Rear Axle Leak Question

[Ralph Pearce]

I recently got the '48 running reliably (faulty ignition switch), and have begun taking it out on short excursions about town.  I had the differential fluid replaced, and now see that it's leaking from a spot on the top/back end of the differential, along a place where there's a weld or maybe just some kind of sealer.  Any and all assistance greatly appreciated.

 

 

[P15-D24]

Make sure it is not over filled.

Make sure the vent is open, It is located on the "T" brake line fitting. 

If you have a crack in the case it can be welded. 

[MBF]

I'm not sure exactly what is leaking w/o crawling under the truck, but could it be leaking around the bolt that mounts the bracket for the brake line?   Have you made sure that your vent isn't plugged and that the vent cap moves freely? 

[Jerry Roberts]

After you check to see if the vent is open and it is not overfilled , and if you don't want to have it welded . Drain it down a bit , clean the area , and apply a bit of black silicone sealer . 

[BigDaddyO]

You sure it's not your brake line leaking?

[Ralph Pearce]

You sure it's not your brake line leaking?

 

Hi, no it's not the brake line; not clear and doesn't mess up the paint.

[48Dodger]

I agree with checking the vent.

 

But to be different.....is there a leak, flowing down the bed/frame that is landing (dripping down) on the differential?

 

48D

[Don Coatney]

The vent is pictured below. It can be seen in the second picture securing the block where the brake lines connect.

 

 

[Dodgeb4ya]

I have seen a 1948 chrysler rear end leak at that same weld seam.

[Jerry Roberts]

I had one that leaked there , it was a 1939 rear end . Original rear end with a VERY poor weld from the factory . I don't know how it ever passed inspection . 

[Ralph Pearce]

So I've located the vent and the cap spins around on top, but how do you know if it's open?  I cleaned up the area where the leak is coming from and there is no visible crack, so I believe that it's coming out from under the edge of the weld seam.  I think I'll try Jerry's idea with the sealer for now, especially since it's high up, then monitor. 

[Don Coatney]

So I've located the vent and the cap spins around on top, but how do you know if it's open?

 

You can unscrew it (as it will not disturb anything by doing so) and blow compressed air through it. However from the other responses it most likely is a faulty weld.

[Desotodav]

The breather is more or less just a bolt with a hole through the center with a small metal cap that sits on top - there is no open or closed position. The top cap can be removed for cleaning underneath if you wish as it's just pinched at the bottom to stop it from coming off. The whole breather bolt can actually be removed if you wish as it is just a mounting bolt for the 'T' piece and is not connected to the pressurized brake lines which meet at the 'T' joiner fitting.

[Fernando Mendes]

I had years ago(2008) at the same local leak but never discovered.I welded but is very difficult to see.My vent was not clogged too.

[Fernando Mendes]

[Ralph Pearce]

Thanks you guys!

So I cleaned things up and applied 100% silicon black gasket sealer. After test driving, I found that there was still a small leak. When I applied another layer, I could hear some pressure bubbles and remembered the advice about the vent. Removing the vent cap, I found the vent clogged with sludge. I cleared it out and reapplied a nice even layer of silicon around the entire circumference. Keeping an eye on it, but no leaking after many miles

[BobB]

Has anyone tried one of the stop leak products that are available? Are they damaging? Do they work? Thx Bob

[ggdad1951]

Stop leak stuff is a short term fix IMO

[Jeff Balazs]

They are a "might work" option at best. They work by causing the sealing gasket to swell. If the gasket or seal is in good shape and is just weeping a bit they might work. At best they may buy you some time before you have to make the real repair. At least that has been my experience.

 

Jeff

[JBNeal]

the only stop leak I recommend is that goo ya put in the lawnmower tires...stop leak in radiators, engines, transmissions, axles, etc. works sometimes, but ultimately it only buys ya time until the actual repair needs to be completed

[Ralph Pearce]

So here's maybe a better answer.  I recently noticed that the leak was beginning to dribble through the gasket sealer.  I looked into welding, but the welder said that unless the axle was drained and thoroughly cleaned (inside and out), that oil would contaminate the weld making it porous.  Looking into JB Weld suggestions on the internet, it appears that many folks have had success repairing cracked blocks, etc.  Checking with a couple of mechanics, they gave an optimistic thumbs up.  So I cleaned the hell out of the area with lacquer thinner, wire brush, and sandpaper (for texture), and applied a nice coat of JB Weld starting well before and ending well beyond the suspect area.  I got the strongest version, which happens to be clear.  So far, so good.