Rear diff fluid capacity

[F350Peter]

What is the gear oil capacity for my rear diff? I can't seem to find the right info in my manual. It's an '02 F350 with the limited slip.

Thanks all,
Peter

[SmokeyWren]

You don't mention which F-350 you have, and it makes a difference.

If you have single rear wheels (SRW), then your Ford "Sterling" diff holds 6.9 pints of gear oil. But if you have dual rear wheels (DRW), then your Dana 80 rear end holds 8.3 pints.

Ford says to add friction modifier additive if you have limited slip. In one place they say 4 ounces, and in another place they say 8 ounces. I wouldn't add any until after you button it up with the fresh lube, drive several miles, and then do a figure-eight test on dry clean parking lot pavement. If you don't get the clatter/chatter/racket from the rear end during full-lock turns, then you don't need any friction modifier. If you do get the racket (caused by a tire dragging around a sharp turn instead of rolling), then I would add one ounce at a time and retest.

Too much friction modifier will turn your LS rear end into an open axle. So that's why I would add one ounce at a time instead of just dumping in the whole 4 or 8 ounces.

[F350Peter]

Sorry about that....it's a SRW with the Sterling diff. Does the 6.9 pint capacity include the extra ounces of the friction modifier, or is that in addition to the 6.9?
Thanks for the info!

[ikidd49]

[ QUOTE ]
You don't mention which F-350 you have, and it makes a difference.

If you have single rear wheels (SRW), then your Ford "Sterling" diff holds 6.9 pints of gear oil. But if you have dual rear wheels (DRW), then your Dana 80 rear end holds 8.3 pints.

Ford says to add friction modifier additive if you have limited slip. In one place they say 4 ounces, and in another place they say 8 ounces. I wouldn't add any until after you button it up with the fresh lube, drive several miles, and then do a figure-eight test on dry clean parking lot pavement. If you don't get the clatter/chatter/racket from the rear end during full-lock turns, then you don't need any friction modifier. If you do get the racket (caused by a tire dragging around a sharp turn instead of rolling), then I would add one ounce at a time and retest.

Too much friction modifier will turn your LS rear end into an open axle. So that's why I would add one ounce at a time instead of just dumping in the whole 4 or 8 ounces.

[/ QUOTE ]

Smokey is absolutely correct as usual...I added 4 oz of the modifier and now have the equivalent of an open.... [img]/ubbthreads/images/graemlins/eek.gif[/img]Had to use 4 hi to get out of DD's flat driveway last week with one wheel on ice [img]/ubbthreads/images/graemlins/eek.gif[/img]. Got a bit of seepage around the housing so may change it again and no additive this time.
Ian

[SmokeyWren]

[ QUOTE ]
Does the 6.9 pint capacity include the extra ounces of the friction modifier, or is that in addition to the 6.9?


[/ QUOTE ]

6.9 pints (3.3L) is the total capacity. I would pour in 3 quarts (or 3 liters if you're in Canada) then test it and determine if you need friction modifier. After you have the right amount of friction modifier mixed in and tested, then top it off with diff lube.