bonus

Put simply, the transmission mount was a bit more complicated to build. It had a third controlling dimension and a third fixed point as compared to the engine mount design. The engine mounts only dealt with height + angle and forward + aft weld distance, requiring 2 connector plates cut to size and welded in parallel between the 2 mounting plates. Because of the drop in vertical position and distance forward to aft between the mounting plates, and the fact you have 2 car side mount points attaching to 1 transmission side mount point, you needed to precisely attach 2 connectors in series to each other on each side of the transmission.

I cut and test fitted cardboard pieces similar to that of the engine mounts for the car side plates. After this I dimensioned and cut them out of the same 1/4" thick plate. Once cut, I installed the car side plates and marked where the welds should be for the drop plates. The car side plates are not parallel with the car or transmission. The drop plates needed to be in the right forward/aft position and angle of rotation as compared to the angle of the car side plate to the car so that when the assembly was installed, the connector drop plate would sit perpendicular to the cradle tube. Once marked, I had Tony weld it.

As with all fabrication, trim as required.

Once I installed the car side plate and drop plate assemblies on either side of the transmission, I was able to measure the install location for the cradle. The issue I ran into was that the transmission plate was drilled and welded to the tube to face a certain direction. The drop connector plates on the car side portions were welded forward/aft to accommodate this direction. The connector plates are not equally spaced from the center of the transmission plate due to differences in they're position relative to the car. this would become very important later on.

In the meantime, I had to cut the transmission isolators level so that they would both support the transmission equally. This is a pain and it would have been easier if they were exact thickness out of the mold. The mounting surfaces would have been more level without cutting to size and due to the stackup of tolerances, the "center" nut/washer assembly that's built into the isolators was almost exposed on one side. Don't ask me how I know this. That, and it's just a messy process. It was important to be done first though, in order to accurately measure the length of the cradle tubes where it would actually sit once installed.

When I put the isolators in for a test fit of the cradle to mark the cuts of each side, I was unable to mark it facing the right direction and did so with it in backwards. This resulted in the tube lengths on either side being cut at the wrong (opposite) lengths because it was all based on distance from the center and it wasn't symmetric. I was able to trim the long side to match, but it would add at least a week onto the build process to order another tube, cut off the (or re-machine another) transmission mount plate, get it re-welded onto the new tube, and re-cut the tube lengths for installation. I decided to modify the car side plate and drop connector assembly on that side.

The car side plates were big enough to allow for relocation of the drop connector. I cut the connector plate off, smoothed out the car side plate, and tack welded it into it's new location based on the current length of the cradle tube. I then tacked the cradle tube to both connector plates.

There is about a 3 degree angle of the cradle tube to the car side plates in order to place the transmission flat on top relative to the car. Nothing is exactly flat in a 40 year old car - it's got character, without which, it wouldn't be interesting. I took all the transmission parts to Tony's house to get the 2 assemblies (car side and transmission side) welded separately with plans on test fitting, cutting, and tacking them together before coming back for final welding.

Stick welding rocks. Just as strong and pretty as tig welding, when done correctly, at half the price.

After everything was welded together, I cut the excess from the drop connector plates below where the cradle was welded. It would have been easier, not to mention safer, with a vice bolted to something, but what would be the fun in that.

The final product after a healthy coat of clear.

Installation is still a bit snug, but due to the complex design issues I think the mount came out great. I wouldn't try with less than a 2-stage assembly process due to the number of mount points. Make the car side and transmission side mounts separately, and then weld them together once you know how they're going to fit. Trying to do it all at once like the engine mounts would have proven difficult.

The transmission needs to be lowered in order to install the top nut of the isolators. This is going to be a pain when I replace them with self locking nuts.

The bombproof driveshaft I originally had made for the 280z by Drive Line Services in Atlanta was shortened by 1.5", rebalanced (without any balance weights I might add), repainted, and restickered by Carolina Driveline. They were able to do it next day and cut to my measurements. It fits perfectly and was the final piece of the car's driveline connections. The engine and transmission are so low in the chassis that the driveshaft is actually at a 0 degree angle. This was planned and test fitted prior to welding the 2 transmission mount assemblies together. In theory the driveshaft wouldn't need U-joints anymore, but along with being a bit excessive, even I'm not that convinced in the angle accuracy of the Droid app.