66 Drive Shaft

[Jim S.]

Today ,I decided to clean the Drive Shaft for my 66 SB .After hours of de-greasing, Lime Green paint started to appear along with the #"s 3742995.

According to the JG this is the sign for a "Big Block Only" Drive Shaft.

I was wondering if anyone else out there found this drive shaft on their SB 66 cars . Maybe a line shortage in late April to early May?

Also do these #s match up with that time frame?

Jim

[Joe L.]

Re: 66 Drive Shaft

Jim------

Actually, I don't think that there was a difference for big block drive shafts versus small block shafts. IF there was a difference, I would expect that the difference involved only shot-peening of the tube section which was the difference between small block and big block half shafts. But, I don't think so. Here's why:

The drive shafts used for Corvettes were supplied to PRODUCTION as an assembly which included yoke and u-joints. These assmblies were never available in SERVICE. The SERVICE part number for all 1963-1967 Corvette driveshafts was GM #3830618. This is the part number for the shaft "all-by-itself". As I say, this part number continued right through 1967 (and, 68-69, too, for manual transmission applications). Is it possible that GM used the big block drive shaft in SERVICE for all applications? Yes, it's possible. That's what they did for the half shafts. Once-upon-a-time, different half shafts were specified in SERVICE for big block and small block applications. However, the small block shafts were discontinued in favor of the big block shafts for all SERVICE. That's because the big block shaft was deemed adequate to SERVICE small blocks, so just one part number survived.

Could the same thing have happened for drive shafts? It could have, but it didn't. Keep in mind that the 3830618 was released for 1963. Big blocks didn't reside in Corvettes then. So, the 3830618 was, originally, a small block driveshaft. If Chevrolet had felt that a different, and presumably stronger, driveshaft was required for big block applications, then there's no way that they would have used a small block driveshaft for SERVICE. They might have superceded the 3830618 with a 1965-released big block driveshaft for all applications (as they did for the half shafts), but we know this did not happen. Could they have changed the specs for the 3830618? Yes, they could have, but if they did I would expect that this would have applied to both PRODUCTION and SERVICE after the specs were changed (after all, the 3830618 was the core unit for the PRODUCTION driveshaft assemblies).

So, I really don't think that there was a difference for big block driveshafts versus small block. Plus, for C3 era cars I KNOW there was no difference between driveshafts for small and big block applications.

By the way, where did this "3742995" number come from? Certainly, it was not stencilled on the driveshaft. It sounds more like a forging number for a driveshaft yoke end.

I would expect to see the number "3868727" stencilled on a 1966 PRODUCTION driveshaft.

[Jim S.]

Re: 66 Drive Shaft

Hey Joe,

I went back and looked at the JG again , and sure enough it is only the half shafts that were different. The Jg didn't start a new heading for "Half Shafts". It justs runs on from the "Driveshaft" section without a new title,and I went right along with it ! (I know... they are all driveshafts)

As per usual, your are correct about the #s ! (3742995) They are the forged #s underneath the Lime Green Paint on Driveshaft yoke end.

As to the stencilled 3868727, I can't see one now. I doubt it suvived the years ,or the rust coating , but I will clean softly and hope !

As Always your responces are informative and appreciated !

Thanks for the reply,

Jim