Real Axle Oil Leak

[Dan D.]

My 57 leaks rear end oil, left side, slow leak drips down the axle housing/backing plate interface area. Inside of backing plate - brake shoe area is dry. Right side is fine.

I have replaced the bearing o-ring - still leaks.

Could this be the bearing? Probably original, but spins fine, no noise anywhere.

I think it is leaking around what looks like a vent hole in the bottom of the backing plate - the gasket is notched for it and the axle retainer plate is too. But why is a vent hole required here?

If the bearing, looks like a tough job to replace. My son-in-law has a good hydraulic press, but would need to fab a special tool of some kind to pick up the bearing inter race.

If I have to replace the bearing, are the ones from our suppliers okay, or are they off-shore junk.

I have it apart right now, but would like to get it fixed and back together fairly soon.

Appreciate any help.

Dan D.

[Dan B.]

Re: Real Axle Oil Leak

Dan,

The rear wheel bearing retainer plate is supposed to have a gasket there. Did you degrease and clean the surface well and install a new gasket with sealer last time? The retainer by design has an oil return slot as the original style bearings were "open". The bearing itself should be still fine if it turns smoothly.

Fel-Pro 5188 is the part number for the gasket, readily available at the local parts store.

[Dan D.]

Re: Real Axle Oil Leak

Thanks Dan for responding.

Yes, I cleaned the retainer plate and backing plate, Permatex the gasket - both sides.

While the inside surface of the bearing is open, the outside is sealed. But looking at the bearing, the outside does not look good. That side should be sealed, and it looks like it is. Kind of difficult to see, but the seal does not look good, and there is rust around it. That seal may have failed, letting oil through the bearing and dripping down to the return slot.

I have not figured out how that slot can direct oil back in. The hole in the backing plate is below the flange on the axle housing, so it seems to me that any oil coming through that flange slot would just go through the hole in the backing plate and out. Oil could not be directed back into the axle housing because it is below the axle housing flange.

So it seems to me that the slot and hole are some kind of pressure relief, perhaps from brake heat.

The only place that oil is present is on the back side of the backing plate, and below the axle housing. The rest of the backing plate is dry, including the inside - brake shoe side. All dry there, and the brakes work good.

So it seems to me that the oil is dripping into the flange slot and out the hole. That can only be from through the bearing, or past the single o-ring. The o-rings are known to be a problem.

Question - 58 and up have a better bearing and two o-rings, plus both sides of the bearing are sealed. Will that bearing work in a 57? The bearing is wider, but the spacer may be thinner to compensate for it. I don't relish having to remove that bearing, but I may have to. It doesn't look like there is much inside race area to press against.

Does this make sense?

Dan D.

[Paul Y.]

Re: Real Axle Oil Leak

The new bearing is a one piece/ seal included and the axle will come out after taking the four bolts out and using a slide hammer on the axle attached to the lug bolts. (My friends and I used to use a log chain attached to the lug bolts and it would come out by snapping it a few times.) A new gasket is needed under the axle bracket that holds the axle in with the four bolts. I never use sealer on that gasket as the 90 weight grease only comes out that area if the axle bearing is compromised. Replace both sides as it will save you from having to do it at another inopportune time. Try to find a bearing with two O ring grooves and lube with a touch of grease. The bearing retainer can be removed with a puller, or pickle fork, and tapped back in with an item large enough to slip over the axle. It might be a good time to change the 90 weight in the differential also. Don't forget the positraction additive from Chevy if it is a posi. Keep an eye on the front seal of the third member also as the seals are all probably the same age. If you have all the new parts and fluid it will not take long to be back on the road. Paul

Thanks Dan for responding.

Yes, I cleaned the retainer plate and backing plate, Permatex the gasket - both sides.

While the inside surface of the bearing is open, the outside is sealed. But looking at the bearing, the outside does not look good. That side should be sealed, and it looks like it is. Kind of difficult to see, but the seal does not look good, and there is rust around it. That seal may have failed, letting oil through the bearing and dripping down to the return slot.

I have not figured out how that slot can direct oil back in. The hole in the backing plate is below the flange on the axle housing, so it seems to me that any oil coming through that flange slot would just go through the hole in the backing plate and out. Oil could not be directed back into the axle housing because it is below the axle housing flange.

So it seems to me that the slot and hole are some kind of pressure relief, perhaps from brake heat.

The only place that oil is present is on the back side of the backing plate, and below the axle housing. The rest of the backing plate is dry, including the inside - brake shoe side. All dry there, and the brakes work good.

