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LS swap trans crossmember

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Old Mar 21, 2010 | 08:01 PM
  #1  
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From: Hou. TX
Car: 86 TA, 91 B4C
Engine: 5.3, 4.8
Transmission: 4L80 4000, T56
Axle/Gears: 4.30 M12, 23.42 10 bolt
LS swap trans crossmember

What should i di, the Spohn SUCKs and my exhaust scrapes everywhere, the torque arm is set up to mount to the trans crossmember, so any ideas? Mount it to the frame with some custom fabbing and a custom trans crossmember? Only idea i have.
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Old Mar 21, 2010 | 08:31 PM
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Car: 91 Trans Am
Re: LS swap trans crossmember

Cut and weld humps in the crossmember for more clearance
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Old Mar 22, 2010 | 07:17 AM
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From: Hou. TX
Car: 86 TA, 91 B4C
Engine: 5.3, 4.8
Transmission: 4L80 4000, T56
Axle/Gears: 4.30 M12, 23.42 10 bolt
Re: LS swap trans crossmember

Yea, but there is still the problem of where the TQ arm attaches right where you need a hump on the driver side.
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Old Mar 22, 2010 | 08:29 AM
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Car: 91 Trans Am
Re: LS swap trans crossmember

You shouldnt need to tuck it that high

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Mine is raised roughly 1.5" and Ive never had a ground clearance problem. My LM1 resonator is the lowest point in the exhaust and its only touched in severe bumps
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Old Mar 22, 2010 | 10:42 AM
  #5  
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From: Littleton, CO USA
Car: 82 Berlinetta/57 Bel Air
Engine: L92/LQ4 (both w/4" stroke)
Transmission: 4L80E/4L80E
Axle/Gears: 12B-3.73/9"-3.89
His torque arm mounts to the crossmember, right where you need the hump.

So far, it doesn't appear that both issues of humps for exhaust clearance and mounting the torque arm to the crossmember have been addressed. An alternative is to use a torque arm that mounts to its own crossmember, but if you already have a crossmember-mounted Spohn torque arm, you're hosed without major modifications.
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Old Mar 22, 2010 | 11:59 AM
  #6  
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From: Warrenton, VA
Car: 1987 Camaro IROC-Z
Engine: LS1
Transmission: LS1 T56
Axle/Gears: Richmond 3.73
Re: LS swap trans crossmember

you only have 1 bolt on each side of the crossmember?
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Old Mar 22, 2010 | 01:10 PM
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Car: 91 Trans Am
Re: LS swap trans crossmember

I do, didnt see a need for two. A dab of blue locktite on the bolts and it wont be coming back out short of a breaker bar. I hung my weight from the crossmember and it didnt budge, so strength isnt an issue

Certain reason I need all 4?
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Old Mar 22, 2010 | 01:16 PM
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From: Hou. TX
Car: 86 TA, 91 B4C
Engine: 5.3, 4.8
Transmission: 4L80 4000, T56
Axle/Gears: 4.30 M12, 23.42 10 bolt
Re: LS swap trans crossmember

I only see a need for 4 if you are like me and want to beat it to death at the drag strip and EVERY time you drive it. I hacked a stock trans crossmember and it holds fine so i am sure that piece does very well.

I will just have to see what i can do to mod the spohn piece, i have cut it a bit, but i am sure i can come up with something, just the damn powder coating that gets in the way.
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Old Mar 22, 2010 | 01:20 PM
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From: Littleton, CO USA
Car: 82 Berlinetta/57 Bel Air
Engine: L92/LQ4 (both w/4" stroke)
Transmission: 4L80E/4L80E
Axle/Gears: 12B-3.73/9"-3.89
That frame rail material is pretty thin. In 1999 when I did the original V6 to V8 swap, I had to drill the back two bolt holes in my '82 (short tranny/longer crossmember mounted farther forward than the later years). I put a flat washer under each nut. In 2005 when I pulled engine/tranny for the 350 upgrade, the nuts had bent the washers and had distorted the actual frame rail.

I had to drill the same holes for my current LS1/T56 project, this time I put a piece of strap steel inside the frame rail and put the nuts on top of it. Much better support.

I'd suggest using all 4 bolts.
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