C3 Frame

[Dan Tewell]

What year frames would work on a 73 Corvette. I've heard that 69-73 would work, but I want to ask some people that would definitely know. It' an automatic. Can a 4 speed frame be made to work? I know that the automatic crossmember bolts in and the 4 sp is welded in.Thanks in advance.

[Joe Lucia (12484)]

Re: C3 Frame

Dan------

1969 to 1972 frames will interchange without modification. For 1973, slight modifications have to be made with respect to the body mounts, although I've heard of folks using the 73 frames as-is without significant problems. 1974 can also be used with slight modifications.

You can use an automatic frame with bolted-in crossmember for a 4 speed application. However, you can't use a 4 speed frame with welded-in crossmember for an automatic application. At least, you can't if you want to be able to remove and install the transmission with the body on the car.

[Dan Tewell]

Re: C3 Frame

Thanks, Joe. I was thinking that the front of a 73 frame might be different than the 72 because of the urethane bumper.

[Joe Lucia (12484)]

Re: C3 Frame

Dan------

For the most part, the 73 front bumper and the 74 front and rear bumper understructure was attached to a more-or-less similar front and rear frame horns. Crash bumpers were in their "infancy" then and, for these years, the design was simply an "add-on" to the existing frame design. In later years, this changed.

Beginning in 73, though, the change was made to the "rubber" body mounts from the aluminum pucks used for 68-72. So, the frame mounting points were revised to accomodate the new and thicker mounts.

[Dan Tewell]

Re: C3 Frame

Thanks Joe. So I guess thats how to make a 69-72 work on a 73. Just use the 73 style mounts. So, it's not possible to convert a 4 sp frame to an auto? Got to replace this 73 frame auto thats way too rusted to salvage. Some one did a do it yourself undercoating job on it and it just caused it to "power rust". I've found a 71 frame for around $1500 that looks good, but it's a 4 sp. Bummer.