C3 - Leaf Spring Question

[Jim Markevitch]

I have a question with regards to the rear leaf spring on my 72. Where the plate that bolts into the differential and holds the leaf spring in place there are two L-shaped brackets attached. They are at least ¼” thick and have two holes in each. My question is what are/were these used for? I looked through my assembly manual, maintenance manual, and could not find a reference to them. Do they need to be there?

[Joe L.]

Re: C3 - Leaf Spring Question

Jim-----

First, a question for you. What is the size of the 4 bolts that attach the spring plate to the differential cover and what is the casting number of your differential cover?

All 1963-77 Corvettes used a spring which was 2-1/4" wide and the bolts attaching the spring retainer plate to the cover were 9/16" (11/16" across the flats or wrench size). These bolts were used in conjunction with differential cover casting #3871375 (GM PART #3871374) which was drilled and tapped for the 9/16" bolts.

In 1978, Corvette spring size changed to 2-1/2" wide for many applications. A change was also made to the differential cover, spring plate and bolts. The differential cover was changed to casting #464910 (GM PART #464909). This cover utilizes spring retaining bolts of 7/16" (5/8" across the flats or wrench size).

In July 1981, the GM #3871374 cover was discontinued from SERVICE and replaced by the GM #464910 for SERVICE of all 1963-79 Corvette applications. When this cover is used for 1963-77 SERVICE applications or 78-79 applications using a 2-1/4" wide spring, then 2 spacers GM #459032 must be used between each set of spring bolts and the spring. Also, 7/16" spring bolts and spring retaining plate GM #457977 with 7/16" holes must be used. The GM #459032 spacers generally are configured like the pieces which you described.

So, if you have the GM CASTING #474910 cover and 7/16" spring retaining bolts, then your original cover has been replaced and that's why the need for spacers which you described. Otherwise, I don't know what the parts that you described could be.

[Frank H.]

Re: C3 - Leaf Spring Question

It maybe from a center mounted aftermarket traction bar,once widely used ,a real speed bump scraper,their may be two more mounts bolted or welded forward at the crossmember that the front of the traction bar mounted to,and held the rear case from twisting on hi torque loads.

[Jim Markevitch]

Re: C3 - Leaf Spring Question

Frank.......... That sound like it. It's coming off as it serves no purpose.

Thanks