So it seems to me that the oil is dripping into the flange slot and out the hole. That can only be from through the bearing, or past the single o-ring. The o-rings are known to be a problem.

Question - 58 and up have a better bearing and two o-rings, plus both sides of the bearing are sealed. Will that bearing work in a 57? The bearing is wider, but the spacer may be thinner to compensate for it. I don't relish having to remove that bearing, but I may have to. It doesn't look like there is much inside race area to press against.

Does this make sense?

Dan D.

[Tom P.]

Re: Real Axle Oil Leak

I just cannot believe that NCRS folks are not up to speed on this issue!!!!
VERY FIRST, there are only two places that a 56-62 Corvette rear axle bearing can leak: around the O-ring on the outside of the bearing; THROUGH the bearing where the seal is (more common source).
NEXT, the hole in the backing plate IS NOT, repeat, IS NOT a vent. It is a drain hole so that in the event a leak should occur, THE THEORY was for the oil to run down to that hole and onto the OUTSIDE of the backing plate, thus, NOT getting oil onto the braking surfaces. Sometimes it worked, sometimes it did not. You are lucky that yours drained to the outside as designed.
The 55-64 passenger car4s have the exact same design rearend-brakes-bearings.
I'm only vaguely familiar with these rearends, I've been working on, and rebuilding them, for over 55yrs.
The service manual VERY CLEARLY provides instructions for replacing the bearing. I'll provide brief pictures.
For early Corvettes, there were THREE (actually 4) different rear axle bearings: 56(same for 55-6 car); 57(ONE year only); 58-62(same for 58-64 cars). ALLLLLLLLLLLL 55-64 axle bearings were ball bearings--------------EXCEPT for Corvettes equipped with Positraction, they got a roller bearing, which is dimensionally and 100% interchangeable with the 58-64 ball bearing (the roller bearings are LONG discontinued!).
As I mentioned, there are 3 sizes of axle bearings for 56-62 Corvettes, shown below: 55-6(RW507 series), 57(RW307 series), 58-62(RW607 series). SOME, not all replacement bearings have 1, some have 2 O-rings. Some have big grooves for thick O-rings, some have small grooves for thin O-rings. Depends on the bearing manufacturer. Back then, there were many bearing manufacturers.
SOME bearings have a seal on one side and a shield on the other side (inside). Some bearings were open toward the inside of the housing and were lubed by rearend oil.
I've attached an article I put together several years for another publication. It is 100% out of the Chevy service manual, but with color pictures and a few more details, for replacing 55-64 (56-62 Corvettes) rear axle bearings.
Hope it helps.

[Dan B.]

Re: Real Axle Oil Leak

Tom,
Thanks for clarifying the function of the slot in the bearing retainer. Makes perfect sense since it's outside of the tube.

[Terry D.]

Re: Real Axle Oil Leak

I'm assuming you have looked at the axle housing and it is not nicked up. Sometimes Bubba tries ti use a screwdriver ti get the bearing out and gouges the axle housing, new bearings will not fix that. Loctite make a solution for that, not the ideal fix, but will do in a pinch. Not being home at the moment I can't tell you the number, but if you need it I can get it tomorrow. We did this on a friends car and 3 years later it is still holding up.

[Dan D.]

Re: Real Axle Oil Leak

Thanks Terry,

The axle housing looks pretty good, but not perfect. It looks like the bearing may have spun at one time or the other, but the fingernail does not pick up any ridges. It appears only to be coloring.

Also I have owned the car since 1971 and it did not leak, but it sat for several decades when life got in the way. It only started leaking after being driven again recently. That tells me a seal dried out.

Looking more closely at it, the back of the bearing (seal side) is dry, so no oil made its way past the bearing seal. The axle came out without any effort, and the bearing and surrounding area was wet, so that tells me the o-ring is the problem, even the new one. That o-ring is really wimpy, only 0.101 thick, I think.

Loctite 609 retaining compound would probably fix it. I think another member on the forum has done that, and it works. The only thing I worry about with that fix is if I have to take it apart again it would probably be difficult to get the axle out.

Right now I am hung up whether to try the Loctite, or replace the bearing.

Will advise.

Dan D.

[Tom P.]

Re: Real Axle Oil Leak

These bearings SHOULD BE a mild interference fit. It should require 3-4 hefty whacks with an axle puller to remove the bearing. Then to install the axle, it should take 2-3 whacks with a 2-3lb hammer. That is how tight they SHOULD fit.
Our 56 has a 60 axle housing, and it only takes 1-2 whacks with an axle puller to remove the bearing. I really wish it was a little tighter.

