<hr style="color: rgb(209, 209, 225); background-color: rgb(209, 209, 225);" size="1"> <!-- / icon and title --> <!-- message --> <!-- BEGIN TEMPLATE: ad_showthread_firstpost_start --> <!-- END TEMPLATE: ad_showthread_firstpost_start --> The rear on my truck has been leaking oil around the rear diff cover for awhile, so I want to pull the cover off, replace the gasket, and put in new oil.

So, I have a couple questions, namely:
1. What weight oil, and can I go synthetic?
2. How much oil does it take?
3. What friction modifier do I need, and how much? (truck had a trak-lok)

BTW on these ones is it better to use silicone on the diff cover, or a regular paper gasket?

 

Your axle came with synthetic......

Approximate Lubricant Capacity (In-Vehicle Repair)(a) (b)
Vehicle F-250, F-350 Regular & Chassis CAB, F-250/350 H.D.

Axle 10.25-Inch Ring Gear

U.S. Pints 6.5(c) (d)

Imperial Pints 5.4

Liters 3.0

(a) - Ford design conventional axles use Rear Axle Lubricant XY-90-QL or -KL (ESP-M2C154-A) or equivalent.
(b) - Service refill capacities are determined by filling the axle with the specified lubricant to the bottom of the filler hole with the vehicle in running position.
(c) - Plus 8 oz. (U.S. measure) additive friction modifier, C8AZ-19B546-A (EST-M2C118-A) or equivalent for limited-slip applications.
(d) - Rear axle lube quantities must be replaced every 100,000 miles (160 000 km) or if the axle has been submerged in water. Otherwise, the lube should not be checked or changed unless a leak is suspected or repair required.
Note: 6.5 pints of lubricant is the fill specification when the axle is installed in the vehicle. If the axle is out of the vehicle, fill with 7.5 pints of specified lubricant.

 

What the hell is XY-90-QL? Any idea what weight that is?

 

i searched here and when i did mine i used syntheic blend 80-90wt also if you have limited slip add the friction modifier. i think mine was 3 qts maybe a little more