RBrid

On this glorious day I am joyfully setting up a rear spindle run-out.

I have one shim that gives me a run-out of 0.001". Right at the lower end of the permitted GM range of [0.001", 0.008"].
Would you go ahead with this?
Or would you rather grind off around 0.006" from the slightly thicker shim? That would give me a final run-out of around 0.002".



Thanks! -Régis

DUB

I have without any problems....but I usually shoot for .001" to .003" MAX.

DUB

Sayfoo

Wouldn't "0" be the best, but a little is allowed?
.001 is much better then most of us have.

Mike Ward

Run out or end play? Two very different things. The surface you have the indicator mounted on has no factory spec for runout.

doorgunner

Mike Ward has a good point.

The way the indicator is set up---it would show end play......the amount of play the spindle has when the housing is pushed down as far as it will go/the indicator is set to zero on the dial/then the housing is lifted as high as it will go and the dial is read.

(Actually.....the spindle should be moved up and down to check for end play....but the vice is gripping the lower end of the spindle preventing spindle movement)

Runout on a spindle would be "sideplay"/runout on a brake rotor would be termed by most people as "wobble".

As for .001" endplay........a comparison would be a hair on your head, which would be around .005" thick....which shows how "tight" .001" actually is-----TIGHT-----not much room for grease once the bearings reach operating temperature.

'75

.001" end play will be fine. After you pack the bearings and do the final install, you probably won't be able to feel any play, but it will still be there.

RBrid

Sorry for the confusion guys. I meant to say end play and not run-out

And thanks all for your input. It sounds like I can go ahead with this particular shim that gives me .001" end play (that's the delta I'm getting when pushing the spindle up and down).

dugsgms74

I'm glad someone mentioned this. I'm getting ready to do my rear spindle bearings(bearings, tools and hardware on order) and the specs had me wondering. To me it seems like the rear wheel bearing set-up has alot in common with setting up a differential pinion. Why do we need any end play at all? Why dont we set then up with preload using turning torque? Is it because they have grease rather than oil? Is it because of the heat transfer from the brakes? Seems like a bit of preload would work, does anyone know(or have any ideas) why GM specified end play?

RBrid

Me again folks. I have a follow-up question.
I did the other side's setup tonight. I used the new spacer but it turned out that the best shim I could use was the old shim. It gave me an end play of .002". Is it OK to use a 37 year old shim that look fine?
If I can't use it, I have to grind down a new thicker shim. Thanks again.

'75

The age of the shim makes no difference, used or new, and .002 is good to go also.

doorgunner

I'm just a rookie with Corvettes, but have some aviation experience ( besides a machine gun)....I think it has to do with brake heat/weight/side thrust/torque/etc. Think of the rear spindle just as you would a front spindle with the addition of 350 h.p. from the drive-train (which, to me, would require a tighter clearance). BUT.... Trust me that a pre-load would not last ( don't ask).

Also.....Harley Davidson originally set up their bearings on the rear axle of the "heavy bikes" the same way Corvette rear spindles are set up.....with a press fit on BOTH bearings (a secret pre-load if the clearance was set too tight causing early failure/40-50,000 miles!)

H.D. found out that one bearing needed to be a near-slip-fit on the spindle shaft to prevent unwanted binding...the bearings lasted much longer set up that way---that is how I set mine up---I'll let you know in 150,000 miles how it worked for me....LOL.

Mick71

I have over 100k on my '81 Super Glide set up this way, with no problems.

Mike Ward

The quick answer is that tapered roller bearings don't like anything more than minor preload. The rollers MUST be allowed to slip since the circumference of the race at one end is much smaller than the other. Kinda like needing a differential between the rear wheels.

The other factor is that 'cold' clearances are a reverse engineered derivative of what the bearings need to run at when hot. I would presume that GM knew exactly how much the clearances changed as the bearings got up to running temps and specified cold assembly clearances accordingly.

doorgunner

What M.W. said.....

I'm not sure, but I think that even FoMoCo instructions say to tighten the spindle bearing on a car until it is preloaded (the nut stops turning)/THEN...back off the retaining nut a certain amount/number of flats (which is another method of setting end-play) before installing the cotter pin.

RBrid

Thanks '75 and all for the input. It's nice to be able to post a question before going to sleep and wake up the next morning with an answer.

DUB

A rear differential has a crush collar as you know...the rear wheel bearings do not. You can not technically compare the two. Having some end play in the rear wheel bearings is fine and needed. Having '0" end play is something I would not want to do. I still try to get to .001" to .003" max.

Unless you are 'one of those people' who turn the shaft of the spindle down so the bearings are 'slip-fit'...like the front bearings....I guess you could....and it has been discussed before comparing different manufacturers designs and comparing them to the Corvette design.

I myself choose to keep things as designed and not try to 'reinvent the wheel' ore employ other manufacturers ideas (regardless if the ideas are good or not). I have replaced more rear bearings that spun on the spindle shaft and ruined them...so removing this variable 'right off the bat'...is something I can not 'buy into'. If you choose to do so this....that is your decision.

If the factory set-up and design will work for well over 50,000+ miles...why change it?

In my opinion the end play is for the brakes....and as Mike Ward mentioned...expansion of parts when they get hot.

I do not worry about what media of lubricant is being used. When I worked at Fruehauf Trailers a long time ago....when I worked on the axle line putting the bearings, hub/drums or even HUGE 4 piston Corvette style calipers and discs and tires on...some customers ordered oil for bearing lubricant...and then some ordered Lubriplate.

DUB

0Willcox Corvette

A neat tidbit for everyone...

GM tried slip fit bearings in 63, it failed. GM tried friction fit bearings and it too failed.

Below is the final TSB issued June 10, 1963 that dealt with the final changes in the rear wheel bearings. It also includes previous design changes since day one production of the IRS. I wish I had more time to upload all of these bulletins.. I have the full collection from 1958-1988.

The 63 swc we just completed had one side friction fit and the other press fit..

Here, we try to run the clearance between .002 - .004

Corvette Technical Service Bulletin 599 Rear Spindle Change

doorgunner

Now I'm wondering...........

What is the tolerance/clearance they used for the "slip-fit"?

Did they slip-fit BOTH bearings?

Or did they specifically slip-fit ONLY the smaller outer bearing?

( My definition of Slip-fit: the bearing I.D. has to be oiled and pushed on with thumb pressure .0005" clearance between bearing I.D and shaft)

I'm trying to come up with something that will work for everyone.

Mike Ward

GM already did that back in '63 with the revised hardware and assembly procedure. Let's not re-re-re-invent the wheel.

0Willcox Corvette

I have to agree Mike-

Gm tried both designs and both failed. The third design (press fit) has brought 100's of thousands of miles of trouble free driving.