Xmember

[allons]

This may be the wrong site to post this but my '72 C10 LWB had a 6 cyl 3 spd which I am converting to a V8 5 spd. The 6 had a bell housing that was attached to a Xmember. My V8 bell housing doesn't have a way to mount to the Xmember. My question is: if I don't need the Xmember, can I just remove it? Thanks,

[steelhorse]

You can remove it. It is not needed for a trans with a rear cross member.

[allons]

Thanks, I was hoping I could remove all that metal without compromising strength. The Tremec has a location to mount the tail of the trans to a Xmember. Thanks again!

[SS Tim]

Site search is your friend as there are hundreds of posts about swapping engines and transmissions.

To answer your question all the 67-72 4x2 trucks with manual transmissions used rear engine mounts at the bell housing (four points) without a transmission crossmember.
Automatics used a transmission crossmember and mount (three points) without rear engine mounts.

If your planned swap transmission will not fit or adapt to the existing bell housing you can use a replacement housing without the rear engine mount provisions.

To do this you will need to remove the existing crossmember and replace it with a auto trans style crossmember that uses a rear transmission mount.

[allons]

Thanks SS, I usually look at searches but sometimes it sends me into the weeds. Your point is duly noted.

So, the V8 & 5 spd will essentially be a 3 point mount . . . 1 on each side of the engine and 1 near the rear of the trans?

[hugger6933]

That is correct. You will use a auto type rear crossmember and a rear type transmission mount for a say turbo 350 trans. It should be a perfect match.. Jim

[SS Tim]

That is it, three points. I would also suggest trying to source a factory automatic crossmember. THe crocodile style picks up both the upper and lower frame flanges adding a lot of torsion strength. A simple flat crossmember like a Camaro's won't provide the factory stiffness.

[allons]

Hugger & SS, I appreciate your comments and recommendations. In a short exchange of messages you have made it clear what needs to be done. Thanks!

[allons]

A question just came up . . . . . how far does the engine mount brackets have to move forward? and are there holes already in the frame for the relocated brackets?

[SS Tim]

If you look closely at the pictures I posted you will see three holes in the upper frame rail where the engine stand is located. Both of the pictured frames are V8 and show the stands in the forward pair of holes. The actual movement is about 3.8" and your frame should have the holes drilled. Bad news is the stands are not the same, There are at least three types: 6cyl, SBC and BBC. So you need to source a set of stands (and mounts) to do it right.

[allons]

Thanks again SS, I'm on the hunt for a couple of perches and an Xmember. Your help is appreciated. Jim

[Lattimer]

When i did my TREMEC I bought the whole kit from American Powertrain. They have a very nice aluminum crossmember they sell that worked perfect.

[SS Tim]

Originally Posted by Lattimer

When i did my TREMEC I bought the whole kit from American Powertrain. They have a very nice aluminum crossmember they sell that worked perfect.

It holds the trans up fine I'm sure, but as a structural member it isn't near the torsional strength of the factory crossmember.

[Lattimer]

Originally Posted by SS Tim

It holds the trans up fine I'm sure, but as a structural member it isn't near the torsional strength of the factory crossmember.

Correct, but the engine mounts take the torque. Any transmission with essentially a single point mount will not transmit a significant amount of torque out to the frame. 2 bolts 4" apart can't handle it.

A crossmember can be as strong as you want, but if the tranny twists off it-----doesn't help.

FWIW, American Powertrain warrants it and the trans to 600 ft-lbs. My engine put out just over 400 on the engine dyno, so I think I'm plenty safe.

[SS Tim]

True but the point is the factory rear engine mount or transmission crossmembers create a torsion box in the center frame.

Buy removing the factory rear engine crossmember and hanging a trans off the lower flange there is nothing really to stabilize the center frame rails in torsion. So any asymmetrical suspension loads are now being transmitted to the cab/cab mounts. This would be more pronounced on a LWB truck.