Removable Tranny Crossmember

Does anyone have drawings for plates that could be welded to my differential crossmember to make the center section of it removeable? Of course, if someone has made some plates to convert their own car, and would be capable of easily making some for me, I'd be happy to pay for them.

I'd like to convert my 68 and the 70.

I do have a crossmember from an auto car and also it's brackets. So for at least one car, I have the option of just cutting out the manual crossmember and having someone weld in the brackets for the auto crossmember.

My 68 has a high ratio rear end (3000 rpm at 60 mph). I need to install a tremac 5 speed. Hence the desire for a removeable crossmember.

I have a bare frame for the 70, so converting to a removeable crossmember should be easy (well,...OK, OK I know easy things have a habit of being not so easy).

Your request is confusing. It sounds to me like you have a standard shift car and would like to make the welded transmission cross member removable, not the differential. This makes sense, since you mention you already have a removable automatic car cross member.Only the automatic transmission cars had a removable transmission cross member. You don't need to make the differential cross member removable.

That said, if my suspicion is correct, you need not replace the standard shift cross member with one from an automatic, but it is one way to do it. There are a few ways you can make your welded-in cross member removable. All methods that I am aware of require some welding and fabrication. If you have a bare frame, this is the best time to do it. Do some searching and you will find different ways it has been done. The location of your cut in the welded cross member is a personal choice. Most make the cut about 1/3 the way in on each side, with the middle 1/3 supporting the transmission.

When I did mine, I used two mating plates on each side, where the member was cut. The plates were pre-drilled and welded to the cut sections of member, with four bolts to secure each end. This is just one way among many to accomplish the same thing. If you remove the entire welded cross member and fit the automatic member, you will need to make tabs to mount the automatic member. It would seem easier to make the welded member removable, but that is my thought. I hope this helps.

Red said:

Your request is confusing. It sounds to me like you have a standard shift car and would like to make the welded transmission cross member removable, not the differential..

Click to expand...

Yes, that's correct. I want to make the transmission cross member removable. My comment about the differential crossmember was a brainless mistake. It's the transmission crossmember I'm concerned about.

Thanks

I didn't know you did the same thing Mike, ....so I will do my best to describe my '72 was a muncie car....

I had changed to auto tranny in '97, leaving it fixed, and so one time I got good and fed up with removing engine to get at the 700 tranny again, so I cut the cross member about 3-4" from each frame rail, had some angle iron on hand, cut 4 pieces of it, and in the rear of the removable section had them welded on large one on top, smaller on on bottom, this gave the rail total support, drilled holes going fore/aft for a grade 8 bolt and locknut....

now here is where it gets devious....I got sick of cutting the pipes also....

I cut the bottom of the pipe loops out at a WIDE angle like a olde tyme keyhole looking appearance....had a plate welded in on each side to put metal on the square box of the crossmember....took a plate about 3/4 inch or so from the top center of remaining loops going entire depth--fore/aft....

took another plate and went across the bottom of the vertical plate just mentioned....that makes like a bridge lattice to reinforce the weakened top loops.....

what this does is drop the pipes maybe a inch, so instead of the bottom of the old support loops, the pipes are open to the ground.....

it's still strong, and was done just about the time some aftermarket guys made commercial products but AFAIK, their stuff is for factory auto cars, dunno if it works for stick shift cars, I suspect not.....wind up pulling the body to be welding hell outta the frame rails I suspect....

I used to have a pix of it on the old computer that got wiped out last year....

:hissyfit:

This is a photo of my standard shift cross member that has been modified. If you look closely at the end, you will see the plate I used. There are two plates on each side, one welded to the stub still welded to the frame, and the other to the free member end seen. Four plate bolts hold each end to the frame. My cut was near the frame rail, but most choose to do this closer to the member center. Notice, I welded a section of pipe to move the exhaust port to the outside and free the exhaust to be dropped down. This had me choose my cut to the outside of the member. Good luck with whatever method you choose!

As an after thought, if you choose the method I have followed, you want to have the plates lean slightly closer toward the center. This will allow the removable section to easily drop down, or it will be locked from dropping and require being slid out the front or back.
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68/70Vette said:

Red said:

Your request is confusing. It sounds to me like you have a standard shift car and would like to make the welded transmission cross member removable, not the differential..

Click to expand...

Yes, that's correct. I want to make the transmission cross member removable. My comment about the differential crossmember was a brainless mistake. It's the transmission crossmember I'm concerned about.

Thanks

Click to expand...

PM Twin Turbo. I am "pretty" sure he has this on a cad drawing, or if not, an artiicle at least. I am sure Marck has just not seen this post.

I went with Bullshark's design (as shown in this thread) and had my local shop put it in for me since I don't weld. It's a pretty simple design. I have more write up on it in my build thread in my sig. So far, so good!