to replace the Differential Gasket/silicon as it is leaking. I know I have a H9 axel also my differential is a 3.55 Limited Slip.

But Thanks for that info I need to use 2.5 Quarts of fluid so it looks like I need 4 oz additive.

Also I looked for the Moble 1 and like another post can not find it. O'Rielly's and Wally World (Wal-Mart) do carry the 75W140. O'Reilly's also carries the additive but not Wally World

 

I got mine at Auto Zone.