Question Rear Axle Servicing

[troutwest66]

The owner's manual says the rear differential oil is a lifetime deal, only service if there's a leak or repairs done. I bought oil for the front diff. but I held off on the rear. What has everyone else done here? Leave it or change it out for new synthetic? My axle code is C1 so that is the LS if I remember right.

 

[DaveBen]

If you are having no problems, leave it. If your posi isn't engaging then you can change the oil and add a friction modifier.
FORD XL3 FRICTION MODIFIER ADDITIVE is available at your dealer.

 

[troutwest66]

No problems that I'm aware of. NAPA has the Valvoline Synthetic (proper SAE viscosity) and friction modifier (I don't remember the brand). Should I use Motorcraft only in the rear or is what NAPA has alright? Assuming I need to change it. At this point I'll probably just change the front to Valvoline 75-90 synthetic.

 

[DaveBen]

Other oils are fine. I have not used Valvoline gear oil but I have used other brands and they work good.

 

[Tbar]

I did mine after it crossed the 100k mark and used synthetic Amsoil.

 

[troutwest66]

I'll check it first. Has a plug on the driver's side of the housing like the old Sterlings, right?

 

[WD40]

I use synthetic Amsoil, have changed it twice already at 40,000 miles each, looks about the same as when I put it in there.
Doug

 

[john griffin]

I drilled and tapped a 1/2" npt in the bottom of the center section so I dont have to pull the cover for changes.I use Amsoil Severe Gear every 50k or so.You have to do the drill and tap with the cover off so as to not contaminate the internals with chips.

 

[DaveBen]

Is the cover pressed sheet metal? If so that would be very difficult as the factory has a metal bung they press in that is drilled. You could make one and weld it into the cover.

 

[john griffin]

Not the cover,the BOTTOM of the cast houseing.There is a round,flat spot where they used to put a drain plug.I guess it was to expensive to dril/tap a hole!They quit doing that in the late 80's.I have seen covers that have what you are talking about,but it was higher up and was at "fill level'.