Axle leak 8 3/4?

[am3rican]

I need help diagnosing this problem I just noticed. I took my 68 roadrunner out after about a month of sitting in the garage. When I got back, I noticed some oil stains in the driveway where she was parked. The stains were right under the rear axle. It's 3 stains, with the middle one being the largest (right under the diff). I crawled under the diff and the housing has a fluid on it. It looks like used cooking oil. It would make sense that it is gear oil. Any ideas where I can check to see it is leaking? What''s the most likely culprit and how difficult to fix?

The previous owner had installed a new 8 3/4 rear with a new drive shaft. It has 3.90 gears. I'd guesstimate that the rear was replaced about 10-12 years ago. Maybe 5000 miles since it was built.

 

[monaco66coupe]

The guy probably did a crappy job of sealing the gasket behind the pumpkin. First unscrew the plug to see if it is low on oil.
There is only one way to seal a leaky third member, removal.

 

[am3rican]

The guy probably did a crappy job of sealing the gasket behind the pumpkin. First unscrew the plug to see if it is low on oil.
There is only one way to seal a leaky third member, removal.

I get that, but when I've seen the pumpkin leaking, there's one oil patch under there. From the pic, it looks like there are three, including two on either side of the pumpkin.

 

[bm02tj]

Clean it up and then check it tomorrow if no leak take it for a drive and park and check each time before you drive till you find where the leak is

 

[monaco66coupe]

sitting a long time can affect that. Keep driving it, and watch it, is my suggestion. Now, if the vent is plugged, oil fumes can come out all over. it is on the left, top side near driver side.

 

[sleepar]

I would pull the axles and those seals and the pinion seal then that seal.... it's a warning of what's to come.... you shouldn't need hard parts.... but you can't escape the age of the gaskets and seals....

Sometimes these cars are like the painting golden gate bridge...

The pinion seal is the hardest nut to crack and Mark it so it goes back on the exact same and pinion yolk position the axles involve pulling the drums and some retaining bolts and the backing plate for the brakes... the axles come out and their are inner ad outer seals the bearings are packed in grease.... and put tape on the studs and the spline ends and handle them like glass.... when I put my axle back in I have a straight line painted on the length to see if it gets bent or twisted in the future....

 

[benno440]

OP, check fluid, check vent is clear, check if still leaking after a clean up and drive, if so , disconnect drive shaft, remove wheels, slide axles out a couple of inches, pull center out and replace gasket, reinstall

 

[am3rican]

What brand seals would you recommend? I plan on getting whatever is available on RockAuto.

 

[am3rican]

Update: I crawled under the rear axle and cleaned it up good with some degreaser. The axle tubes dont appear to be leaking. It definitely appears to be from the center housing. No play at all in the yoke.

I did not check the fluid yet but it def appears to be a slow leak. There was definitely some dried grease on there.

There are no new drops under the cardboard I placed under the axle.

I'll top it off and drive her around and check for any fresh leaks. If it does need a rebuild, i'll just take her to a reputable local place. I am contemplating going from 3.90 to maybe 3.23 gears. The 3.90 gears are just no good for cruising.

QUESTION: How do I check that the axle is venting properly?

 

[bm02tj]

Remove the vent and clean then blow through it

 

[nm9stheham]

The vent is part of the bolt that holds the brake line splitter on top of one of the axle tubes (ususally driver's side. Uncrew this out of the housing and clean it up; it will be a a hollow bolt and will have a little flappy cap on top. Don't overtighten it when you re-install; hollow bolts break easier than normal ones.

As for the leaking, after you have cleaned it up, see if the leak is from where the front section meets the housing (gasket) or at the forward end of the 'snout', right behind the driveshaft yoke (pinion shaft seal).

If the leak is slow, don't panic; these can go for years and 10's of thousands of miles with no real issues. The one thing to worry about is if it is from the pinion seal and if a pinion bearing is getting loose; if you grab the yoke and try to move it, it should not move around, only rotate a bit back and forth. If there is any sideways or forward/rearward movement of the yoke (pinion shaft), that is the time to take action before it deteriotes further and permanent damage is done.

 

[am3rican]

The vent is part of the bolt that holds the brake line splitter on top of one of the axle tubes (ususally driver's side. Uncrew this out of the housing and clean it up; it will be a a hollow bolt and will have a little flappy cap on top. Don't overtighten it when you re-install; hollow bolts break easier than normal ones.

As for the leaking, after you have cleaned it up, see if the leak is from where the front section meets the housing (gasket) or at the forward end of the 'snout', right behind the driveshaft yoke (pinion shaft seal).

If the leak is slow, don't panic; these can go for years and 10's of thousands of miles with no real issues. The one thing to worry about is if it is from the pinion seal and if a pinion bearing is getting loose; if you grab the yoke and try to move it, it should not move around, only rotate a bit back and forth. If there is any sideways or forward/rearward movement of the yoke (pinion shaft), that is the time to take action before it deteriotes further and permanent damage is done.

This is the most helpful response I have had in a long time. Thanks man

 

[am3rican]

Not sure what previous owner was thinking but seemed to have located the issue, at least a contributor. I checked the fill plug and it was way over full, like to the point where it was pouring out the moment I removed the plug. Took me by surprise. Luckily I put some newspaper and cardboard down. I forgot how foul gear oil smells. It must have been at least a 1/4 to a 1/2 quart overfull. Not sure how they could have overfilled it so much.

 

[am3rican]

Shaft seal is leaking. Ordered new one.

 

[HT413]

Shaft seal is leaking. Ordered new one.

Hey man, before you replace that seal, check which case you have. If it's the 742 or 741, you can replace the seal but if it's a 489, it's a bit more tricky due to the crush sleeve.

 

[am3rican]

It's a 742