Tightening C3 rear spring shackle bolt

[Tom M.]

I'm replacing my rear spring shackle bolts and cushions with new stuff from one of the usual vendors. There is a shoulder on the bolt that I thought should be where the nut bottoms/tightens. But, if I tighten the nut against the shoulder the cotter pin holes for the castle nut are way below the nut. So, the nut is now backed off and the cotter pin is what secures the nut in place. In other words, the nut is floating on the bolt.
This just doesn't seem right. Are the bolts incorrectly drilled? Or should the nut just be threaded to the point where the cotter pin is the only thing that keeps it from spinning?

[Joe L.]

Re: Tightening C3 rear spring shackle bolt

I'm replacing my rear spring shackle bolts and cushions with new stuff from one of the usual vendors. There is a shoulder on the bolt that I thought should be where the nut bottoms/tightens. But, if I tighten the nut against the shoulder the cotter pin holes for the castle nut are way below the nut. So, the nut is now backed off and the cotter pin is what secures the nut in place. In other words, the nut is floating on the bolt.
This just doesn't seem right. Are the bolts incorrectly drilled? Or should the nut just be threaded to the point where the cotter pin is the only thing that keeps it from spinning?

Tom------


The nut should be turned down to the point that the cotter pin hole in the bolt aligns with a slot in the slotted nut. Then, insert the PROPER SIZE cotter pin, bend and you're done. The proper size cotter pin is 1/8" X 1-1/4".

[Tom M.]

Re: Tightening C3 rear spring shackle bolt

Thanks Joe,
Thats how I have it set up now. It just didn't seem right to not have the bolt torqued to a shoulder like the ones I removed (had to cut them off) But then again, if it works for wheel bearings...

getting closer to driving-the roads are empty....

[Joe L.]

Re: Tightening C3 rear spring shackle bolt

Thanks Joe,
Thats how I have it set up now. It just didn't seem right to not have the bolt torqued to a shoulder like the ones I removed (had to cut them off) But then again, if it works for wheel bearings...

getting closer to driving-the roads are empty....

Tom------


Were the nuts you removed torqued with the nut on the shoulder of the bolt or just frozen due to corrosion? If the former, the guy that installed them didn't know what he was doing.

[Tom M.]

Re: Tightening C3 rear spring shackle bolt

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Joe, about 99% probable these were installed by GM. They may have only been rust frozen but here's a shot of what was removed. I ended up cutting them both off. They are the first bolts that I have ever had to cut during the past 25 years.

[Joe L.]

Re: Tightening C3 rear spring shackle bolt

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Joe, about 99% probable these were installed by GM. They may have only been rust frozen but here's a shot of what was removed. I ended up cutting them both off. They are the first bolts that I have ever had to cut during the past 25 years.

Tom------


From what I can see, it looks like the cotter pin was properly installed. So, the fact that the nut was down against the collar at the end of the thread is not really too significant; that could happen. However, I highly doubt that the nut was actually torqued down. I fully expect that the difficulty in removal was due to corrosion. From what I can see of the bolt it looks like it suffered significant corrosion damage.

By the way, GM advised that these bolts were to be replaced whenever they were removed for any reason. Another interesting "factoid": the bolts were material grade GM 290M indicated by 5 radial lines on the head. As far as I know, these are the only bolts of that material grade used on a Corvette.

[Tom M.]

Re: Tightening C3 rear spring shackle bolt

image.jpg
SBC bolt