Rear Transmission Support - engine install

So I finally had time on Labor Day to install the 521/C-6 combo into the 75 Sport. I definitely felt as if I was shoehorning it in there. With the headers it is an extremely tight fit. In fact, the driver side header touches the upper A-arm and the pass side will touch the brake line by the A-arm so I will have to modify the line.

The front end is all off at this time. Can't imagine doing it without everything cleared away.

The problem I am having is the rear transmission crossmember. I know several have complained of the same problem in the past - and I actually had trouble finding some of the better conversations on the topic we've had here over the years.

Predictably, I could not get the two studs of the rear trans mount over the crossmember. Even with the trans/engine as far back as I could go (say two inches forward of being on the frame) at max height I could not even think of clearing it.

What I ended up doing is getting the engine/trans in, and then placing the crossmember in. Currently it is just sitting there. I unbolted the mount from the transmission and played around with the mount/crossmember a bit. Those bolts going into the transmission are impossible to thread when the mount is in place, and there is no way to place the crossmember with the mount in place.

I think the crossmember might be slightly bent. My brother had taken the car 4x4'ing when he owned it 20+ years ago, and as such the frame had some bends in it as well as the crossmember. I could get a new crossmember (which I will endeavor to do), but even a slight bend maybe is 1/2 inch or something, not the 2+ inches I need to correct this issue.

Is there an alternative transmission mount available? Can I modify the one I have? Any other ideas?

I am so close to having this completely installed, and it is an important milestone for me and for the project.

What model C6 trans do you have? Long tailshaft(Lincoln/Thunderbird) or regular tailshaft? Pics if possible.  Make sure before you cut anything unnecessarily, that the engine is installed level, pretty easy to lay a 2 foot level across the left and right valve covers on a 460(may have to use identical sized spacers on each valve cover if a mid to high rise manifold is used), or even the intake manifold's carb base. Between the bolt clearance in the chassis and the bolt clearance in the motor mount there could be a combined clearance of about 1/8-1/4" of total movement up or down on each motor mount, totaled together that could be as much as 1/2" of allowable movement. I remember long ago when I installed my headers, I had to trim the rear corners of the upper control arms, about 3/8" or so diagonal cut with a cut-off wheel. Instead of having to move my brake lines I cut and formed heat shields from 16 ga sheet metal and tek (hex-headed self drilling screws)screwed them into place on the chassis to protect the lines and are removable. Good luck with your project, gotta love a stroked BBF. Todd

Scott, I have the C6 crossmember out of my '74 Ranchero. You can have it if you want, and I could bring it to Dawsonville. I have your '73 grill and surround packed if you still want them.

Looking more at that mount, it would appear that the side that mounts to the transmission may not fit a 1/2-13 bolt through it (which is what goes to the transmission). I am certain a machine shop could alter that for me though. Not a deal breaker.

I'll have to get underneath the car this week and look some more. I may order that mount if nobody has a better idea or alternative part.

aquartlow wrote: Scott,  Let me look through a few factory C6 mounts that I have, I seem to remember one of them having a similar style like the one in the pic you posted. I will try to find it tonight if possible and post a pic, hopefully I still have it. Todd

Max has got it correct. this is the way I've always installed my torino crossmember or any B car mount for that matter.

Ok, sounds like this is the plan. I need to make sure my existing crossmember is not bent upward or anything. It is a little tweaked where it did hit a rock (or something?), so I am not sure about the damage to it without having one side-by-side.

However, seems like the only way. I do know it will sit there, as I have placed the crossmember, the transmission and the mount there (without it being bolted in at the transmission side), and it rests there. The transmission seems a little high, but it fits. I did that just to roll it back and forth in the garage for now.

What we really need is a new crossmember made, an improved version. Something out 3/8 steel and much narrower so you can use the front holes and the straight mount in which you can get to the bolts that go into the transmission itself.

Sigh... Mine is bad in the wagon, so I guess I have this to look foward to.