Re: 1928 Front End Shimmy

Posted by DavidPackard On 2022/7/17 20:08:13

Gar;

In the ’29 service manual page 221, there is a ‘cut-away’ of the front suspension and steering knuckle. That graphic suggests the Packard ‘Steering Knuckle Pin’ features ball bearings that require some type of shimming. The adjustment procedure is on page 222, procedure S119. The material call-out mentions shims of 0.005” or 0.025” thickness. All of this suggests either a minimum vertical motion or bearing pre-load is being set. I’m significantly out of my league with that design . . . I’m strictly from reamed Bushingville, with a simple thrust bearing to support the weight of the car.

The note in S119, step #5 suggests a check should be made to ensure the bearings have not been pinched with excessive preload, therefore if you use the procedure to check the bushing design a near zero ‘looseness’ would be expected. The contents of Technical Letter 1840 (referenced in S119) may contain the missing pieces, but I’ve been unsuccessful finding that document. Assuming this site has a copy, I think I need HH56’s site navigation skills.

Update: I finally found TL 1840. I'll look it over for some insight on the adjustment "do's and don'ts".

Seems the bearings were being ‘pinched’ in the field by not shimming correctly (still no insight on the correct procedure). The fix was a different plug, and two Belleville washers to replace the stack of shims. Seems the new plug could be made locally by machining the original design. All of that detail tells me the bearings were designed for a preload (zero slop), but the field exceeded the desired pre-load while maintaining the cars.

Gar, download a copy of Technical Letter 1840 and measure your cap against the 13/32 dimension called-out in the letter. If it’s 3/16 longer, then you have the original design. Still no idea of the Belleville geometry.


dp