C2-C3 rear spring center clamp plate torque

[R N.]

Hello All,

I've been told by some when replacing the rear spring for C2 & C3's that the center clamp plate with the 4-bolts that holds the spring to the carrier cover should be torqued when the car has weight on the suspension. The shop manual says to "snug bolts to position spring and then torque" while the suspension is hanging.

Is one way better than the other?

[Wayne M.]

Re: C2-C3 rear spring center clamp plate torque

Hello All,

The shop manual says to "snug bolts to position spring and then torque" while the suspension is hanging.

Assembly Instructions Manual (AIM) says to (final) torque [to 55-75 ft.lbs] with spring compressed to design height (which I interpret to mean under the load it would have if the car was fully assembled and the rear supported as in rolling condition).

Never final torque with spring arched and no load, or you'll crack the rear ears on the diff cover.

[Terry M.]

Re: C2-C3 rear spring center clamp plate torque

One way is mucho better -- the other way will/may damage your differential cover.

BE SURE TO TORQUE THE BOLTS WITH WEIGHT ON THE SUSPENSION.

If you torque the bolts with the spring hanging there is a good chance you will break one of the ears off the cover.

ALSO BE SURE THE BOLTS YOU USE ARE THE CORRECT LENGTH. TOO LONG WILL PUNCH A HOLE IN THE COVER, and it will be hard to stop the resultant fluid leak.

There was a recent thread on this forum in which the correct length for those bolts was given.

[R N.]

Re: C2-C3 rear spring center clamp plate torque

Thank you Wayne & Terry. I'll look for that thread on the bolt length because I've believe the vendors selling the bolts offer both for the standard spring and for the F41 spring.

[John H.]

Re: C2-C3 rear spring center clamp plate torque

Chevy didn't bother to put that little tidbit in the Chassis Service Manual until 1971, although it was always in the Assembly Manual.

[Ned T.]

Re: C2-C3 rear spring center clamp plate torque

Any way of putting weight on the chassis that compares to the weight of the car so you can torque the bolts during chassis assembly? How much weight would you need?

[Joe L.]

Re: C2-C3 rear spring center clamp plate torque

Any way of putting weight on the chassis that compares to the weight of the car so you can torque the bolts during chassis assembly? How much weight would you need?

Ned----


The spring needs to be nearly "flat". When you achieve that, you can torque the bolts.

[Joe L.]

Re: C2-C3 rear spring center clamp plate torque

Thank you Wayne & Terry. I'll look for that thread on the bolt length because I've believe the vendors selling the bolts offer both for the standard spring and for the F41 spring.

Kurt-----


While I realize that reproduction sources offer 2 different length bolts, one for the 9 leaf spring and one for the 7 leaf, I have never been able to find any information or confirmation that different length bolts were used in PRODUCTION. The only bolt I've ever come up with is the GM #3833486 for applications using a 9/16-12 bolt size.

[Ned T.]

Re: C2-C3 rear spring center clamp plate torque

Joe, I understand what you're saying. As long as the spring is touching evenly on the differential housing I can go ahead and torque the bolts. You just don't want to use the bolts to draw the spring flat.

Thanks, Ned

[Stephen L.]

Re: C2-C3 rear spring center clamp plate torque

Any way of putting weight on the chassis that compares to the weight of the car so you can torque the bolts during chassis assembly? How much weight would you need?

Ned, when I assembled my chassis I left all the suspension bolts loose (snug) that would require full weight on the suspension, such as, the rear spring mounting and the front "A" arm bushings. I hung a "reminder" ticket front and back to complete the torquing once the weight was on the chassis. This worked for me. These items don't need full torque while sitting in the garage during assembly. The notes were a reminder to torque before driving.....

[Terry M.]

Re: C2-C3 rear spring center clamp plate torque

I guess I could have it wrong, but I always thought the spring stack height for both the 7 and 9 leaf springs were the same, or close to it. The 7-leaf is stiffer because each of the leaves is thicker thus more resistant to flex.

But WTFDIK.

[Joe L.]

Re: C2-C3 rear spring center clamp plate torque

I guess I could have it wrong, but I always thought the spring stack height for both the 7 and 9 leaf springs were the same, or close to it. The 7-leaf is stiffer because each of the leaves is thicker thus more resistant to flex.

But WTFDIK.

Terry----


That's what I think, too. I don't think there's a very great difference in the stack height between the 2 springs.

[Terry M.]

Re: C2-C3 rear spring center clamp plate torque

Which leads me to wonder why the after-market has two length bolts for this application.

Maybe it is like the right angle tach-drive unit that goes on the distributer. A useless part if one installs the distributor correctly. A part to solve a problem that shouldn't exist.