Structural integrity, torsion bar cross member need some opinions.

[DartorDemon]

I'm trying to get as many opinions as possible before i go through with this. My car is a mopar and is an A-body making anything tranny related(unless oem) a complete nightmare. Mainly because of the torsion bars. In my tranny tunnel there is this:

https://static1.pt-content.com/images/noimg.gif

That center loop gets in the way for every non-oem transmission. So then i found this online, its from the Gforce designs pro touring demon:
https://static1.pt-content.com/images/noimg.gif

The went away from the torsion bar suspension, gutted the center piece and added sub-frame connectors that go front to rear.

So this at first made me wonder if this alone would support that crossmember well enough to run T-bar suspension. And someone gave me another idea to strengthen the whole it some more by adding a cross-bar on the sub-frame connectors.(see attached paint drawing)

There would still be the lower bolt on piece to the T-bar crossmember and it would have the sub-frame connectors + cross bar to keep it from flexing.

So the question is: would that be strong enough?

[Motorcitydak]

Well, the best bet would be to do what those guys did and then put in a removable brace under the trans. Give it 2 bolts on each side of the tunnel and you should be good.

Think of if like this. You torsion bars can only transfer a twisting motion from one location to another. In this case, from the LCA to that crossmember. If they are both twisting the same amount and that crossmember was in 1 OEM piece but not connected to anything else what so ever, the crossmember would stay in the same place. The torsion bars are trying to twist towards the inside, pulling the trans tunnel area downward. If the crossmember was weak enough, it would allow that to happen. From the factory, it is strong enough to resist that.

Now, if you cut out the middle you have 2 2 foot long or so pieces that are completely separate from each other trying to twist on their own. They are welded to the rockers. That will be their pivot point. They will each twist down the inside ends of that crossmember. That will pull the floor pans downward which is not something they were designed for. They will eventually fail, the 2 pieces of crossmember will tear away from the floor and hit the pavement.

If you used frame connectors, and then a crossmember further back this will help but is far from ideal. The loads have to be transferred from the torsion bar crossmember, thru the connectors, then to your crossmember. Those connectors are good for tie-ing the front and rear together because the load is going in a straight line from rear to front. What you are now asking them to do is resist twisting load also. A 3 sided connector is not good at that. I could twist mine with very little force when they were not mounted.

If you are worried about room under the trans or clearance with the exhaust, I would suggest either oval exhaust tubing in this area or a short but wide crossmember. What I am thinking is a crossmember piece that is made sort of like corrugated cardboard. Maybe 3/4 plate for the sides and 2 inches or more wide. Use the 3/4 for the vertical pieces, 2 for the sides and another 2 or 3 pieces welded inside the piece. Weld them all to one flat piece that will be either your top or bottom then use more 3/4 to fill in the other side, a cross section would look something like this [III]. It would resist this load very well

[DartorDemon]

Obviously my picture is rough/simplistic, but the overall idea would be to get that cross bar as close to the torsion bar cross member as possible.

Also, those two pieces would technically not be completely separated. There is still the lower piece that bolts between the crossmember:
http://www.gforcedesignconcepts.com/albums/DEMON/IMG_6056.jpg

(but mine would likely be an oem modified piece.

[High Plains Mopars]

Agree with MCD, that crossmember is a major structural component for torsion bar mounting. Compromising its integrity could lead to catastrophic mount failure. It is important enough that I have seen others fabricate it in alternate dimensions to allow different transmission configuration, but never eliminate it. Even if it intrudes in to the passenger compartment, as it often did on competition cars back in the day, they never eliminated nor bypassed it for something else.

GForce eliminated the torsion bars and went coil overs. Therefore their mount only needed to function as floor support. It no longer had the loading forces a torsion bar is imparting. They can get away with that because of hte new suspension loads.

[MrQuick]

You can do what DSE does and creates a crossmember that is partialy in the drivers compartment with a shift hole surround.

[High Plains Mopars]

Notice how the factory reinforced the t-bar cross member in the factory oval track kit cars. That is WAY beefy and I'd say it is taking a fair amount of loading.

https://static1.pt-content.com/images/pt/2012/10/KitCarforPhill008-1.jpg

not my photo, I borrowed it from BHA43 on moparts.