Rear Leaf Spring - 10 Leafs

[Vincent D.]

I'm rebuilding my rear suspension and everything is removed and getting rebuilt by Gary R/restored by me. Just took the spring apart to sand blast it and discovered there are 10 leafs so I'm gussing that its some after market spring. Funny though everything is painted gray and all leafs have the slightly curled ends; they're all arched, the shorter pieces very slightly. I've had it out about 3 weeks and never noticed it had 10 leafs. Does it make sense to use it with 9 leafs? I'm guessing not. Seems that Eaton Spring is the place to buy from reviewing libraray threads.
Thanks,
Vin

[Edward J.]

Re: Rear Leaf Spring - 10 Leafs

Vincent, There were some posts recently about about replacement 10 leaf springs and I believe that there were a later Gm replacement.

They don't recommend removing any springs to make a 9 leaf, this will change the spring rate.

[Timothy B.]

Re: Rear Leaf Spring - 10 Leafs

Vincent,

The GM replacement spring I bought for my 63 Corvette back in 1980 had 10 leafs. The ride height is very good not high like these repro springs.

Somewhere in the archives there is info with part #'s and years that Corvette actually used this spring. I believe it is 75 up but not sure, I see no problem using it.

By the way, this spring used some sort of metal liner not the black plastic liner. Very nice spring..

[Gary B.]

Rear Leaf Spring - 10 Leafs

Vincent,

The first article I wrote for the Restorer about 8 or 9 years ago listed the different standard Corvette leaf springs used in production between 1963 and 1977. According to my research for that article the standard spring for 1976-1977 was GM part # 362153, which was a one-stage spring (all leaves arched) with 10 leaves and 9 liners. I suspect that standard 10-leaf spring became the service replacement part until it was eventually replaced with the HD spring as the service replacement part.

Gary

[Vincent D.]

Re: Rear Leaf Spring - 10 Leafs

Thanks everyone! Along with the 10 leafs there are 9 liners. The liners are black plastic not metalic. There were no stamped numbers on any of the leafs, however, there was a stenciled (looked white) on the longest leaf...the number is 21-225 if that means anything. All leafs have a small flare on the ends as well as the slight curl. The car sat a little (very little) low in the rear before I took it apart. For now I'm thinking of putting it back, see how it sits and driving the car while looking around for a good used original. I'm tring to do everything NCRS correct when I touch something. How much of a deduction would there be for this 10 leaf spring/

Thanks again everyone,
Vin

[Gary B.]

Rear Leaf Spring - 10 Leafs; 21-225 = SRI #

Vincent,

I believe the 21-225 is the Spring Research Institute number for that Corvette leaf spring. I've always thought the SRI number would not appear on an original GM item, but I'm not 100% certain that is correct. I just don't know if GM would allow a vendor to put the SRI number on a spring sold by GM.

Anyone know what GM would and wouldn't allow in terms of marking such parts with non-GM numbers? John Hinckley? Joe Lucia? Michael Hanson? Others in the know? Anyone know the GM policy?

Gary

[Ronald L.]

Re: Rear Leaf Spring - 10 Leafs

Gary,

Putting their logo and trade marks on an OE part or specifications?

For sure in the 60's and 70's we have supplier logo's on many GM parts.

As far as specifications, depends on the parts. If it has to do with lighting and FMVSS - each lamp is identified by the cavity of the mold it came out of and the cert numbers. Fuel tanks have to be tracked to a central NITSA data base, they are "today" serialized.

Springs would not be the type of item that would seem to require this, I've seen the part number painted on, can check a few NOS springs if we know what to look for.

[Gary B.]

Re: Rear Leaf Spring - 10 Leafs

Ron,

Numbers like 21-225 and xx-307 (if I remember correctly) have been reported on some leaf springs on Corvettes from the 70s. The question is, are those springs original GM springs, or have then been replaced sometime during the intervening years. In my opinion repro springs are likely to have the SRI #, since spring manufacturers typically are members of the SRI organization in order to have access to the specs for a given spring. It makes sense the spring vendor would then label the spring with the SRI #. That's why I always assume springs with the SRI # are repro springs. But that's just been a supposition of mine and it may not be correct.

Gary

[Gary B.]

SRI #s: 21-225; 21-307

Ron,

I have notes that two SRI #s for Corvette leaf springs are 21-225 and 21-307. Unfortunately, I don't have a record of which GM springs these correspond to.

Gary

[Gary B.]

Rear Leaf Spring; SRI #s -> GM #s

Ron,

A vendor website (sdtrucksprings.com) gives the following SRI #s for 63-77 Corvette leaf springs:

21-307 3850839 9-leaf; two-stage

21-225 3794095 9 leaves; single stage

21-227 382881 7 leafs; two-stage

A 7-leaf, two-stage spring is not a beast I'm familiar with. As far as I know all HD (7-leaf) Corvette springs were single stage.

In any case, does anyone have an known original GM leaf spring with any of the above three SRI numbers stenciled on the spring?

Gary

[John H.]

Re: Rear Leaf Spring - 10 Leafs

The only leaf springs I've seen with SRI numbers on them also carried the stenciled "JRS" letters (for John R. Spring Service, Warren, Michigan); they've been making replacement/reproduction leaf springs for decades.

[Gary B.]

Re: Rear Leaf Spring - 10 Leafs

John,

Do you think it's possible there was a vendor who made service replacement springs for GM who put the SRI # on springs that GM sold over the counter?

Gary

[Ronald L.]

Re: Rear Leaf Spring - 10 Leafs

Gary, I seem to recall seeing that on service parts. A print would tell us the requirements for the OE part supplied to St Louis.

[Douglas L.]

Re: Rear Leaf Spring - 10 Leafs

Gary,

Here are some pics of a 10 leaf rear spring that came out of an early 67 coupe. The spring is still together. I can find no stamps or numbers on the exposed leafs. The only thing that is obvious to me is the center bolt looks original and there is evidence of the original gray paint. Would the over the counter replacement be gray or were they black or non-painted?

[Ronald L.]

Re: Rear Leaf Spring - 10 Leafs

The GM service parts into the 80's were still painted gray. Here is a F41 with the part number stencil. These GM parts plant that stocked these was Lansing.