Rear leaf clamp bolts punching thru diff

[Steve L.]

It seems like the bolts are too long. My leaf spring is a combination of original leaves and repo leaves. The thickness of this combo is 3.22inch.

When I take the bolt (Paragon original leaf spring 3 9/16 bolt length) and screw it into the diff to bottom it out without the spring, measure the spring seat to bolt head, then subtract the spring plate, lockwasher and spring thickness, I get a clearance of around 3/8 inch.

It looks like I need to shorten the bolts by around 1/2 inch.

Am I missing something here. I don't want to punch a hole through the diff when I torque it down.

If I remember correctly, I think my original bolt was 3 1/2 inch long.

This is for a 73

[Paul O.]

Re: Rear leaf clamp bolts punching thru diff

Steve if you move to the bottom of the page of your thread there are some archived threads that may help.. There is one there that Joe Lucia responded to here is a copy of that if you look there are 11 responses to that thread.

Steve------

All 1963-77 Corvettes originally used spring retainer bolt GM #3833486. This bolt was a 9/16-12 bolt of 3-7/32" long. It was a special GM 280M (SAE Grade 5)bolt in that it had a non-standard shank-to-thread length. Since the shank of the bolt "aligns and locates" the spring, in this configuration, a minimum of threads were in contact with the spring.

The GM #3833486 bolt was GM -discontinued many years ago and replaced by GM #9428598. This bolt is a GM 300M bolt (SAE Grade8) more-or-less standard shank-to-thread configuration. It has a total length of 3-3/4" and a thread length of 1-3/8". Unfortunately, it's been discontinued, too.

I don't understand how a bolt that is about 1/2" longer than the original was used as a replacement, especially in this situation in which bolt length is somewhat critical. However, I can tell you that either of these bolts will work just fine with a spring of ORIGINAL THICKNESS.

Hope this helps always check the Threads at the bottom of the page there maybe help there.

Paul 18046

[Steve L.]

Re: Rear leaf clamp bolts punching thru diff

The 3 7/32" looks more reasonable to me. If using the Paragon 3 9/16", these springs have gotta be loose?? or you punch through the diff. housing

I just don't undrestand this.

It's even worse if you buy the Paragon 4 inch bolt that is slated for repo springs.

[Wayne M.]

Re: Rear leaf clamp bolts punching thru diff

. ....Am I missing something here. I don't want to punch a hole through the diff when I torque it down.

If I remember correctly, I think my original bolt was 3 1/2 inch long...

Steve -- you can probably find the correct length from the previous threads suggested by others, at the bottom of the page. Here's a pic of an original; I believe there's only about 10 effective threads, which prevents over-insertion.

P.S. I see you're from the Ottawa region. About 20 years ago I did an Ontario search and got a name and address in that area for my first car, a '65 convertible VIN 04835. Originally white/tan, but apparently painted red. If you know of this car, I have some documentation for the current owner.

[Jim B.]

Re: Rear leaf clamp bolts punching thru diff

It seems like the bolts are too long. My leaf spring is a combination of original leaves and repo leaves. The thickness of this combo is 3.22inch.

When I take the bolt (Paragon original leaf spring 3 9/16 bolt length) and screw it into the diff to bottom it out without the spring, measure the spring seat to bolt head, then subtract the spring plate, lockwasher and spring thickness, I get a clearance of around 3/8 inch.

It looks like I need to shorten the bolts by around 1/2 inch.

Am I missing something here. I don't want to punch a hole through the diff when I torque it down.

If I remember correctly, I think my original bolt was 3 1/2 inch long.

This is for a 73

I bought the paragon "exact replacement" bolts for my 68 and they were indeed too long. I had to reuse my old ones which were probably better anyway.

[Steve L.]

Re: Rear leaf clamp bolts punching thru diff

Looks like I'll be shortening my Paragan (original spring ) bolts to 3 7/32 inch long. My originals are too far gone.