rear wheel bearing life???

[Joe R.]

Re: rear wheel bearing life???

Realize this when thinking about lubricating the rear inner bearings. The key phrase here is inner bearings. Trailing arms have an inner and an outer bearing. That tool mentioned will lube the inner bearing ok. BUT to be able to lube the outer bearing you would have to fill the inner cavity of the bearing support with grease and then the grease would have to flow into the outer bearing WITHOUT getting past the outer seal. Now we can see if that happens the entire trailing arms will have to be taken down to clean and replace the emergency brake shoes.

It's virtually impossible to know how much grease would be needed to do the job correctly every time.

And yes the inner bearing is usually the one that gives trouble but the outer can and will go bad down the road sometime.

The above reason is why GM later stated that the bearing were lubed for life and needed no maintainence. Yes, lubed for the life of the bearing!!!!

You send your trailing arms to "Bair's" and I'll guarantee them because they are the best at what they do and they do it right every time.

JR

[Roger O.]

Re: rear wheel bearing life???

Not quite sure what you're referring to Roger. Do you mean axial load? I believe that's split fairly equally between the inner and outer bearings and of course why roller bearings were chosen over ball.

To be honest I'm not sure what to call it. Looking at the bearing it is wider than the outer,its also at a different angle and smaller in diameter.
The bearing would seem to have to keep under control one end of the 1/2 shaft that has a wobbly u-joints at both ends and is moving up and down and changing angles all the time.
It just seems like if the inner and the outer did about the same thing they would have made them the same.
And the fact that GM made a special tool to lube just the inner's in my mind would mean the inner's were under more stress.
I also get the feeling that the inner bearing isn't under a constant preload like the outer.( you can't rattle the outer bearing with the car on the ground but you can rattle the inner).
I just think there is more to the inner bearing from an engineering standpoint than just a bearing holding up a wheel.

[Roger O.]

Re: rear wheel bearing life???

Further to Roger O's post with the bearing greasing procedure using J-24488, Vette Vues Aug '96 reproduces an article from Chev Service News, Nov'92 issue, giving more info.

"A new higher load capacity lubricant Shell EP-BP, P/N 9985038, was released in Feb '72 for use in production. Engineering is recommending the following lubrication procedure for servicing all Corvette inner wheel bearings....new vehicles at 12000 miles and a 24000 mile intervals after...

[followed by Roger O's pic of GM geasing procedure text] .... [mentions new lubricator J-24488]".

Interesting , I'll have to look that up , thanks for posting.
I really felt like I was doing a service to my customers by going by the GM recommendations and injecting the rear bearings. I've never had to do any of the bearings I injected for bearing failures. Personally I'm a believering in the tool for maintenance and I charged a very small fee to do it , $68.84 .

[John H.]

Re: rear wheel bearing life???

I also get the feeling that the inner bearing isn't under a constant preload like the outer

Roger -

Properly set up, there should be no axial preload on either the inner or outer spindle bearing; axial preload will destroy a tapered roller bearing in short order.

[Roger O.]

Re: rear wheel bearing life???

axial preload will destroy a tapered roller bearing in short order.

Does that apply only to greased bearings unlike pinion bearings in the differential ?

[Steven B.]

Re: rear wheel bearing life???

I have never used the KM tool but a friend borrowed mine to do his '66 350 HP, 4 spd. The car had a little over 50,000 on it when he used it just before a trip from Indiana to Denver. A couple of hundred miles outside of Denver the left side let go. When Bill got it to a Chevy dealership and was torn down inners and outers were gone, but one had grease and the other was dry.

[Michael W.]

Re: rear wheel bearing life???

I have never used the KM tool but a friend borrowed mine to do his '66 350 HP, 4 spd. The car had a little over 50,000 on it when he used it just before a trip from Indiana to Denver. A couple of hundred miles outside of Denver the left side let go. When Bill got it to a Chevy dealership and was torn down inners and outers were gone, but one had grease and the other was dry.

This supports the idea of a scheduled disass'y every 40K miles or so for proper mtce. I have no faith in the tool being described or some other injection of grease and 'hoping for the best'.

[Terry M.]

Re: rear wheel bearing life???

This supports the idea of a scheduled disass'y every 40K miles or so for proper mtce. I have no faith in the tool being described or some other injection of grease and 'hoping for the best'.

I suspect use of this tool is "better than nothing," but although I own one, I never used it. When I got play in the driver's side rear bearing (61K on the car now) I had someone with all the tools replace the bearings. The report was: "They sure didn't put much grease in them originally." I can believe that.

[John H.]

Re: rear wheel bearing life???

Does that apply only to greased bearings unlike pinion bearings in the differential ?

Roger -

I don't know - pinion bearings do call for a light preload, but Chevrolet has always gone to great lengths in the wheel and spindle bearing adjustment/setup procedures to ensure that there is no axial preload at all on the tapered roller bearings used in those applications.

[Michael W.]

Re: rear wheel bearing life???

One of the design difficulties with any rolling element bearing and particularly with double tapered rollers like a typical wheel bearing is accounting for expansion and contraction of the assembly under all operating conditions. While the damage from being 'too tight' is easy to imagine when the minute surface contact area from the roller to the race is considered, equal or worse damage can be incurred from being 'too loose'. The roller can lose contact with the surface of the race long enough to stop rotating and then be forced to accelerate back to operating speed when contact is made again. Repeated occurrences of this will degrade the bearing surfaces similar to extreme wear on an aircraft tire after landing.

The conventional method of dealing with the two extremes is by allowing a measured amount of 'cold' clearance such as is done with front and rear wheels on C2/C3 cars. Differential pinions are set up by measuring and setting rotational resistance to a precise and essentially tiny amount of preload measured in inch pounds of torque (not foot pounds).

Two ways of achieving the same thing.

I spent years working with high speed rollers bearings where the outer race assumes a tri-lobed shape at operating temps. This ensures that the rollers (which are travelling supersonically themselves) touch the surface at least three times per revolutions to minimize skidding as outlined above. No synthetic oil required either, but that's a different discussion.

[Bill M.]

Re: rear wheel bearing life???

Roger -

I don't know - pinion bearings do call for a light preload, but Chevrolet has always gone to great lengths in the wheel and spindle bearing adjustment/setup procedures to ensure that there is no axial preload at all on the tapered roller bearings used in those applications.

Back in the 70s, Ford had a very light preload on front wheel bearings (like 10 in-lb). I mis-read the book and applied 10 lb-ft. Those bearings did not last long.

[Gary R.]

Re: rear wheel bearing life???

Terry,
The bearing greaser is snake oil unfortunately. I have pulled a lot of spindles apart, some virgin originals,others rebuilt. The amount of grease varies in each, the originals had enough grease in the day but that day was 40 years ago and the grease dried out and is hard packed.

I played with the tool a few years ago to see just how far I could pump grease in and it was never past the inner bearings and usually a mess.

I can also say the same thing about adding grease in an old steering box through the cover, most times it's useless other then to maybe satisfy an owner into thinking he saved his box. I have pictures here somewhere of both jobs showing just how far the grease went in and didn't mix well if the old stuff was dried out.