How to identify a frame
Thread Starter
Instructor
Joined: Apr 2015
Posts: 131
Likes: 26
From: Fort Valley Georgia
How to identify a frame
I have considered picking up another frame to start restoring and when the time is right just swap everything over.I have a '76 coupe with an automatic. I mention my transmission because I have noticed that it has come up a lot with people selling frames. I have never known of a car that the frame is made different because of it being a manual or automatic. Convertibles often have different frames as do big block cars. You get what I'm asking. Also I know there is a number stamped on the frames. But I don't know where I would go decipher it.
Racer
Joined: Nov 2014
Posts: 463
Likes: 129
I have considered picking up another frame to start restoring and when the time is right just swap everything over.I have a '76 coupe with an automatic. I mention my transmission because I have noticed that it has come up a lot with people selling frames. I have never known of a car that the frame is made different because of it being a manual or automatic. Convertibles often have different frames as do big block cars. You get what I'm asking. Also I know there is a number stamped on the frames. But I don't know where I would go decipher it.
C3 Corvettes do have different frames for cars with manual and automatic transmissions. This why it is always mentioned by the people selling frames. The difference is in the transmission cross member. On manual transmission cars the cross member is welded in. On auto transmission cars it is bolted on. The bolted cross member aids in removal/servicing of the larger auto transmission.
Coupes and convertibles all use the same frame. Convertibles do have more body mounting points then coupes but they were welded on at the assembly plant, as received from the frame manufacturer they were the same. You can easily weld on or remove the body mounting points as needed when replacing a frame.
Small and big block use the same frame.
The number stamped on the frame is the partial vin number of the car. It was also stamped on the engine and transmission. It was to help identify the major parts of the car if it was stolen. It doesn't help identify options or anything like that.
John
Team Owner
Joined: Sep 2006
Posts: 31,230
Likes: 4,324
From: Westminster Maryland
Hi John,
"Convertibles do have more body mounting points then coupes but they were welded on at the assembly plant, as received from the frame manufacturer they were the same."
I wasn't aware that convertibles had additional body mounts compared to coupes and that their frames were modified from coupe frames.
Where were the added mounts?
Regards,
Alan
"Convertibles do have more body mounting points then coupes but they were welded on at the assembly plant, as received from the frame manufacturer they were the same."
I wasn't aware that convertibles had additional body mounts compared to coupes and that their frames were modified from coupe frames.
Where were the added mounts?
Regards,
Alan
Last edited by Alan 71; Jun 2, 2015 at 07:29 AM.
Drifting
Joined: Jan 2012
Posts: 1,908
Likes: 129
From: Fredericksburg Virginia
I agree.
I disagree.
Additionally, you can use a manual frame on an automatic and vice-versa. The difference is the removable trans crossmember on the automatic and the addition of the z-bar tab on the manual. You can certainly leave or remove the z-bar tab easily enough if using a manual frame on an auto car, but the removable crossmember is desireable for either transmission.
Us manual trans folks wouldn't mind being able to remove/service the transmission/clutch without pulling the engine. I understand that it is possible, but extremely tricky. Modification to the trans crossmember to make a chunk of it removable is on the modification list for the 1976 frame I have hanging in my garage which I'm modifying for use in my 1970.
As far as year range, you can use a 1975 frame up and including a 1979 frame with zero modifications. 1974 and before had a different bumper assembly rearward of the rear crossmember. And they completely changed the rear crossmember assembly in 1980 and later. You can modify a pre-1975 frame for your use easily enough, but those earlier frames in good condition are generally more costly than a frame from your 'generation' of C3.
Differences between frames 1963 to 1982
Additionally, you can use a manual frame on an automatic and vice-versa. The difference is the removable trans crossmember on the automatic and the addition of the z-bar tab on the manual. You can certainly leave or remove the z-bar tab easily enough if using a manual frame on an auto car, but the removable crossmember is desireable for either transmission.
Us manual trans folks wouldn't mind being able to remove/service the transmission/clutch without pulling the engine. I understand that it is possible, but extremely tricky. Modification to the trans crossmember to make a chunk of it removable is on the modification list for the 1976 frame I have hanging in my garage which I'm modifying for use in my 1970.
As far as year range, you can use a 1975 frame up and including a 1979 frame with zero modifications. 1974 and before had a different bumper assembly rearward of the rear crossmember. And they completely changed the rear crossmember assembly in 1980 and later. You can modify a pre-1975 frame for your use easily enough, but those earlier frames in good condition are generally more costly than a frame from your 'generation' of C3.
Differences between frames 1963 to 1982
Last edited by keithinspace; Jun 2, 2015 at 10:54 AM.
Racer
Joined: Nov 2014
Posts: 463
Likes: 129
Hi John,
"Convertibles do have more body mounting points then coupes but they were welded on at the assembly plant, as received from the frame manufacturer they were the same."
I wasn't aware that convertibles had additional body mounts compared to coupes and that their frames were modified from coupe frames.
Where were the added mounts?
Regards,
Alan
"Convertibles do have more body mounting points then coupes but they were welded on at the assembly plant, as received from the frame manufacturer they were the same."
I wasn't aware that convertibles had additional body mounts compared to coupes and that their frames were modified from coupe frames.
Where were the added mounts?
Regards,
Alan
For C2's the number 2 body mount was not used on coupes, I had always assumed that carried over for C3's as well. It appears that was a wrong assumption.
John
Racer
Joined: Nov 2014
Posts: 463
Likes: 129
For most Corvettes, yes. A partial vin stamp would look something like this: 14S404516.
The number is front of the S is the model year. 4 = 1974
During the early C2 era the model year was not always included in the partial vin.
John
Thread Starter
Instructor
Joined: Apr 2015
Posts: 131
Likes: 26
From: Fort Valley Georgia
Thank you. All of this has been great information. When I mentioned convertibles and big block cars as an example i wasn't really speaking about corvettes but of cars in general. I have played with a lot of different cars and the corvette has been the first one i have come across where the manuals and automatics frame was built differently. But a lot of the vehicles I've owned have been trucks. Lol.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Top 10 Corvette Engines RANKED by Peak Torque (70+ Years of Muscle!)
Joe Kucinski
Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!
Verdad Gallardo
Top 10 Corvettes Coming to Mecum Indy 2026!
Brett Foote