I've got a bare solid '70 coupe chassis I'm building for my '69 to make it a cornering car.

How do I make the trans crossmember bolt up if I've got my holes covered up after it's boxed? I would just weld a nut on the inside, but I don't know which holes I will be using when I put the 4L60-E in it graemlins/clonk.gif

Also, if there's any places where these frames are typically weak and/or flex a lot, I'd like to beef it up a bit. I'm going to re-do all of the factory welds on the whole frame. I'll also gusset the lower front A-arm's rear-mount. Any other areas to look at?

The usual braces to tie the rear control arm mounts together. Good chance you've already got 'em.

Yeah, I have the rear braces. :cool:

Dont know if this info will help, but I have a 4L80E in mine I had to use the hole farthest back and modifiy the crossmember. Mine is also a convertible.
If you do weld nuts to the frame before you box it I would put nuts in all the holes. You might want to change the trans in the future.

can someone describe this brace for me. does it make a difference?

Its a brace that gets bolted where the rear control arm are. From upper to the lower. Triangulates (sp??) that section of the frame.
Some cars came stock with them. Aftermarket sells them also.

where can i buy one? or find a picture of it?

pretty sure the f41 option for the rear upper and lower control arms are the braces you are talking about I've got a few sets for 68-72 can't sell them here though so e-mail me and I will fill you in better if you can't find them

hey derek, i don't think the other guy's are quite following you. what you need is a elcamino or convertable crossmember and make brackets to bolt to and weld them to your frame reinforcements. how did you construct your reinforcements? tom

Why not just leave a small gap between the boxes so you can put a few nuts on? And access it with a wrench?

Chris.

tlowe I did not construct them they are the stock brackets that bolt to the front of the upper and lower control arms for the rear
derek you can cut the boxed part out of an elky frame and modify it to fit the frame
it will be too long but you just cut off the back about 4" and weld it right on your frame some slight modifying at the rear not to major though actually just cut the rear off romve amount needed from in front of the cut then weld the rear part back on
chances of finding a convertable frame are not so good and very expensive
don'tforget to get the crossmember from the elky you will need that too

If you box the frame how are you going to get the crossmember in? It sits on top of the lower channel of the frame :confused:

just cut acess holes in youe new boxed section so you can get to the bolts to bolt your crossmember in. the rear braces pthers are talking about look like this"
http://home.comcast.net/~petelohr/einstyn1/rear-c-arms-done.jpg
http://home.comcast.net/~petelohr/einstyn1/einstyn-08.htm

Derek,

You looking for something like this?
http://www.buffnet.net/~airrj/images/MyChevelle/Frame/Transmission-Mount-1.jpg

That is the solution that I came up with. You can see a few more photos here. (http://www.buffnet.net/~airrj/Frame%20modifications.html)

After I was finished with the boxing project I can't say that I would do it again the same way. The rigidity that I gained is not substantial, and the trans. mount was a real pain. The crossmember is held in by (4) 3/8" bolts with Nutserts installed into the frame.

I helped a friend of mine box his frame this fall and he had a much better idea. Instead of closing off the the frame into a square channel, we welded in a web of steel from the top outer edge of the frame to the inner lower corner of the frame. This allow the use of the stock crossmember still.

http://www.chevelles.com/showroom/airrj/Image2.jpg


http://www.chevelles.com/showroom/airrj/Image1.jpg

RJ, thanks for the idea!

That looks like one of the easiest ways to do it. My other idea I'm tossing around is to just box the first 8" or so where the side rails mate to the front section. I'd have to leave it open just enough to get the crossmember in and out.

I had some other ideas, but that looks like it will work the best.

I also considered "trussing" the frame with 1" strips at opposing 45* angles, but I'd still have to have an opening big enough to get the crossmember in and out.

Derek,

Why not just weld an additional bracket in the location as needed? Maybe using the El Camino/Convert crossmember.

I had an old El Camino racecar that someone swapped a TH400 into, and the stock crossmember sat on some angle iron pieces welded to the frame (and behind the stock mount location)... Then you can place them and drill holes as needed... You could even gusset those if needed...

RJ's new idea seems nice, but would that additional bracing piece be uniform size the whole way down the frame rail, or not? It would also be a little heavier too. Seems like a simple box with add-on brackets and an ElCo crossmember would be a little easier to fab up...