[Dan D.]

Re: Real Axle Oil Leak

Okay Tom, I think that explains it. (you are my savior). I can pull it out, or push it in with my fingers, so it may very well have been spinning.

It looks like retaining compound is the only answer, other than another rear, which I do not want to do.

My car was raced in its previous life, and I believe the 3rd has been out, perhaps several times. Originally Powerglide, I think it had 411s at one time.

Right now i don't believe it would do any good to just replace the bearing.

Dan D.

[Dan D.]

Re: Real Axle Oil Leak

I cleaned everything up today. I am going to buy a 58-62 double o-ring bearing too. I'm all but sure the bearing was spinning in the housing.

But I am going to have to install the bearing dry, in order for the retaining compound to set up. Does this sound right?

I also have some square o-rings - same size. Does anyone think they would work better than the wimpy round ones?

Dan D.

[Tom P.]

Re: Real Axle Oil Leak

I cleaned everything up today. I am going to buy a 58-62 double o-ring bearing too. I'm all but sure the bearing was spinning in the housing.

But I am going to have to install the bearing dry, in order for the retaining compound to set up. Does this sound right?

I also have some square o-rings - same size. Does anyone think they would work better than the wimpy round ones?

Dan D.

NO!
The 57 bearing is ONE YEAR ONLY!
As seen in the pictures above that I posted, the 57 bearing(RW307 series) is only about .90in wide, whereas the 58-62 bearing(RW607 series) is 1.00in wide. Thus, if a RW607 bearing is installed into the end of a 57 housing, it will protrude about 1/8in out from the end of the axle tube. THEN, when the 4 bolts are tightened on the bearing retainer, the 4 corners of the retainer will be bent and the 4 sides of the retainer will not be tight against the gasket.
As an alternative, a 58-62 axle bearing retainer COULD be used, but if a 58-62 bearing(RW607 series) is used-----------------the question is, will it fit any tighter in the end of the axle tube??? (also 58-64 pass car retainer)
Below is a comparison of a 57 and a 58-62 bearing retainer. As can be seen, the 58-62 retainer is slightly thicker than the 57 retainer.

[Dan D.]

Re: Real Axle Oil Leak

Hi Tom,

Apparently there is a difference between yours and what CC says.

Corvette Central shows the 58-62 bearing, a W670 series, like you say. But they say it is .970 wide, - .070 difference. The picture looks like the 58 lock ring is less wide, which would compensate for it.

Also, they list the same retainer for 57-62. So is it possible that they have changed the configuration somewhat? They don't say if the 58 bearing will fit 57. So I don't know.

The OD for both is 3.00, so I don't think it will fit any tighter in the housing.

Maybe I should buy one of each, I could always send one back.

It would be easier to put the retaining compound on the one only O-ring bearing , and I am going to have to do that. The bearing will have to go in dry.

Your Thoughts?

Dan D.

[Tom P.]

Re: Real Axle Oil Leak

I only know these bearings by their common part number (NOT GM part number).
The 55-6 bearing is RW507 series.
The 57 bearing is RW307.
The 58-62 bearing (64 for pass cars) is RW607.
Some of the aftermarket sources, such as CC, Paragon, etc may have their own part number, but they still correspond to the industry bearing part numbers.

The GM part number for the 55-6 rear axle bearing (w/lock ring) is 900700 (translates to the RW507 series).
The GM part number for the 57 bearing is 907071 (translates to the RW307 series).
The GM part number for the 58-62 bearing is 907294 (translates to the RW607 series).
This is the best information I can give you.
The LONG, LONG discontinued roller bearing for 58-62 FACTORY installed positraction. GM part number, is 7451415, Hyatt part number is JRN1542. Good luck ever finding one of those for less than $1,000!!!

[Dan D.]

Re: Real Axle Oil Leak

The RW numbers I referenced (same as what you say) were off of the pictures on their website. I know nothing of the GM P/Ns.

I think I am going to buy one of each bearing tomorrow. I'll let you know how I make out. I'm going buy a new flange too. Mine is beat up some. The studs fell out, the holes are raised some. I can press them back in okay - with Loctite, but I think I will just buy a new one.

My real challenge will be to be fit the bearing into the housing so it will not turn, and seal too. Retaining compound may be my only hope.

I feel good that I found the cause of the leak. Not too happy about the remedy is all.

Dan D.