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T56 crossmember modifications for a 69 C3

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Old 12-18-2011, 12:53 PM
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Default T56 crossmember modifications for a 69 C3

I've been searching all day and haven't found much.

I have a 69 vette with the non-removable trans crossmember.

I've seen pictures of some who just cut a section out and welded in a new plate but no measurements were given and I don't want to start cutting before I'm positive.
I plan on make side pipes work later on so I don't really care about clearance issues with the exhaust tunnels.

anyone with any suggestions would be grateful.

LS1/T56 showed up Friday night so I'm in for it now. Hoping this site along with corvetteforum will get me through the build.


Old 12-18-2011, 01:39 PM
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I'm just going to use Josh's (Custom Image) cross member, it's a direct bolt in. By the time it takes me to fab, cut, weld, get the proper angle,etc I could buy one and be done.
Old 12-18-2011, 03:16 PM
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Originally Posted by Big Block Stingray
I'm just going to use Josh's (Custom Image) cross member, it's a direct bolt in. By the time it takes me to fab, cut, weld, get the proper angle,etc I could buy one and be done.
I'm all for that. But given my crossmember isn't already removable I'm not sure how much fab work it'll take to get the pre-made one to bolt up.
Old 12-19-2011, 02:18 PM
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I would call Josh, and get his advice as he has done both bolted on (auto) and welded (4spd) stock crossmember conversions.

I called him an hour ago and ordered the crossmember for my '68.
Old 12-19-2011, 04:00 PM
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Not really a big deal to do this. I cut mine a few years ago and never looked back. I made my own brackets, not the prettiest ones but the work very well. I just cut on the outside of the tubes and welded on brackets for the middle part of the crossmember. I thru bolted them with a plate on the front. I dud make up some tubular spacers for the frame so it would not crush. I have had my TKO and now T56 in and out so many times I lost count. It is still working very well. If you are handy with a welder it will cost nothing if you can scrounge up some steel for brackets.

If the frame is out which I see it is this will be very easy to do.
Old 12-19-2011, 04:41 PM
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I've done the swap and conversion to removable crossmember to a '67, '69 and a '72.

I don't have time to do a write up but I could PM my phone number if you want to talk about it. It's not difficult.

Kerry P
Old 12-19-2011, 06:52 PM
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Originally Posted by Gordonm
Not really a big deal to do this. I cut mine a few years ago and never looked back. I made my own brackets, not the prettiest ones but the work very well. I just cut on the outside of the tubes and welded on brackets for the middle part of the crossmember. I thru bolted them with a plate on the front. I dud make up some tubular spacers for the frame so it would not crush. I have had my TKO and now T56 in and out so many times I lost count. It is still working very well. If you are handy with a welder it will cost nothing if you can scrounge up some steel for brackets.

If the frame is out which I see it is this will be very easy to do.
I do have a 120v welder but have never really welded anything of significance before. I filled in the stitch welds on the frame this summer and that was the first I've ever welded.

I'd rather not have to buy a $200+ crossmember that'll still require me to cut and modify my frame to make it fit when I could just cut a piece out and weld in the proper place.

I just don't know how deep I need to make it or the easiest way to go about it.
Old 12-19-2011, 08:18 PM
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The method in the photos is the simplest way of the three Vettes I’ve converted. This is a side exhaust car so no provisions for under car pipes were needed. After cutting the original crossmember out (including the exhaust pass troughs) I welded two heavy angles together to form a “U channel”. This was sized to fit snugly on the remaining original crossmember. I match drilled the new U channel to the original stubs of the factory crossmember (since a box section was replaced with an open U channel I increased the wall thickness of the U significantly). I also added spacer tubes inside the original box member so that it would not try to collapse when the bolts are tightened. Some trimming around the trans mount was required. The cars I’ve done were first generation engines with Viper T56s modified for use with GM. I don’t know if your mounts will line up or require an additional bracket. My transmission mounting holes were in line with the crossmember.

Kerry P.
Attached Thumbnails T56 crossmember modifications for a 69 C3-dscn4950.jpg   T56 crossmember modifications for a 69 C3-dscn4957.jpg   T56 crossmember modifications for a 69 C3-dscn4963.jpg  
Old 12-20-2011, 04:10 AM
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here is my setup. Basically a wide piece of angle iron cut some. This way I can lay the crossmember on the frame without bolting it in yet. The front is just a 1/4 inch piece of flat steel. One bolt one way the othe from the front. This is an old picture with a TKO but I still use the same crossmember just modified the mount.




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