rear pinion oil leak
 

I recently replaced the driveshaft rear pinion yolk and rear pinion seal on my 1951 ford because of an oil leak. Everything was fine for a couple of months, now I've developed a leak coming from the pinion nut area which is totally different than before. Any advice will be greatly appreciated.

Re: rear pinion oil leak
 

I've just done some research on replacing the rear pinion seal and it seems that it is recommended that you apply a non hardening sealant to the spline to prevent oil from leaking up the spline and out the nut. Could this be my problem?

Re: rear pinion oil leak
 

Yes, it could, also check the vent, it can get clogged with dirt causing pressure buildup

Re: rear pinion oil leak
 

has anyone had this problem and used the suggestion to use non hardening sealer on the spline to keep the lube from reaching the pinion nut? Leakage up the spline would be completly independent of the yoke seal.

Re: rear pinion oil leak
 

Not very familiar with that rear axle, but on some axles, if you loosen the pinion nut it changes the pre-load on the pinion. You have to be very careful doing this and not messing the pre-load up. Again, I am NOT familiar with this axle, but might want to check with someone who is before you do to much with it.

Re: rear pinion oil leak
 

as far as I know the seal is behind the splines on the pinion shaft, so the only way gear oil can get to the splines is if the seal is bad, did you lube the seal lips before installing it, did you bend the seal lips in any way when installing, is it installed right with the seal lips pointing to the gear oil, was there a grove in the yoke, as a last measure you can remove the tension spring inside the lip of the seal, one end of the spring is pointed and screws into the other end of the spring, unwind the spring to get it apart, then cut about 1/4 inch off the big end of spring then wind the ends of the spring back together, reinstall in seal, you have now tightened the tension on the lip of the seal and should stop any further leaks

Re: rear pinion oil leak
 

The splined pinion shaft enters the yoke in the rear before the seal. The seal prevents leakage between the rear housing and the yoke. It appears that there is nothing to prevent lube from entering the splined shaft. At this point the only thing that prevents it from leaking out behind the nut is a steel washer. I'm I missing something here, It would not be the first or last time. I had a leak at pinion seal and replaced the seal and yoke being careful to align all parts as they were, and lubricate seal. Seal does not leak now but lube leaks from behind nut.
It has been suggested that I apply a non hardening sealer to the spline. Does this make sense.

Re: rear pinion oil leak
 

as I said before, the seal seals the yoke the only way for oil to get to the splines is if the seal isn't holding

Re: rear pinion oil leak
 

Billfish, it makes sense to me that it has to be leaking through the splines and that a sealant is about the only cure I can think of.

You said you replaced the yoke, I suppose it is possible that the spline teeth are slightly different on the replacement yoke. I'm not where I can look at the nut/washer/yoke assembly, but if the washer pushes up closely to the yoke, maybe just remove the nut and washer and pack something like #2 Permatex around the splines and let the washer help push and hold it around the splines. Clean well with brake cleaner before application.

Re: rear pinion oil leak
 

This is a cut away diagram of an F1 axle, but think it is the basic setup. The seal lip only seals the yoke. Fluid could get around the bearing and up through the spline on the pinion. Some sealant on the splines should solve it. I would guess (as stated above) that a change in yoke lead to the issue.

Re: rear pinion oil leak
 

Thanks J Serry
As you stated the seal is installed on the outer edge of the housing and only seals the yoke. The splined shaft enters the yoke before the seal as shown on the pictures. So the entrance of the splined shaft gets no protection from the seal.
I will put a non hardening sealer on the splines and see what happens. Has any one reading this had a similar problem?

Re: rear pinion oil leak
 

my book shows the rear pinion and it shows an oil slinger and gasket in front of the pinion bearing and behind the seal, maybe yours is missing the slinger

Re: rear pinion oil leak
 

Thanks for all the help I get on this site. I also googled ( oil leaking from rear differential pinion nut) and found that oil leakage is fairly common from this location and completely separate from the pinion seal. It is a good practice to apply RTV to the pinion spline and loctite to the nut while re-assembling.

Re: rear pinion oil leak
 

I have also heard of using a thick grease to seal. Had a 9 inch that I replaced the pinion seal on and got some seepage when done. I had planned to try the grease trick but it stopped after a few weeks. On the 9 inch at least it takes a bit of pressure to crush the collar and change preload so not a big deal to remove nut and replace seal.

Re: rear pinion oil leak
 

Billfish, Did applying rtv (Permatex) to the pinion splines stop your leak? If so, did you apply it to only the outer 1/3rd or did you apply it along the entire spline?

Did you have to use a puller to remove the old yoke?

I have to replace my seal and I did a trial run playing with a spare differential I had and the yoke slipped right off. I am thinking if a puller is needed that the fit between the yoke splines and pinion gear splines is tighter and may stop the oil from weeping up the spline.