Transmission Mounting -- What shear load?

[JFBrink]

Hey, there,

I want to use a pair off-the-shelf industrial vibration isolators to mount my Miata transmission to the crossmember, but I am really uncertain as to what load range I need to be in.

Does anyone have an idea of what the shear load ratings for an OEM or aftermarket transmission mount would be?

I'm guessing high -- I can imagine the torque being translated into a significant lateral shear motion. But, I may be totally wrong about this.

Anyone have any thoughts (and/or data) on this matter?

Thanks,

Jesse.

[fj20spl311]

WHY?

Just go to PEP BOYS and get a "universal" GM, Ford, Dodge..... trans mount.

They should have a trans mount that can easily be modified to fit for $10-$20. Just ask to look at the pictures.

That's what I did for my FJ trans.

Phil

[ppeters914]

...or the Energy Suspension GM mount that Dave "I'm doing dizzies now" Brick showed would work for a regular roadster tranny.

[JFBrink]

The "why" is twofold.

One is that I've already drilled my holes through the x-member and they don't match universal mounts. I actually had a nice solution using the stock Roadster tranny mount, turned upside down, but I made my template while sleep-deprived by my new-born and ended up drilling to the wrong dimensions. For a variety of reasons, I cannot drill new holes.

Two is that the Universal, GM, Ford and even Roadster mounts all push the Miata transmission up very high, because they are now sitting on top of the x-member, creating a significant pinion angle.

Cylindrical industrial vibration isolators solve both problems.

So... any thoughts on shear loads?

Thanks,

Jesse.

[nomadtrash]

There isn't a lot of load in the tranny mount. Almost all the load goes through the motor mounts. The tranny mount just keeps it from bouncing around back there. Just about anything you put back there will work fine.

[datsunrides]

Wouldn't shear be more fore and aft? I think the trans mount works in tension/compression (up/down) for the most part. If you can get vibration isolators with 5/16" studs, that should more than suffice. May want to get a couple if the rubber used in them reacts badly with oil or make sure they are rated for contact with oil. Hell, you could probably get away with some old swaybar bushings if you wanted to be real frugal.

Mark