Rear Spring/Trailing Arm Rubber Cushions... GM or Aftermarket???

[Joe L.]

Re: Rear Spring/Trailing Arm Rubber Cushions... GM or Aftermarket???

All-----

I dug out some of the GM #3831586 cushions from my collection. I have some that are from the late 60's-early 70's period (based on the packaging and labeling style). I also have some that are from much more recent vintage, probably from the last 2 or 3 years. For all practical purposes, they are identical. Both measure 1.98" at the base. The older examples measure 1.22" in total height (including height of the spring locating extension). The newer measure 1.24". The older examples have more mold flash at the base and at the extension but both are insignificant from a functionality standpoint.

Most of the aftermarket cushions I have seen on the market are polyurethane. I would NEVER use them.


DSCN4241.jpgDSCN4242.jpgDSCN4243.jpgDSCN4244.jpg

[Gary B.]

[Thomas B.]

[Don H.]

Re: Rear Spring/Trailing Arm Rubber Cushions... GM or Aftermarket???

When you replace them, flip over the heavy support washers.. The rounded shoulder goes towards the cushion.. As you have them now, the sharp edge will cut into the cushion..

[Jack M.]

Re: Rear Spring/Trailing Arm Rubber Cushions... GM or Aftermarket???

Indeed, Don... a VERY common mistake (especially when people go by 'looks').
The AIM does call it out the retainer placement... and also I'll include a Corvette News image.

Rear Spring Retainer - 1967 Corvette Assembly Manual-01.jpg
Rear Spring Retainer - 1967 Corvette Assembly Manual-02.jpg

Rear Spring Retainer - 1963 Corvette News Supplement.jpg

[Thomas B.]

Re: Rear Spring/Trailing Arm Rubber Cushions... GM or Aftermarket???

Thanks, guys, I did not notice that. Will correct that when I replace the cushions.

[Keith M.]

Re: Rear Spring/Trailing Arm Rubber Cushions... GM or Aftermarket???

I woulda thought they would go the other way. So...good to know.

[Gary B.]

Re: Rear Spring/Trailing Arm Rubber Cushions... GM or Aftermarket???

Others have made that same mistake, and others will continue to make that mistake, since the correct orientation seems backwards. Until you understand why it’s done that way.

Gary

[Keith M.]

Re: Rear Spring/Trailing Arm Rubber Cushions... GM or Aftermarket???

Others have made that same mistake, and others will continue to make that mistake, since the correct seems backwards.

Gary

100% IT seems totally counterintuitive.

[Leif A.]

Re: Rear Spring/Trailing Arm Rubber Cushions... GM or Aftermarket???

There was a great discussion about trailing arm washer orientation and rear lower shock absorber washer orientation on the CF back in February. There was, ultimately, an engineering explanation as to why the washers are oriented they way they are.
Reason:
"Be sure to note the orientation of the washers (cup side facing away from bushing) and the size of inside diameter. If over compressed, the bushings will constrict the movement of the shock absorber with the articulation of the suspension and put excessive side loading on it. This restricted movement (side loading) will cause premature rod seal failure, resulting is oil leakage or metal fatigue to the shock absorber end mount."
The same articulations apply to the spring end bushings.
Here's the CF discussion for anyone interested.

https://www.corvetteforum.com/forums...direction.html

[Joe L.]

Re: Rear Spring/Trailing Arm Rubber Cushions... GM or Aftermarket???

Zip Products has the rubber ones and the polyurethane in stock. The rubber ones look similar but not identical to the NOS posted above. I’m guessing the poly ones would result in a harder ride. Zip claims better steering response with the poly ones. Zip includes an article from Corvette Magazine regarding rebuild of rear suspension including the spring cushions. The article shows the rubber cushions being installed. Looks like mine are due for replacement. I’ll probably go with rubber when I replace mine. Keep it stock and correct as possible.

Thomas------


In addition to the incorrect retainer installation, the slotted nuts seen in this photo are not the correct configuration.

[Patrick H.]

Re: Rear Spring/Trailing Arm Rubber Cushions... GM or Aftermarket???

Thomas------


In addition to the incorrect retainer installation, the slotted nuts seen in this photo are not the correct configuration.

And there's way too much black paint on everything. Very few items in the picture were actually black on Day 1.

[Thomas B.]

[Joe L.]

Re: Rear Spring/Trailing Arm Rubber Cushions... GM or Aftermarket???

Yes I agree. Car was restored in the mid to late 80s with only 1800 miles added since. Previous owner was more concerned with chassis corrosion than factory originality. Underside of body is painted which is also incorrect. I’ll look into correcting the slotted nuts as well as the cushions. Thanks.

Thomas-------


There's definitely something to be said for corrosion protection. I'm an "I-hate-rust" guy myself. However, use of a satin clear can be equally protective.

By the way, I should have mentioned that while the slotted nuts are of incorrect configuration, I use that style myself. This style nut has a larger bearing surface on the retainers than the original style nuts. So, while incorrect, I believe that functionality is improved.

[William F.]

Re: Rear Spring/Trailing Arm Rubber Cushions... GM or Aftermarket???

Well other than searching for some possibly dried out NOS cushions where is the best source for new rubber ones? ZIP which the "DR." always criticized?