Help!!! Differential fluid

I am trying to do a complete synthetics swap however in my owners manual and I have tried searching here i cant find it. What weight of oil do I use in the front and rear diffs? I have a 98 eddie bauer with the 4.10s and LS diff if that makes a difference any help would be greatly appreciated.

It's in the capacities and specs section of the owners manual.

Front 80w90

Rear LSD 75w140 synthetic and 4oz. friction modifier - some aftermarket synth gear oils already have the friction modifier and may not need any extra added. If it chatters on turns it needs friction modifier.

Front axle fluid
Motorcraft SAE 80W90 Axle Lubricant
1.7L (3.5 pints)

Vehicles with conventional axles
Rear axle fluid *(1, 2, 3, 4)
Motorcraft SAE 80W90 Axle Lubricant
2.9-3.1L (5.50-5.80 pints)

limited slip differential.
Motorcraft SAE 75W140 High
Performance Synthetic Rear Axle Lubricant
Refer to footnotes
*2 and 3

*1 Fill to 6 mm to 14.2 (1/4 inch to 9/16 inch) below bottom of fill hole.

*2 Vehicles equipped with 4.0L SOHC and 4.0L EI engines may have a
limited slip differential. If your vehicle is equipped with a limited slip differential, add 118 ml (4 oz.) of additive friction modifier
C8AZ-19B546-A, Ford specification EST-M2C118–A, for complete refill of
8.8 inch and 9.75 inch rear axles.

*3 Vehicles equipped with 4.0L SOHC or 4.0L EFI engines and 3.73 or
4.10 rear axle ratios or 5.0L engines require synthetic rear axle lubricant.
Rear axles containing synthetic lubricant are lubricated for life. These
lubricants are not to be checked or changed unless a leak is suspected,
service required or the axle assembly has been submerged in water. The
axle lubricant should be changed any time the axle has been submerged
in water. For Traction-Lok rear axles, add 118 ml (4 oz.) of additive
friction modifier C8AZ-19B546-A, Ford specification EST-M2C118–A,
whenever the lubricant is changed.

*4 Refer to your ‘‘Service Guide’’ for axle fluid change intervals.

Thank You very much i could not find this info anywhere in my manual. thanks again

You're welcome. If you would like the owners manual in Adobe pdf form get it at this link:
Dead Link Removed

I have a differential question. I did not see in my owners manual where it specified dino oil in the front diff. on my 97 Mountaineer and I put synthetic in it. Would it be ok to suck all the fluid possible out and refill with dino oil or does it need to be taken out and cleaned out thoroughly? Any help appreciated.

yellow coupe said:

I have a differential question. I did not see in my owners manual where it specified dino oil in the front diff. on my 97 Mountaineer and I put synthetic in it. Would it be ok to suck all the fluid possible out and refill with dino oil or does it need to be taken out and cleaned out thoroughly? Any help appreciated.

Click to expand...

Why change it? Synthetic is a premium gear oil.

is this the same for a 94 xlt?...

Synthetic is an improvement over "conventional", so no need to remove it.

Also, you don't need to keep 2 different gear oils around. You can use 75w140 in the front too, if you want.

Also, since someone will, or has asked it: You MUST use Mercon V (that's a 5), NOT Mercon III , in the (automatic)transmission, or you will damage it. You CAN use Mercon V in the transfer case, and power steering pump. The owners manual specified the old Dex/Merc fluid, simply because a those components do not require the chemical/frictional changes made to the Mercon V fluid, and B.) the old Dex/Merc stuff is cheaper. However, there is no harm in using the "better" fluid in those other components.

Additionally, any vehicle which specifies DOT3 brake fluid, can use DOT4 with no problem. It's simply a newer, better fluid (higher boiling point). NEVER use DOT5 unless specified by the vehicle manufacturer. That is silicone fluid. It is not compatible with non-silicone fluid. Even a few drops will contaminate your whole braking system.

This concludes automotive fluids 101.

I was looking into some measurements and came across a dumb question. When I find a level check none of the guys talk about the orientation of the vehicle. For the tranny I have found a service manual reference to a tool (looks like a level ??) that might be used for the tranny but what about the drip level of the other things such as the rear/front differential or the transfer case. Does anybody know of a point to check for level / tilt on the car for the level check for each of the other 4 units (front/Rear Diff, Transfer case and Tranny)? Is there a common point where you can level it for all fill checks?

All fluids should only be checked with the vehicle level. does that answer your q?

My driveway is slanted. I think I might use a level on the bottom of the tranny pan itself for that check but that makes the vehicle look somewhat un-level but I think the main goal is the tranny oil in the pan level. The transfer case is at a different slant also so I may try to level it for its check.