Hot Rods 9" Ford Third Member - New Gasket Is Leaking Gear Oil

Finally got a good used posi 3:70 third member for the 9" in my 32. Bought a FelPro gasket for it, put yellow glue on the housing and also on the gasket, waited for it to tack up and slipped the gasket over the studs in the housing. Then took black silicone and ran a ring of sealant around each stud.
Fought with the third member for a while, but finally got it to slide on the studs and bottom out.
I bought new lock nuts and copper washers, installed them and gradually tightened them up in a criss cross pattern. When I was sure they were tight, I filled the housing with 2 1/2 quarts of gear oil. (This third member doesn't have a fill plug, so I had to use a 5' hose with a funnel and go thru the axle tube into the center of the housing). Went inside for a while to cool off, came back in the garage to find a large puddle of gear oil on the floor, the leak is from the bottom of the third member. Tried tightening up on the bolts, but it still leaked.

After sopping up most of the oil on the floor, I removed the third member to look at the gasket.
Taking a razor s****er to the gasket, I realized that it was stuck pretty well to the housing, and the silicone was stuck well, too. The housing is powder coated, and I still have to get the gasket completely s****ed off.

I don't know what happened here, the gasket I bought was for a 66 - 86 Bronco 9", and the new one I bought today is for a 68 -76 Ford Torino 9". I have no clue what the housing that was installed in the car came from. I don't know what the difference in the gaskets would be, but thought I'd try another part number in case the first one was the wrong part.

Ideas?

Thanks,

Jim

 

I’ve never used a gasket with any removable carrier differential. I just use sealer.

 

What sealer worked the best for you?

 

I use a paper gasket with a thin smear of silicone on each side, clean surfaces on both the housing and third member. copper or aluminium washers without sealant. For those without fill plugs install one axle then jack the other side right up and tip it in the tube.

 

Just a thin smear of ultra black, no washers or gaskets. The one time I used a paper gasket it leaked too.

 

Housing is powder coated? I'd look at it real close to make sure all the coating is off the gasket surface and studs.

Paper gasket and some non hardening sealer like Permatex Aviation should work fine.

 

I've been rethinking installation of the paper gasket, and I seem to remember that the holes for the bottom studs were a little bit off. I thought that the silicone sealer would make up the difference and seal it up OK. Looks like that was wrong. The housing and studs are powder coated, and that will need to be removed. I plan to use Gasga cinch on the new gasket that I had to order.

 

GM head gasket sealer is my go to for all questionable area's. Which is basically Permatex aviation sealer.

 

Since this sounds like a bit of a conglomeration of parts, you need to make sure the housing is vented and the vent is not obstructed. Heat will build up and will push the gear oil out somewhere. Clean the housing and the pumpkin mating surfaces to bare metal put a THIN smear of silicone on the gasket, use copper washers, like Ford did when they designed the axle, and you should be good.

 

Thanks to everyone that responded to my problem. I now have several options.

Jim

 

Before I put it back together I would fill the housing as full as I could get it with the third member out and make sure the leak wasn't a housing problem. I would also take a real close leak at the third member housing around the bottom. From the amount you leaked the cause should be easy to see.

Back in the day I did a lot of 9 inch rears at the Lincoln/Mercury dealership. I remember the Ford gasket being a bit different than just paper. I'm thinking it was a composite gasket. I never used any sealant and didn't have leaks.

 

For all those that used gaskets long ago, can we still get any good gaskets anymore?

 

I used the paper gasket, I hit one side with Permatex spray first, to keep it ****ed down to the housing. Not a drop of a leak since. I used new copper washers and nuts.

 

Those housings often have the back cover,and axle tubes welded to the center area.If a cracked weld is covered by powder coat it could be leaking. If the next gasket/ sealer doesnt fix it then consider leak checking with solvent. Take a small straight edge,and check the gasket surfaces for any low spots. Check the carrier surfaces too.Just because its machined cast doesnt mean it cant have a low spot.

 

I used a Felpro gasket last week when I swapped mine. Thin RTV on both sides and reused the copper washers after annealing them. No leaks so far.

 

FelPro gaskets still work, eh? I haven't had any issues with them. I put one in the Corvette a couple weeks ago, not a drop

 

I used a lube locker gasket on the 9" in my car. It has survived a couple third member changes so far. It was expensive to start with, but not cleaning RTV off was worth it to me.

 

If you're going to swap centers often, use sealer (not rtv) between gasket and housing, and smear some grease on the gasket where the center sits on it. It will last through several changes.

 

Sounds like you need to hammer all the studs inside and remove the powder coat on the gasket surface and check it for flat. I’ve never seen or heard of anyone coating it. I use Permatex #2 on the pumpkin side of a gasket so it’s easier to get off. None leak

 

Ford 9" Rears are like Old Harley Davidsons; they like to mark their territory !
Silicone is the only way I've got a Ford 9" to stop leaking.

Happy Sealing,
VR&C.

 

I may never get it off again, but I used the Right Stuff, no gasket on the aluminum cover I put on my 8.8. Still dry as a bone after about a year.

Gary

 

I used gaskets and "the right stuff" rtv on these two and no leaks



The Henry J I got a little over zealous with the blue rtv 10 yrs ago, but again no leaks ....... but I swear there's a leak on the backside of the housing where I circled

 

That, sadly, is not unusual.

 

For housing seepage after ***embly, I use epoxy putty. I prefer the blue/yellow stuff but JB Weld makes one, too. Wipe the area with thinner then smear some in the leak. You can sand it down after it dries. Touch up the paint and done.

It works for seeping oil pans and gas tanks, too.

 

The new gasket came today, and it's the correct one, all the holes line up.
I stripped the powder coating off the housing, and am now looking at bare metal
on the third member as well.
I ***ume that I need to put a light coat on the housing and spread it with my gloved finger; how long do I wait before sliding the gasket over the studs and press it down flat on the housing? Then, I put a similar coat on the gasket, with an RTV ring around the studs and how long do I wait before installing the third member? Do I need to put RTV on the third member sealing surface as well? Also, how do I make sure the third member is completely seated, all the way down?
After snugging up the locknuts with fresh copper washers, how long do I wait before cranking them down?
After that, how long do I wait before filling it with oil?

I'm asking all these questions because I don't want a repeat of what happened last time.

Thanks, Jim

 

RTV? ugh.

There should be no need to use any sealer on the studs if you use copper washers.

I have no leaking issues using permatex aviation sealer on the bottom half of the gasket, both sides, and new copper washers. But I'm RTV phobic, so maybe don't listen to me? Ford did not use RTV on them from the factory, and they did not leak.

 

Just get a "Lube Locker" gasket ...done!

 

Here ya go.

 

Sorry, I tried to include this as well but it didn't want to go.