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Spun wheel bearing traced to gasket thickness

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steveg

steveg

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[Xposted on the Autox list]

If you’ve had a spun rear wheel bearing and/or leaking seal, this may be of interest.

Recently one of my rear wheel bearing seals started to leak. Ordering a new seal from Tom’s Import Toys, Tom Monaco mentioned the leakage was caused by heat from the bearing spinning in the housing, and that he’d replaced about a hundred rear wheel bearings to fix this problem. The cure was to install a new bearing using a combination of heat and cold to shrink-fit the bearing into the hub and onto the axle. I’m guessing the hub housing has some wear if the bearing’s been spinning.

According to the Manual, Section J, the bearing spacer must protrude .001” - .004” beyond the paper gasket. This allows the lug nuts to tightly metal-to-metal grip the outer ring of the bearing in the hub. The inner ring is tightly gripped by the center octagon nut. (Thanks to Gary Hodson for pointing this passage out.)

In my opinion, the spun bearing problem is caused by excess thickness of the replacement gaskets, which prevents positive gripping of the bearing outer ring, as called for by the manual.

I measured my non-gasket clearance at .004”. This can vary as the thickness of the bearings can vary by a few thousandths (.900” and .905” on two old bearings I have).
The Moss replacement gasket is .015” thick and compresses down to approximately .011” – therefore the bearing outer ring is not gripped at all and the hub depends on the shrink fit of the bearing only.

In my opinion, the solution is to make your own gasket from paper such that the thickness is .001” less than the protrusion as measured above. Legal pad paper is .003”; copier paper is .004”; 9x12 envelope paper is .005”.

If your car doesn’t have the o-ring, or you don’t have a micrometer, you could leave the gasket off and use a thin bead of gasket goop, such as Right Stuff or Form-a-Gasket to effect the oil seal.

Axle flange note: The outer edge of the axle flange is not distorted by being unsupported by the gasket. Because of the thickness of the brake drum and splined hub flange, in combination with the strength of the hub itself, the flange will not distort by tightening the lug nuts.

Would be curious to measure an original gasket from back in the day.

Documentation:
https://www.pbase.com/stevegerow/healey_rear_bearing
 
Steve, I remember the gasket being extremely thin when I replaced a leaking axle seal back in the 70's. Very much like the transmission gaskets, you could just about see through it when it was wet. I just measured some OE trans gaskets that I have and they all came in around .009". I've got some rear brake work to do in the next few months so I may just pull an axle and measure the gasket.
 
I don't use gaskets !

I tested a product designed by Permatex on my own car before using it on a regular basis. It's Permatex Gear Oil RTV gasket maker, 81182.

I fitted my new 3.54:1 differential and the axle bearing/flange surfaces without any paper gaskets and have now reached 1500 miles with not a drip of oil.

Make sure the surfaces are clean, apply a thin bead, then tighten everything up not much more than finger tight, go back two days later, "it takes a while to semi harden" and then tighten everything.

As they say in the UK, Bobs your uncle.

Johnb
 
I Had a similar problem but the hub was worn and I could not get a tight fit of the bearing. A quick call to Norman Knock and Healey Surgeons told me to Knurl the hub which I did and reassembled it to the diff housing been good to go ever since.
 
As a followup, I disassembled my other rear hub, found the bearing to have spun, installed new bearing with Loctite Bearing Mount Stick, measured clearance at .004" (same as other wheel). Installed a .003" paper gasket with a little Hylomar. Hopefully Bob's my uncle. If the combination of clamping and Loctite gives out, next time will knurl.
 
4 years later, my left rear wheel started leaking out the flange. The spring-type lug nuts were all almost loose so maybe that contributed to the problem. Will be replacing those with loctited Dorman nuts.

The bearing and seal are OK.

The .003" copier paper gasket is completely gone except for a couple of small pieces. Bad idea. No evidence of Hylomar either.

screenshot.1901.jpg


Will be redoing with this with no gasket:
screenshot.1902.jpg
 
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Thanks for bringing this thread up again. I just test fit my new (to me) axle housing, hubs, differential and half-shafts. All looks good, so I will be looking for that Loctite Bearing Mount Stick and Permatex Gear Oil RTV gasket maker, 81182.
 
John Turney said:
Thanks for bringing this thread up again. I just test fit my new (to me) axle housing, hubs, differential and half-shafts. All looks good, so I will be looking for that Loctite Bearing Mount Stick and Permatex Gear Oil RTV gasket maker, 81182.
Click to expand...

IMO if you skip the too-thick Moss gasket, you can depend on the clamping force of the lug nuts to hold the bearing in place.
 
There are several threads on the gasket thickness issue on the Spridget board. Similar bearing/hub design.
Consensus is the same, current aftermarket paper gaskets are too thick to seal the axle to the hub properly.
Most people are either using house made thin gaskets or just gasket sealer.
BTW, many Spridget types are using a sealed bearing to reduce the amount of oil that is seen by the Axle to flange seal.
 
Used Permatex Gear Oil RTV gasket maker, 81182 to seal both axles and differential. This and home-made thin paper gaskets - suspenders and belt are acceptable here. No leaking. Also used the RTV for sealing drain and fill plug threads on Diff and Trans. I don't like the smell of gear oil.

Curious, does knurling require special machining or is it by punch and hammer technique?

Hey Steve, have you found a different lug nut for the adapters? i recall you mentioning dorman lugs. GONZO
 
Gonzo,
I ditched the copier paper gasket and used only the Gear Oil RTV in combo with Dorman 7/16-20 lug nuts with Permatex Orange Thread Locker.
I checked my other side and the standard spring nuts were tight with no leaking, so left them as is for now.
For the Dorman nuts, see the recent "Rear hub nuts" thread.

screenshot.1905.jpg
 
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John Turney said:
Thanks for bringing this thread up again. I just test fit my new (to me) axle housing, hubs, differential and half-shafts. All looks good, so I will be looking for that Loctite Bearing Mount Stick and Permatex Gear Oil RTV gasket maker, 81182.
Click to expand...
A follow-on to my earlier post.

I checked how much the bearing spacer protruded beyond the hub face on my left hub and found it didn't. I made an additional spacer out of 0.003" shim stock that I installed between the outer race and bottom of the hub, giving me the protrusion required. I then used the Gear Oil RTV. So far, so good.
 
John Turney said:
A follow-on to my earlier post.

I checked how much the bearing spacer protruded beyond the hub face on my left hub and found it didn't. I made an additional spacer out of 0.003" shim stock that I installed between the outer race and bottom of the hub, giving me the protrusion required. I then used the Gear Oil RTV. So far, so good.
Click to expand...

John,
Did you happen to measure the thickness of the bearing rim? That would appear to be the culprit.
 
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