That being said, my helper and I put on our dirties and headed outside.. Now, my helper kept dancing to the "boy music" coming from the garage, so he wasn't worth much. In the end, I alone handled the dirty work. I started with the trans because mine was suffering, and as a feeler for swapping the motor mounts(in the same sitting). Here are my findings.
Pros: Stable as L. Feels great at speed. Everything I want because of my tight fitting exhaust and the fact that I like to flog the car on back roads.
Cons: Mucho vibration transfer to the body at low speeds and idle. A lot more than expected.
The Breakdown:
I was amazed at the detailed vibration transfer that just the trans mount brought to the table, high and low. So much detail that I could hear things that I couldn't before the swap.
On the high end, while running through the gears, I could even hear a faint wind up of the internals of the transmission!
At idle there is a low resonant rumble, somewhere near the 50Hz range. It sounds like a bad sub hum. But its all around you, and loud. At least for my build concept. And I'm no nancy boy.
I could certainly get used to the changes, but someone jumping into the car for the first time is going to feel like they are in more of a race prepped car than a built street car.
My biggest concern is the power that those low frequency vibrations have. I don't want things to start coming loose all around me. Over time, that resonant vibration could certainly create issues. And I don't feel like chasing my tail..
I think I'm going to score a 320 mount and swap it in for comparison.
OK, so. I swapped in the 320 mount and its MUCH better.
I had to drill the crossmember to accept the larger m10 stud, but other than that its straight forward.
The result was what I was after all along. Firm and stable. But you can certainly tell that the rubber is more flexible, the exhaust is tapping the floor pan/heat shields again. So I'm gonna have to do some old school massaging...
