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January 20, 2010 - The transmission crossmember is finished.
Finally! It's upside down in the picture, in the car it steps up to reach the stock LS1 transmission mount. The bits on the end bolt in to captive nuts installed on the frame rails. Of course, I didn't have that set up ahead of time so I first had to weld the nuts on to a piece of 1x2" strap, cut two large 0.875" holes in each frame rail and then weld the strap on to the rails. The holes in the strap and the bracket are perfectly matched to the bolt size so there's no slop at all, which made positioning very important. I put the bolts in shear instead of tension for the simple reason that if they start to back off, my transmission won't start to sag downwards and eventually fall down.
The stud on the rubber bushing on the transmission is an inch long, which isn't long enough to protrude all the way through my mount. Thus the large hole in the middle, which is where the nut for the stud goes through along with a socket to tighten it up. Works like a charm, although I really need to deburr that hole to make it look better in pictures like this.
The raised middle section didn't end up being raised quite enough - the original measurements told me 0.75", and it looks as if 1.25" would have been more accurate after I decided the tail of the transmission needed to be slightly higher. Oh well, it's a good solid fit and it works well. Due to the close tolerances on the holes, it's actually a bit tough to install as the bolts won't thread into the holes unless the mount is perfectly positioned, but I'm willing to accept that particular tradeoff for a precise fit.
tags: transmission