Frame restoration/replacement question

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Mar 18, 2012 | 10:41 PM

CaseyJones

Thread Starter

Melting Slicks

Joined: Jul 2010

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From: McGrady NC

St. Jude Donor '15-'16

Frame restoration/replacement question

Now that I have my '80 in good running condition, I am considering buying a rolling chassis and rebuilding it to replace the well used one under my excellent fiberglass. That way, I can continue to enjoy my baby and then, when the time comes, simply (manner of speaking) move the body over to the fresh frame.

Now the tricky part. What frame, stock '80 or earlier, will work under my current car's body? I'm more interested in durability than esthetics. Would a '79 or earlier frame with its better rear differential section work? I don't want to modify my '80 body unless it is a minor change and absolutely necessary. I currently use an automatic and plan to keep things as they are.

Any information would be appreciated. Thanks!

Mar 19, 2012 | 10:45 AM

Red 69

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From: Space Coast Gator Territory

You might like to read the bottom portion of this document (see link).
http://www.71corvette.com/frames.html
Comparing the 78/79 frame to the 80 appears the body mounts are in the same location, so this is good. The main difference is the different carrier crossmember for the new for 1980 Dana 36/44. I t appears your 80 body would bolt up to an 78-79 frame with minimal modification. The major change was the differential, so you will likely need to also use the 79 drive shaft, in addition to the other IRS parts from the 79 donor car. If you are going drag racing, the iron diff will be way more durable.

Mar 19, 2012 | 11:45 AM

mapman

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From: Wichita KS

Before you get too far into this project, call your DMV and see if the VIN goes with the body OR the frame. I know in some states the FRAME is what determines the VIN.

What is the problem with the 1980 frame that requires replacement?

Last edited by mapman; Mar 19, 2012 at 11:48 AM.

Mar 19, 2012 | 11:55 AM

nate99

Race Director

Joined: Mar 2008

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From: coffee

Quote:

Originally Posted by mapman

Sounds to me like he wants to do a frame off resto while still having the car. A pretty cool idea if you have the space.

Would you be opposed to building up one of the aftermarket frames? They are probably a whole lot more expensive, but they sure look cool.

Mar 19, 2012 | 12:28 PM

Easy Mike

Team Owner

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From: Southbound

Cruise-In II Veteran

80-82 frames are unique because all the brackets and cross member are bolt on and the bat wing mounting for the rear. Other frames will fit, but you'd be doing much more work than you want to do.

There is absolutely nothing simple about putting your body on a different frame. Don't kid yourself. It's a big job.

Mar 19, 2012 | 12:36 PM

BarryK

Le Mans Master

Joined: Apr 2004

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From: Newark DE

Quote:

Originally Posted by mapman

most places it's the Body VIN. In fact, many states don't even know to look for a frame VIN.

A few years back we swapped out a frame on a fellow club member's '80 because the frame was massively cracked in multiple places.
Car owner lived in NJ and they never had a p[roblem with NJ DMV - all they checked and looked at was the body VIN and never even asked about any other places to check.

Mar 20, 2012 | 01:56 PM

Red 69

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From: Space Coast Gator Territory

Quote:

Originally Posted by BarryK

most places it's the Body VIN. In fact, many states don't even know to look for a frame VIN.

A few years back we swapped out a frame on a fellow club member's '80 because the frame was massively cracked in multiple places.
Car owner lived in NJ and they never had a p[roblem with NJ DMV - all they checked and looked at was the body VIN and never even asked about any other places to check.

This is true for the older cars, they go by the A-pillar vin tag only. The frame vin is located on the drivers side frame top behind the wheel. My 69 frame was rust compromised enough I didn't want to trust it for performance driving. After sandblasting, the frame numbers were not clearly visible and many people doing a frame off never knew they were there. An inspection station would not likely to be able to them without taking the body off. I swapped my 69 frame for a 73 with no problem. A 78/9 frame should be a plug and play for an 80, as long as an earlier C-3 IRS is used. In reality, if one wanted to go through the work, an 80 frame could be modified to accept the iron differential crossmember and parts, but then the car would be out of service during the process. Asking the DMV about this would likely lead to a confusing and vague answer IMO.

Last edited by Red 69; Mar 20, 2012 at 02:01 PM.

Mar 20, 2012 | 09:29 PM

L71Swede

Racer

Joined: Apr 2007

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From: Marshall MI

You can use your 1980 center section with the earlier style cast iron rear cover, which you'll encounter if you swap to an earlier frame. You'll need to heli-coil two of the already-drilled, but not threaded, holes in your 1980 pumpkin, then bolt a cast iron cover on the aluminum center section. I am running a 1981 center section in my '78, which is otherwise stock. Yokes and halfshafts from the 81 were used also. I did it for 3 reasons: 1. Had a low mileage 81 diff in a parts car, 2. had a shot 78 diff in the car, and 3-I wanted to see if it would work. For a highway driver, I like the numerically lower gear.