Uhhh. once every 5 years is too onerous a task?

 

Yep. (I learned those one-word answers from you )

Anyhow.....as a machinist I was asked to modify industrial equipment that used grease in the bearing housings. I used tungsten carbide drills (bits) to drill through bearing races/tap housings for fittings....I know that you know a bearing takes very little grease (it would take a lifetime to fill a bearing support with grease to the point the seals blew out). I also converted (greased) housings to oil bath housings. And it's not that difficult.....takes about the same amount of time to do the mod as an onerous task would take.

As for having to "do it" every five years.....my '41 pickup had grease fittings on the waterpump/oil cups on the generator which required monthly greasings/oil re-fillings.......somewhere along the line some lazy individual got the idea to make sealed bearings....(I guess monthly was too often). The engine still had the crank-handle though.....which I had to use about every five years until I replaced the worn-out battery .

I'm sure that you guys have learned/applied some changes/shortcuts in your lives.....that's why rookies like me appreciate your help.

By the way.....thanks to you guys encouraging rookies to get some hands-on experience, I now can have a trailing arm on the workbench in less than an hour.....(hmmmmmm....many every 5 years isn't so onerous a task after all colonD )

 

Perhaps it's the engineer in me, but I'm not comfortble with some of the simple answers/speculation thrown out here (from multiple posters).

I don't agree with an earlier comment that the original suspension designers just did a dumb "copy and paste" off of the front suspension. There's multiple design differences between the front and rear assemblies. Those guys aren't/weren't idiots, and I suspect that Duntov peered over the designers shoulders on occasion.

I don't agree with the inner/outer cylinder analogy above. The bearing races are not just floating there helter-skelter. Remember that both inner bearing races are "pressed" together via the force of the spindle nut torque, through the spacer and shim, and then the outside bearing gets forced/pressed against the fillet area of the spindle. Nothing's just "floating around" if it's manufactured correctly.

It's mentioned by a poster here that racers use a slipfit on their spindles for easier maintenance. The rigors of racing are much harder on bearings than a street car sees. Why would they (racers) risk a DNF just for ease of working on their car if slipfit was an issue? (Not a recommendation, just an invitation for additional insight.)

I'm curious if the press-fit change was a cure/bandaid for an unknown driving cause, or a bandaid for some unexpected tolerance/slop experienced during high volume manufacturing. Sometimes things work just great on the proving ground, and the problem never shows up until there's a bunch of vehicles getting miles on them.

Just curious, has there ever been an actual description from Chevrolet on what the actual failure cause (not result) is?

 

There's no speculation in any of my statements. The failure mode was common knowledge at GM during the era. The opening statement in TSB DR#599 issued June 10 1963 confirms it.

Do you understand that the inner races move radially with respect to the spindle as the latter rotates?

 

Here is my opinion on the GM change/TSB. I think the initial slip-fit set-up was done that way for ease of serviceability but that service rarely occurred. If people had taken it apart and re greased if regularly as GM wanted them to there most likely wouldn't have been too many problems. I think the issue was that recommended service rarely happened and lack of lubrication caused bearing failure leading to spindle wear and in some cases spindle failure. In my opinion, GMs solution was to press fit the bearings on the spindle so the in most cases the worst that would happen is bearing failure. Point is, I believe the change wasn't there to correct a design flaw but rather to eliminate problems caused by ignoring service intervals.

 

The TSB was introduced barely a year after the first C2 rolled off the assembly line, long before any servicing would have been required on even the earliest cars.

 

Thats quite a presumptuous statement, how do you know?

 

The bulletin introducing the final fix was issued June 10th 1963 after several months of investigation and development. The cars were introduced in September '62. How many miles do you believe each car was driven in that short period of time?

 

AS YOU SHOULD NOT AGREE,,,,BUT...what you failed to do is UNDERSTAND the 'inner/outer cylinder' analogy. You are thinking about it incorrectly. The inner cylinder is the SPINDLE...and the outer cylinder's INNER SURFACE is the inner bearing surface THAT WOULD BE PRESS FIT ON to a spindle....but in Mikes comment...is showing how if it were SLIP FIT...you WOULD have a problem. Has nothing to do with the races. So the OUTER CYLINDER's INNER SURFACE can spin and slip against the INNER CYLINDER's OUTER SURFACE..

SO..having the NUT tight...holding the bearing tightly together....THE INNER surface of the SLIP FIT bearing can spin against the spindle....THAT IS THE ISSUE.

Just because they do it...and maintain it...does not make IT right. If it works and they have no problems...I guess they would stick with it. BUT it is FUNNY HOW no one will talk about how many spindles have been broken on the race track due to potential heat in the area where the parts can spin against each other....WE all know...'they' do not want to talk about that. JUST SAYING. I have seen some crazy thing racers do that I would NEVER do on a street car.


ONCE again....it is NOT an unknown driving cause....this has been explained before. AND is NOT a 'Band-Aid'. From 1963 to 1982 over 633 thousand cars were built that used press fit rear wheel bearings.. I think GM had it figured out well.

It is KINDA funny that on the SAME axis...the differential carrier bearings are PRESSED onto the carrier assembly inside the differential. MAYBE GM went with this method of PRESS FIT for the wheel bearings...AFTER the slip fit showed to be a problem that they fixed. One again...Mikes analogy makes sense.

I think Mike has given the information to why the change was made. With you being an engineer( not knowing actually what field)...you should hopefully be able to realize that....and with my past posts clearly describing that even with the pressed on bearings beginning to spin on the shaft of the spindle and damaging it that I have serviced.....when it started out being PRESS FIT....COMMON SENSE would dictate that starting off with a SLIP FIT. Is just asking for trouble....UNLESS a person maintains it....BUT...STILL the PROBLEM is there from the beginning.

You are aware that rod and main bearings of an engine are 'locked' into place...so-to-speak and DO NOT TURN because of the rotating parts that spin against them.....HENCE on how bad it is to have s SPUN rod/main bearing. The concept is different...but it is basically NO DIFFERENT. And how important the clearances are when building an engine for what it is being used for...for the oil to protect and cushion this area....so-to-speak.

The wheel bearing being pressed onto the spindle....the inner surface of the bearing DOES NOT SPIN differently than the spindle. THEY ARE ONE. The roller tapered bearings can spin....and the OUTER RACE stays still due to being pressed in place...the grease and set-up on the bearing is like the engine rod/main bearing clearances where oil would normally go. SO you only have ONE part able to move independently. That part being the tapered roller bearings....which is like the OIL in the rod/main bearings.

I know this was be stretch ...but I do not know what else to do other than to advise you to contact a University that has a automotive design department and talk to an engineer that KNOWS this area. I KNOW you can ask questions...and BUT I can not help you any further.

DUB