66 frames; w/ and w/o rear sway bar

[Gary B.]

Can anyone tell me if 66 frames for cars that came with a rear sway bar are different from 66 frames for cars that did not come with a rear sway bar? My 66 small block car did not have a rear sway bar, but I notice two small holes of each rear frame rail with internal weld nuts inside the frame. The holes are 2" and 4.5" rearward from the 2nd to last rear cross member. Are these the holes where the sway bar bracket would be mounted? I can't tell exactly what these holes are for since the entire rear suspension is removed from my car and I'm just guessing that these holes were related to the sway bar. However, I thought non-sway bar cars didn't have the weld nuts on the inside of the frame and my frame clearly has them. For that matter, I didn't think non-sway bar cars had the holes at all. Can anyone clarify this point for me?

Thanks,

Gary

[Steve Miller]

Re: 66 frames; w/ and w/o rear sway bar

Gary -

My 66 small block coupe frame also had the holes and weld nuts installed. I retrofitted a sway bar.

Steve

[Joe L.]

Re: 66 frames; w/ and w/o rear sway bar

Gary-----

For 1966, I think that all Corvette frames, whther used for big block or small block applications, had the weld nuts for the rear sway bar bushing retainers. Sometime later, and I don't know when it began, at least some of the frames for small blocks did not have the holes or the weld nuts. My 1969 small block frame did not have them, so I know that at least one car was built that way.

During the period that the frames were manufactured both with and without these weld-nuts, I think that the use of the versions without weld-nuts for small blocks was intermittent.

Quite frankly, it boggles my mind that GM specified the manufacture of frames with and without the holes and weld nuts. As far as I know, this was the only difference between the big block and small block frames. It would seem like having to keep track of 2 different sets of frames for the PRODUCTION line (i.e. auto with holes/nuts, auto without holes/nuts, manual with holes/nuts, and manual without holes/nuts) would have cost more than the savings produced by having some of the frames manufactured without the holes/nuts.

[Gary B.]

Thanks, Gentlemen. *NM*

[Gary B.]

Joe, a follow-up question

Joe,

I hadn't thought about the differences between cars with automatic vs. manual transmissions. Do you know how these frames differed for 66? Did the auto cars not have the brackets for the clutch cross shaft and did they not have the two off-center holes in the rear of the center crossmember for the shifter bracket?

Gary

[ronnie robertson # 36786]

66 July Power Glide

My July 66 powerglide car has the bracket for the clutch cross shaft. I don't know about the two off-center holes in the rear of the center crossmember for the shifter bracket because my car is in the paint shop. Will look, maybe next week!

[Joe L.]

Re: Joe, a follow-up question

Gary------

The primary difference between automatic and manual transmission frames which I was referring to related to the removable crossmember used for THM-equipped cars from 1968 to 1978. 1963-67 frames for automatic and manual transmission both used the same, welded-in crossmember.

As far as the clutch cross shaft bracket goes, I think that for 63-67, most, if not all, of the frames, whether automatic or manual trans, had the bracket.

As far as the crossmember holes for the shifter bracket mounting, the shifter mounting bracket began to be used in mid-1966, or so. I don't know if any early 1966 frame crossmembers had the 2 rear-side holes, or not. It's even possible that St. Louis had to add the holes for the first bracket-equipped cars until the frame change which included the holes reached the production line. After that time, though, I think that all remaining 66 and 67 Corvettes, whether manual transmission or automatic, had the holes. Keep in mind that these are just holes----no weld nuts were used for this installation as the bolts were self-tapping into the crossmember itself.

For 1968-78, I don't know if the removable crossmember for THM-equipped cars had the holes, or not. Beginning in 1979, though, when the removable crossmember began to be used for all Corvettes, the holes must have been present for manual transmission-equipped cars and, very likely, were present for both manual and auto trans cars. Once again, although the configuration of the bracket changed for 1968+, the rear mounting points still used 2 self tapping bolts with no weld-nuts.