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There are a few different aftermarket kits that move the torque arm mount from the trans to the crossmember, as GM should have done it.
My own plans for eventually doing it entail a polygraphite mount, the interlocking one, and matching torque arm bushing in the bracket that holds it to the trans, on the 1-piece crossmember, then spot-weld small pieces of 1/8" mild steel between the mount bushing holder and the crossmember, then support the pan, unbolt the crossmember from the subframe rails and the polygraphite mount, weld the holder to the crossmember better, then cut the bolts on the trans tail. This can't be as pretty as the aftermarket alternatives, but it will cost less than $5. Just welding rod, scrap steel, and a little electricity.
That's no way to try to adjust the launch. Put it stock to ensure a safe pinion angle, then use multi-hole LCARBs and adjustable shocks to tweak the launch.
It doesn't work at all like a 4 link because the torque arm only acts in the vertical direction. Changing torque arm height has very little influence on instant center. Changing torque arm length has a strong influence.
The control arm angle has a strong influence to move instant center (IC) up and down. The torque arm length has strong influence to move IC fore and aft. The torque arm angle has a weak influence to move IC fore and aft.
GM chose a pretty good torque arm location. Drag cars with highly refined suspensions, purpose built for a single task of forward movement, operating on the fringe of traction might make adjustments of torque arm height. Why? Because it is the only practical way they can move IC fore/aft since torque arm length is set in stone once the suspension is built.
Car has Spohn adj.torque arm, SFC and adj.LCA with relocation brackets.
Since I have a 4L80E I made a new crossmember for the transmission mount and torque arm. Its very tight in that area and I'm not happy with it so I'm thinking of removing the end section of the inner subframe and replace it with square tubing more outward the car to get more room for the exhaust and a more ridgid crossmember for the torque arm. Will also shorten the torque arm around 1" to get more space.
Will place it like stock and make it adjustable somehow.
BMR and UMI have short torque arms. Downside is the cross bar has its own packaging problems because the exhaust is in the way. A cross bar with a dip around the exhaust is available but it results in lousy ground clearance.
I have a UMI short torque arm and my cross bar hits the road now and then. I'm not talking about bumbs, I'm talking about the flat road. It is ridiculous. I have to be very careful where I drive.
The transmission crossmember that you had (Spohn) is notorious and arguably the worst in terms of poor ground and exhaust clearance. I had a Spohn piece too and discovered how difficult it made exhaust routing. If you hadn't made your own piece I would say you'd be best off purchasing the new Hooker mount or one of the mounts that feature raised portions to go over the exhaust pipes. Although as a side note it's my personal belief that most if not all of the aftermarket suspension vendors do not contract an automotive engineer or mechanical or welding engineer to ensure their part is actually going to cause a benefit. It seems they either over build them or just wing it. Case in point spohn vs DSE outer subframe connectors. Is Spohn adequate and DSE is overbuilt or is DSE adequate and Spohn is a waste of time?
If you've made your own-- Post it up. We can't really offer suggestions without a good visual representation. What exactly did you using when making it? If you spend some time searching you can come across what seem to be decent crossmembers. I am still making mine and this is what I have so far:
It's a tubular piece 1" x 2" with a 0.120 wall. The brackets are 3/16" and welded to the inside of the front mount of the inner subframe connectors. This should hold a uniform load of 632 pounds. If the load were centered (which it is) it would be less. It seems like my design will work fine but then again, I'm not a mechanical engineer so I really don't know if it's good or not and if it's good what conditions it is good up to.
- One with TH700 and dual 3" pipes, solid as hell. There should be pictures here on thirdgen on it.
- The I hade to make a new one when I put in the 4L80E. Its much longer and there was no room so I had to use "flat" iron unless I would have ground clearence problems with dual 3"
This year im making one transmission crossmember and one for the torque arm. Will post pictures soon of what I'm planning. But I think I can use 35mm pipe 3mm thick for the torque arm crossmember.
11-29-2016, 02:35 PM
