Rear Suspension question (spindles/trailing arms) - bearings automatically disturbed?

[Duke W.]

Re: Rear Suspension question (spindles/trailing arms) - bearings automatically distur

Steve,
That 1963 shop manual is not as wrong as you think. The early 1963s did have a slip fit shaft, and since I believe the shop manual was written either before production or early in production -- it is correct for its time. I have no doubt someplace in the information supplied to the dealers and/or mechanics at the time is the information about the revised press fit of the axle shaft, but the shop manuals were never revised. This is also the case for other production running changes in other years. The service manuals rarely catch up with the production changes. This is one of the major reasons that newly revised NCRS TIM&JG now have copies of Service and Information Bulletins as well as Corvette related items from Chevrolet Service News as these were the main sources of information abut running changes back in the day.

That early "slip-fit" design had a lot of failures. There were a couple of interim production changes and IIRC the final press fit design went into production about Dec. 1.

Also, with implementation of the press fit design, the 30K maintenance requirement was eliminated. All of this is documented in a TSB, but GM never thought about these becoming collector cars that would survive for decades, so it's a good idea to rebuild the rear bearing pack every 30 years or so assuming a few thousand miles per year mileage accumulation.

Duke

[Steve G.]

Re: Rear Suspension question (spindles/trailing arms) - bearings automatically distur

That early "slip-fit" design had a lot of failures. There were a couple of interim production changes and IIRC the final press fit design went into production about Dec. 1.

Also, with implementation of the press fit design, the 30K maintenance requirement was eliminated. All of this is documented in a TSB, but GM never thought about these becoming collector cars that would survive for decades, so it's a good idea to rebuild the rear bearing pack every 30 years or so assuming a few thousand miles per year mileage accumulation.

Duke

Interesting. I have never encountered a slip fit arrangement. I'd be curious to know the specifics of the more frequent failures. It's hard to imagine how the fit of the bearing on the shaft could reduce failures.

I have often puzzled over why they are a press fit. They are unlike frt spindles in that the inner races of the bearings along with the spacer and the shim are securely tightened to the shaft with the nut. Certainly pressing them on locks them from turning even more so, but in the world of shafts and bearings and comparing to frt spindles that seems excessive. And how would that prevent bearings from failing?

My unproven theory was that the reason for it was similar to the reason for tapered studs in tie rod ends and ball joints. In the event of loss of the nut, or even breakage of the shaft at the yoke, you will not lose the wheel. As with all the front end components. Remove the nut and you're still a long way from losing the connection.

In these old cars I would be less concerned about how many miles you put on and more concerned with now many years they sit. The grease dries out and gets hard over the years and won't flow into the bearings. I used to have a tool that you secured in place of the yoke that had a grease fitting that would allow you to add fresh grease. That may be an alternative to complete disassembly for service.

[Patrick B.]

Re: Rear Suspension question (spindles/trailing arms) - bearings automatically distur

Interesting. I have never encountered a slip fit arrangement. I'd be curious to know the specifics of the more frequent failures. It's hard to imagine how the fit of the bearing on the shaft could reduce failures.

I have often puzzled over why they are a press fit. They are unlike frt spindles in that the inner races of the bearings along with the spacer and the shim are securely tightened to the shaft with the nut. Certainly pressing them on locks them from turning even more so, but in the world of shafts and bearings and comparing to frt spindles that seems excessive. And how would that prevent bearings from failing?

My unproven theory was that the reason for it was similar to the reason for tapered studs in tie rod ends and ball joints. In the event of loss of the nut, or even breakage of the shaft at the yoke, you will not lose the wheel. As with all the front end components. Remove the nut and you're still a long way from losing the connection.

In these old cars I would be less concerned about how many miles you put on and more concerned with now many years they sit. The grease dries out and gets hard over the years and won't flow into the bearings. I used to have a tool that you secured in place of the yoke that had a grease fitting that would allow you to add fresh grease. That may be an alternative to complete disassembly for service.

I had also been under the impression that the press fit to the rear bearings was a measure to prevent wheel loss in case the spindle broke at the splines. This could have been important on drum brake cars, but the later disc brakes would retain the wheel even without a press fit on the bearings. Therefore, polishing the spindle bearing seats on the disc brake cars for reduced press forces and easier disassembly did not seem like a bad idea.

[Michael W.]

Re: Rear Suspension question (spindles/trailing arms) - bearings automatically distur

The original design could allow lateral movement of the race on the spindle as the latter rotated. This movement could lead to lead to heat, wear and the eventual failure of the bearing assembly which in extreme circumstances, a fracture and release of the spindle itself.

This type of lateral movement of the race does does not occur on front wheel bearings as the spindle does not rotate.

The final fix introduced a tight fit bearing assembly and and an increased torque on the spindle nut which could be regarded as belts and suspenders but it put an end to that type of bearing issues.

GM reintroduced the bearing inspection interval of around 30K miles somewhere in the late 70s to address the old dried, grease issue. There have been several tools introduced over the years in an attempt to circumvent the recommend disassembly but these do NOT allow the outer bearing to be greased adequately without flooding the entire cavity.

[Steve G.]

Re: Rear Suspension question (spindles/trailing arms) - bearings automatically distur

I had also been under the impression that the press fit to the rear bearings was a measure to prevent wheel loss in case the spindle broke at the splines. This could have been important on drum brake cars, but the later disc brakes would retain the wheel even without a press fit on the bearings. Therefore, polishing the spindle bearing seats on the disc brake cars for reduced press forces and easier disassembly did not seem like a bad idea.

That would make perfect sense to me. And they may not have gone back to the slip fit design after the implementation of disc brakes to ensure that the interchangeable spindle didn't make it onto drum brake cars.

They may also have retained the press fit in disc brake cars because relying on the caliper to stop the wheel may have resulted in the wheel locking up which would adversely affect control.

[Michael W.]

Re: Rear Suspension question (spindles/trailing arms) - bearings automatically distur

That would make perfect sense to me. And they may not have gone back to the slip fit design after the implementation of disc brakes to ensure that the interchangeable spindle didn't make it onto drum brake cars.

They may also have retained the press fit in disc brake cars because relying on the caliper to stop the wheel may have resulted in the wheel locking up which would adversely affect control.

It's still possible to have a wheel release with a disk brake car. Lots of neglected C3s have been passed by their own rear wheels on the highway.

GM TSB DR#599 issued June 10 1963 details the change over extensively and is a good read. I think I've posted here on the site.

[Rich C.]

Re: Rear Suspension question (spindles/trailing arms) - bearings automatically distur

Kyle,

Call Gary Ramadei, you'll be happy you did. I brought my trailing arms to him, he disassembled mine right in front of me...very informative, he knows these things inside out.


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