Rear Axle Seals

[KFH]

Had occasion to adjust the brakes on my FC.  While doing this I noticed some diff oil on the outside of the backing plates.  I removed the axle and found a reasonable amount of oil on the outer side of the seals, both sides were the same.  When I rebuilt the car I fitted new seals seals from CBC with the size that came from their listing for FE/FC.  These have been in for around 3500 miles.

A while ago I fitted a 3.55 diff and used different axles with new bearings and left the original seals.  The axles had a very minor score so I decided to fit Speedi sleeves over the location where the original seal ran ran n the diff where the axles came from.  Now after around 700 miles I have an oil leak on both sides.  It appears from markings on the axles that where the seals are running was not on the Speedi sleeve.  I carefully measured the distance from the outer lip of the seal to the inner face where the bearing sits and then repositioned the sleeve further in to make sure the seal would run on it.  There was a difference on both sides of the vehicle.

Anyway I gave the car a 15 mile run and bugger me one side is leaking again.  One thing I noticed is that the sleeve is only .3" wide and as best as I can measure the distance between the inner and outer lip of the seal is close to .3"

I cannot recall if I had any problem with the original axles which only had a very light single marking on them and no sleeves.  The new seals appear to have a double lip on them. 

Has anybody had rear seals leaking or can anybody shed some light on this problem?   Faulty seals?  Is there a special type of seal to use?  Sorry for a long winded story.

Keith

[fcwrangler]

Keith, the only thing that comes to mind could be that the axles nicked the seal on the way in. I replaced rebuilt a rear end 5-6 years ago with new bearings, seals and gaskets and never had a problem. The same rear end has been sitting out of the car since I started my rebuild and is still dry.
Jim

[hsv-001]

Tend to agree .The leading edge of the sleeves may have caught the lip of the seal .Haydn

[Trevor_B]

Just a thought Keith but is the breather clear?

I have experienced a blocked breather which resulted in a pressure build up when the diff & oil heats up.
This may cause oil to be forced past the seals or past the gaskets.

Cheers,
Trevor_B

[ardiesse]

Keith,

Leaking rear axle oil seals are a recurring problem, just like timing case oil seals, rear main bearing oil seals, gearbox rear extension housing oil seals, and diff pinion oil seals.

A couple of stories to illustrate:

I have an HT which started to leak diff oil out into one of the brakes.  Initially I popped the half-shaft out and replaced the seal.  No improvement.  On second attempt I inspected the lip of the new seal for nicks, and it was good.  Then I inspected the surface of the axle shaft where the seal bears, and there was some minor rust pitting, only evident under magnification.  I put the whole axle shaft in my father's wood lathe.  Then I got stuck into the sealing surface with wet-and-dry until the pits were taken out, and then removed the sanding marks with progressively finer wet-and-dry, and finally cutting compound.  That stopped the leak.

My FX is prone to leaking rear axle oil seals.  They're leather, and they're 63 years old.  The sealing surface of the axle shafts is neither grooved nor pitted.  I don't want to replace the seals, because I'm not certain that new seals would seal any more effectively.  Instead, I found it imperative not to overfill the rear axle.  If there's too much oil in the diff, it leaks out the rear axle oil seals.  If the oil level is correct or low, it doesn't leak.

In short: keep the relief holes in the backing plates clear and free of gunk, so you don't get gear oil in your brakes; don't overfill the rear axle; and if the leak is "oily stain on the backing plate" rather than dripping, I'd suggest you live with it.

Rob

[KFH]

Thanks for all the replies.  I had a look at the relief valve today and all was clean as.  I decided I would wipe the oil that I saw dripping from the bottom of the backing plate yesterday.  What oil??  I could find no oil anywhere.  I pulled the brake hub off and found everything totally dry..  I can only assume that when I washed everything out with kero yesterday a small amount stayed between some flat surfaces that I could not get to dry fully and a short run let it run down to the bottom of the backing plate.  Here's hoping.  Time will tell.

Keith