rear spring bolts

[Tom Sarno]

I was going to reinstall the bolts from the trailing arms to the spring when I noticed that one was 6 inches overall length and the other was 6 5/8 inches overall. Are these bolts from two differant years/cars or are they supposed to be unequal length?

Also, what are the torque specs for the spring to cover bolts?

Thanks for all the help.
Tom

[Joe L.]

Re: rear spring bolts

Tom---

The original bolts used from 1963 through 1972, GM #3831585, was 6-1/2" overall length. After 1972, several different bolt lengths were used in order to ensure that rear bumper height would fall within tight specs for federal crash requirements. None of these special bolt lengths were ever available in SERVICE, though.

The current GM SERVICE spring bolt for all 63-75 applications is GM #458982. This bolt is spec'ed out at being 6-1/2" long. However, I've measured some that were as short as 6-5/16". The important dimension is the length of the shank from the bottom of the bolt head to the top of the threads. This should be the same for both bolts that you use. If the thread length is a bit different between bolts, that should cause no problems, at all, except for possible problem with cotter key alignment with the castle nuts you use.

[Joe C.]

Re: rear spring bolts

Tom:

Very possibly intentionally done to even out any yaw at the rear of the car. If your car sits straight now, then if you use equal length bolts, the car will lean to stab'd or port.

Joe

[Tom Sarno]

Re: rear spring bolts

Joe,

You are right, someone probably did it intentionally to compensate for a bad spring. The whole car was just put together wrong. It appears that someone combined the rejected parts from other projects to build my car. There is a mix of years, parts missing and some modified to work with broken parts. That's why I always ask how it should be, and not go be the way it was removed from my car.

I wish I had spent time on this board before purchasing my first Corvette.

Thanks
Tom

[William C.]

Re: rear spring bolts *NM*

[Greg A.]

Re: rear spring bolts

Joe, any thoughts on where to locate shorter spring bolts. I've been trying to even out the ride height on my '78 after having a couple different rear springs installed. I noticed in the AIM that different bolts were possibly used to correct this at the factory, but my efforts at salvage yards have yielded zip. I probably need two 6" bolts to do the job. Thanks.

Greg.

[Joe L.]

Re: rear spring bolts

Greg------

I'd be reluctant to use used bolts for this application. These bolts should be changed every time that they're removed. However, I don't know where to get bolts of different lengths. As I mentioned, these non-standard length bolts were never available from GM.