Frame part #'s

[jeepergreg]

I recently bought a 63 roadster which had been wrecked in 72 and never put back together. It has a new frame with it which was purchased new in 75. The GM part numbers are Gr. 7003 part #3900200. I need to know what year this frame fits. I don't know which year body mount kits to buy. I have a part book whick goes up to 65 and it is not listed in this book.

 

[WayneC]

I can't find the part number in my 1976 parts book, but it does show frames for 1968 through 76 and it's not one of those. There is a 3900266 for a 63-66 tranny cross member, so it's likely a midyear frame, question is, which year?

Here are some clues:

On the 63 roadster frame, the body mount brackets just forward of the tranny x-member (center body bracket of the three on each side of the passenger compartment below the door sills) are shown in the shop manual as being 0.44 inches lower than the others, while the 64 shop manual supplement shows the center brackets as the same height as the others. I don't know if that's a misprint or not. I don't have measurements for 65-67 frames, but I think they probably match 64.

Also, on the 63, the 4 corner mount brackets for the passenger compartment are 0.32 inches higher in respect to the frame rails than are those on the later frame. See below for possible ways to tell the difference

On the later frame, there is a pronounced indentation atop the front crossmember to accomodate the larger balancer on the big-block engine, and there will be some cross-corner small braces (gussets) between the side rails and the crossmember that the rear wheel kickups are welded to. The indentation and the gussets mean a 65-67 frame.

One possible way for you to tell the difference is if you can measure the vertical distance up from the centerline of the trailing arm pivot bolt hole to the level of the top of the body mount close by... it would be 0.35 inches on the later frames and 0.67 inches on the 63 frame

I think the body mount cushions were about the same from 64 to 67 (some minor differences in 64), and I've been told they can be used on a 63 frame, they just raise the body slightly

If what you have is a 64-67 frame, you'd need to shim the center mounts of the passenger compartment sills by 0.44 inches to mate with the 63 body, assuming that mount really is lower as shown by my 64 shop manual (easily checked with a straightedge). Additionally, you'd need to shim the rearmost outboard side mounts by
0.25 inches.

Hope that helps.

 

[Tom Bryant]

Great info from Wayne. The problem with frame part numbers is that whenever there was a change to the engineering specs it got a new part number. Then It became the "service replacement". The part number for a '63 probably changed several times before it was discontinued. As far as GMPD is concerned a service replacement part just has to fit and function correctly. Not necessarily appear identicle to the original on a non appearance item.

Tom

 

[JohnZ]

3900200 shows in my August, 1973 P&A-30 as the frame for '63-'67.

 

[Tom Bryant]

3900200 shows in my August, 1973 P&A-30 as the frame for '63-'67.

You know, I have some early '70s parts books from my Chevy dealer days down in the "archives". Maybe I should do a basement search this weekend. Thay surely have numbers that my '82 book doesn't have. I also have a '60 parts manual if anybody is ever looking for original early numbers.

Tom

 

[vette]

frame numbers

if the frame was bought new in 75 you do have a service part # . which means it is a 67 frame but all mid year frames are the same more or less.they changed brackets added gussets, front crossmember is a little diff. to make room the the big block. if you are going to build a points car that frame wont fly. if your going to build a nice driver your in. as you know you cant buy mid year frames new and good used is an arm and a leg. just make sure your frame rails in the rear behind the wheels has a small curve in it . 68 and up the rails are level in the rear. i would use the later body mounts they did improve as years went on.gm did the same with 85 to 96 C4 hoods you can put a 96 hood on a 85 car but cant put an 85 hood on the 96 car. when they changed to the LT1 in 92 they had to make room for the ac. and alt. thats how GM dose things. good luck i wish i had a brand new mid year frame lying around.