i have been looking at a frame for a 74 , what are the differences ? just the bracket for the shock on rear frame horn and can it be easily removed to be fitted to 69-72 without being detected Thanks in advance
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Re: 74 frame vs 69
kelly----
1969 to 1974 Corvette frames are, basically, interchangeable. Most everything that makes the various model years in this range different is bolted to the frame.In Appreciation of John Hinckley -
Re: 74 frame vs 69
Not really Joe, the 74 frame especially in the rear is much different and the differences are not bolt on. The whole rear from above the wheel back will be very different.Comment
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Re: 74 frame vs 69
Wayne------
The 1974 PRODUCTION and SERVICE frames, GM #339719 (manual transmission), and GM #339720 (auto trans with removable crossmember) became the SERVICE frames for all 1969-73 Corvettes. So, there's no doubt that the 1974 frames are rearward-compatible (with all 1969-73 applications). Of course, that does not necessarily mean that that earlier frames are compatible with 1974, but that wasn't an issue for this question. However, I believe that the 69-73 frames are compatible with 1974.
1975 (and, later) frames are NOT compatible with earlier applications, though.In Appreciation of John HinckleyComment
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Re: 74 frame vs 69
can you explain the difference , in the rear section , will or can it be detected under a 69 - 73 , thanks for the continued assistance .Comment
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Re: 74 frame vs 69
kelly------
I do not know what the differences are. Certainly, there are some differences or there would not have been a part number change. Actually, the frame part numbers changed almost every year from 1969 to 1974, but, in each case, the most current frames became the SERVICE frames back to 1969. So, the frames should be compatible. However, that does not mean that every facet of the frames from year-to-year is identical. Like I mentioned, if that was how it was, there wouldn't have been part number changes.
My original understanding of your question was that you were asking if a 1974 frame would work for a 1969. My opinion is that it will. The frame part numbers for 1974 Corvettes as used in PRODUCTION and as also available once-upon-a-time in SERVICE were GM #339719 (manual trans) and 339720 (auto trans). If, in 1974, you had purchased a frame from GM to replace the one on your 1969 Corvette, you would have been sold a GM #339719 or 339720.
Just how the 1969 frames differed from the 1974, I do not know. My expectation is that they did not differ in major ways because, if they had, they would not have been compatible.In Appreciation of John HinckleyComment
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Re: 74 frame vs 69
The frames are a little closer than I remembered. I dont think you will have much trouble with it. These things are more bolt on than i thought.
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Re: 74 frame vs 69
Didn't the 1974s have rubber body mounts? I think they did. As such the body mounting brackets on the frame will be in a different position than those on the 1969. I think you will be OK id you use the rubber mounts from 1974, but I don't know for sure. Someone else will likely know more about this than I do.TerryComment
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Re: 74 frame vs 69
Terry
Yes 74's and 73's had the rubber mounts but the location was the same as a 72 body. I have a 72 body on my metal solid dolly now and it was built for a 73. I think that the problem is the rubber mounts are thicker than the solid pucks used up till 72 so a 69 body on a 74 frame would set lower if you used the pucks. I have a 71 and a 74 frame so I will do some checking. This picture is when a 73 was on the dolly.
Lyle
Lyle
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Re: 74 frame vs 69
73 rubber mounts were a common upgrade for earlier cars. I put the 73 rubber mounts on my 69 and the body sat about 3/4" higher.Comment
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Re: 74 frame vs 69
I measured a 71 and a 74 frame and the #2 and #3 body mounts were the same heigth above the frame rail. The 72 pucks were 3/8" thick and the rubber mounts are 1" thick on a new mount. If the bodies were not changed 73 and up set just a little higher above the frame depending how much the rubber compressed.
LyleLyle
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Re: 74 frame vs 69
I know Joe is right in his comments. On occasion we have seen an early C3 with rubber mounts and the body sits higher -- enough that it is obvious -- in judging. I remember when it was common to add the rubber mounts to early C3s (I guess that really dates me ), and the report at the time was that the later frames had the body mounts lower to compensate for the thicker rubber mounts. This was pre-Internet, so those reports were the old fashioned kind -- ink on paper. Of course that makes them no more reliable. For all I know I am repeating a falsehood, but I do know what Joe said is right.TerryComment
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Re: 74 frame vs 69
Terry
I agree Joe is right. The difference that I measured between the metal puck and the rubber mount was about 3/4 inch in thickness the same as Joe said the body went up. I thought the mounts would be different also but having a 74 and 71 frame both with no body on them I found that they are the same 3/4 inch high at #2 and #3 body mount above the frame on both the 71 and 74 frame.
LyleLyle
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Re: 74 frame vs 69
Since you have both frames, you have the real information -- which proves that misinformation existed before the Internet.TerryComment
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