Drips from the Differential

[ChrisMinelli]

I was under the ‘52 Plymouth tonight working on the brakes and noticed a new drip from the differential.  I’m hoping it’s just old and needs attention and doesn’t have anything to do with me having the car up on jack stands for a few weeks and no weight on the axle.  Pinion seal?  Should I fix it before I test drive it to check the new brakes?

[Jerry Roberts]

Just work on one thing at a time . in the photo it doesn't look like too bad of a leak . And make sure that the vent on top of the differential isn't plugged as that will cause a leak . Your jack stands didn't cause the leak . 

[Loren]

When you get around to replacing the seal, check out some of the treads on this site.

The original seals are almost impossible to replace under the car. They are very fussy.

I recommend you go to NAPA for your replacement. They sell a modern seal that's a lot easier to install under the car.

Further, if the yoke is worn NAPA has the sleeve repair for it.

[DJK]

I had a heck of a time trying to install the pinion seal from Andy Bernbaum, ended up placing my heat gun under the diff aimed at the front, went out back for 10-15 mins. to play with the grandkids, came back in, seal went in fine. PS I fabricated a seal driver from 3" diameter thin wall pipe w/ a plate welded on the end.

[keithb7]

All these old cars are prone to leak somewhere.The diff leak is not a big deal. Just keep your eye on the diff level until you get to it.

 

Your shop looks like mine. No hoist....What worked well for me was degreasing and cleaning. I went to a farm animal feed & tack type supply store. I bought a good sized round, robust plastic feed bucket.  Probably designed to feed sheep or goats or something. Lower profile, put probably 2 ft diameter or so. It's great for fluid changes and cheap. Go to an auto store and a similar type oil collector container is 3X-4X the price. It also worked very well as a solvent tank when needed. I'd get a solvent brush and clean my parts in some solvent in the tub. I had a 5 gallon pail that I would dump the dirty solvent in. When full of old brake fluid, engine oil and solvent, I'd take in to the oil recycling facility to dispose of. The bucket also went under components like your diff seen here. I'd use a hand pump-type pressurizer spray bottle. Put solvent in it. Spray solvent on the diff and use a brush and de-grease everything. Catching it in my feed bucket. Next day when the remaining solvent on the diff evaporated, everything looked great, and clean! Then it's easier to trace an oil leak too.

 

It does appear that the pinion seal is at least partially responsible for your oil leak seen in the pic. Oil can start leaking there and work its way down to the bottom of the diff carrier housing and then drip to the ground from there. With an old car there generally is long list of issues to address. This one, to me, is not a priority to get the car running and begin road testing. In my experience, road testing is a big reward for some work done and really helps in keeping you motivated. You can go back and address the diff oil leak later.

 

If you are going over your car, consider pulling the rear axles out. Replace the outer axle bearings and seals. Pull the diff carrier out and install a new main gasket. Add a skim of silicone to the gasket on both sides. When the axles and brakes are buttoned up, reinstall the wheels and lower the car back to the ground. Or at least on blocks to allow yourself some room to work. Then you can get to the pinion seal. I figure its easier to deal with the pinion nut when the axles and wheels cannot turn.

 

Sure be nice to have one of these hoists, but....Its likely not in the cards for me. This was at the exhaust shop last week. You can see the results of my degreasing techniques in my simple, ill-equipped garage. The rear end was literally caked with 80 years of road grime and oil leaks. Scrape the big stuff off, then the solvent and brush that I mentioned above. Plenty of shop towels, and many many floor sweeps later, It's coming along.

 

You're going to love the concentric brake tool. It'll net you very good results when used properly.

 

 

Edited May 1, 2020 by keithb7

[greg g]

There is a diff vent to allow heat and pressure from the diff if it is plugged it will seek the route of least resistance.  Look on top where the brake line splits. The splitter fitting is also the vent. The top piece of the assembly should wobble easily.  If it doesn't it is clogged.  Some penetrating oil and compressed air after soaking should clear it. If not you may need to remove it to clear it, unfortunately that will likely require a brake bleeding session after the lines are reattached.

[desoto1939]

greg, question sinc e the diff vent  goes through the brake blocke connector why would you then need to rebleed the brakes if you took out the vent tube. The vent tube goes throught the hole in the three hole brake block unless I am missing some understanding on the vent tube.

 

Rich Hartung.

[Merle Coggins]

Good advice above. All I wanted to add is that you may have just noticed this leak after having the car on jack stands if only the rear was jacked up for some time. This would have changed the pinion angle enough for more oil to flow against the seal. Sitting flat on the ground there may not be much oil against the seal. So, you may want to check your fluid level for now, and top up if necessary. Then worry about changing the pinion seal once you have other things sorted out. It's minor for now. Just keep an eye on it and keep the diff full of oil. It'll be a project for next winter. 

[kencombs]

3 hours ago, desoto1939 said:

greg, question sinc e the diff vent  goes through the brake blocke connector why would you then need to rebleed the brakes if you took out the vent tube. The vent tube goes throught the hole in the three hole brake block unless I am missing some understanding on the vent tube.

 

Rich Hartung.

All of them I've seen have two seperate passages.  One for the bolt/air and a seperate path for the brake fluid.  they never intersect.

[DJK]

5 hours ago, greg g said:

There is a diff vent to allow heat and pressure from the diff if it is plugged it will seek the route of least resistance.  Look on top where the brake line splits. The splitter fitting is also the vent. The top piece of the assembly should wobble easily.  If it doesn't it is clogged.  Some penetrating oil and compressed air after soaking should clear it. If not you may need to remove it to clear it, unfortunately that will likely require a brake bleeding session after the lines are reattached.

I removed my diff vent to find it plugged completely. A little digging and poking, brake cleaning, all is good. Don't remember having to disturb the brake lines to do it.

[greg g]

Thought you might need to break the lines to remove the vent to clean it. Then might introduce air into the brake pipe which would then need purging.  Never messed with mine other than to check it movement.

[DJK]

1 hour ago, greg g said:

Thought you might need to break the lines to remove the vent to clean it. Then might introduce air into the brake pipe which would then need purging.  Never messed with mine other than to check it movement.

The top may move, but you need to remove to verify no rust inside.

[Dodgeb4ya]

You don't need to remove the brake lines.

Just use a wrench or socket and remove the junction block /vent bolt. Take it to the bench and clean it up.

Put it back when done.

Edited May 2, 2020 by Dodgeb4ya

[greg g]

Picture worth buncha words.

 

[Ulu]

Good engineering too. They saved one bolt plus 15 sec to install it. Per car.

Just on P15's that's maybe 20 cents a car or $100,000 over the whole series back then.