I had a high spec 700R4 built for the Camaro and while for all intents and purposes it has been performing perfectly it was unfortunately installed in the wrong case. The large letter "V" cast into the side of the bellhousing as well as the slightly shorter output shaft indicates that it's from a Corvette. This means that the rear transmission mount is located in the extension housing rather than the case itself.
As a temporary measure, I've cobbled together an adapter which uses two of the extension bolts as means to attach the poly mount to the stock crossmember. This is until I get around to installing the Hooker swap crossmember (and build a new exhaust).
My question to those interested in replying is how durable do you think this modification is? The torque arm is still attached to the extension housing so the bolts still transfer that force in the conventional route. Does the additional load of keeping the transmission in place impart to much force to those bolts and the case?
Keep in mind, I haven't raced the car in this configuration. About the most this part is stressed is during up shifts when the tires chirp.
Thanks in advance for any insights.

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Angle iron cut to fit around extension housing (before poly transmission mount fitted)
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Adapter bolted to case using 2 extension housing bolts
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Installed using the OEM crossmember
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I love ideas such as this. So smart, yet so simple AND EFFECTIVE.

So you are spreading the load/shock over 4 bolts instead of 2. Good idea. Not only that, but the 2 sets of bolts are in different planes. I seriously doubt if that will break.
I think I will copy that. IIRC, I had to put a 1/4" plate spacer between the poly mount and transmission anyways (for some clearance reason), so fabricating one of your mount strengtheners will solve both problems.

What size angle iron did you use?

 

I see what you're thinking. Unfortunately, the angle and mount are connected with only 2 bolts. The Corvette case being what it, there are no provisions for the rear transmission mount in the traditional 3rd gen location. The pictures below will illustrate what I'm referring to.
Should you want to copy it and produce what you've described, I used 2" x 3" x 3/16" angle. The radius was cut using a 4" hole saw.

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Traditional 3rd gen 700R4 case with integral holes for rear mount.
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Corvette case with a 3rd gen extension housing attached. Notice the absence of mounting holes.
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This is an extension housing from a Caprice 700R4. Using that for the rear transmission support means a new crossmember. The overall bell housing to rear mount distance matches that of a TH400. Hooker makes a crossmember designed for the application.
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Hooker crossmember.

 

You're right - no holes. Still a great idea and I will use it on mine. Thanks.
The more I look at your solution, the more I freakin' love it.

 

I remember your prior thread. Nice implementation.

The torque arm adds some up and down load on the tailhousing and mount.

If you're not going to beat on it much, run it, and inspect it on oil change time.

 

That's the plan.
The OEM design still placed the torque arm forces directly through the extension housing bolts. This is no different in that regard. My concern is the additional strain on the two bottom bolt holes that now take the entire load that were normally directed through the rear trans mount on the trans case itself. While the combined forces aren't in the same direction, there is obviously a greater load imparted there. A failure would probably mean a new case as I expect the threaded holes (in the case) would give way before the bolts.
So, yes. Take it easy. No slicks...