1963-1967 jack spring assembly

[David L.]

I was recently looking on Ebay and found someone selling a NOS 63-64 Corvette jack spring with the single hook. I emailed the seller and got dimensions of the spring part, 5 1/4" O.L. and 4 1/4" coil length. I do not know where the seller got the single hook part but the spring part is probably from a NOS 1969-up Corvette spring assembly, GM # 3963108.
Picture below are 3 different Corvette jack springs in my collection.

1963-1964 single hook, 4 1/2" O.L., 3 1/2" coil length, about 54 coils, GM # 3785772

1965-1968 double hook, 4 1/2" O.L., 3 1/2" coil length, about 54 coils, same GM part # 3785772

1969-up modified double hook, 5 1/4" O.L., 4 1/4" coil length, about 68 coils.

I do not know exactly know when the change from single hook to double hook occurred. My point of this thread is about the spring length but it would be nice to determine when the single to double hook change actually occurred. It's interesting that the part number stayed the same when the single hook was replaced with the double hook.

Dave

[Wayne M.]

Re: 1963-1967 jack spring assembly

......... it would be nice to determine when the single to double hook change actually occurred. It's interesting that the part number stayed the same when the single hook was replaced with the double hook......

Dave --- according to the '65 AIM, UPC 14, Sheet C1, the spring drawing was revised (from single to double hook) and the rubber wrench head boot was added on 10-19-64.

However, they didn't get around to changing the drawing on the 36.5 gal UPC N03, sheet 7, which still shows the single hook.

[Ted K.]

Re: 1963-1967 jack spring assembly

According to my 2010 1966 NCRS Technical Information Manual and Judging Guide regarding the jack retainer it reads "a cadmium or zinc finished single hook". So is the manual leading me astray? What will the judges at the London Regional be looking for?

[Jim D.]

Re: 1963-1967 jack spring assembly

1965 #14790 has a single hook, type 1 jack, and a handle with a hole and a rubber ring.

[David L.]

Re: 1963-1967 jack spring assembly

Jim,

Was your 1965 made in mid to late March 1965?

Dave

[Michael H.]

Re: 1963-1967 jack spring assembly

1965 #14790 has a single hook, type 1 jack, and a handle with a hole and a rubber ring.

I think the single hook continued into the 66 model year, even though the AIM's disagree.

[Jim D.]

Re: 1963-1967 jack spring assembly

Jim,

Was your 1965 made in mid to late March 1965?

Dave

Build date was 4-10-65

[David L.]

Re: 1963-1967 jack spring assembly

I think the single hook continued into the 66 model year, even though the AIM's disagree.

Michael,

You may be correct as most of my 30 year collection of 1963-1967 jack spring assemblies have the single hook, a 15:1 ratio as shown in my photo. I can see why the spring length was lengthened in 1969. Does anyone need a hook?

Dave

[Peter J.]

Re: 1963-1967 jack spring assembly

I wondered about this topic as I have pretty much unmolested late 66 (June -22nd, 66) and it has a single hook. I have aquired an original used double hook unit but don't think I will change it now.

[David L.]

Re: 1963-1967 jack spring assembly

I wondered about this topic as I have pretty much unmolested late 66 (June -22nd, 66) and it has a single hook. I have aquired an original used double hook unit but don't think I will change it now.

Peter,

When I bought my 1966 Corvette (Feb. 24, 1966) in 1979 it had the original jack and a jack handle with one hole but the jack spring assembly was missing. I'm sure when the theoretical change was made from the single to double hook they must have have a lot of single hook spring assemblies still in stock so they continued to use them until they were gone.

Dave