Transmission Mount, solid vs hydraulic height difference, & vibration

[ChameleonGreen]

I've been trying to locate the source of my very annoying highway vibration. Sometimes it starts as early as 45mph but not usually until 55-60mph and then just gets worse. I had my tranny rebuilt a little over a year ago and because they couldn't directly bolt on the ES Poly mount they threw on a universal one (but they did add the shim plate that comes with the ES mount). I didn't really care until I got fed up with the vibration. I don't know if the vibration started after the rebuild, but I replaced the mount this afternoon (minus the ES plate) with the $17 Auto Zone solid V8 mount. It looked very similar to the universal one, but I was mainly comparing height, and they were very very close to the same. When I was at Auto Zone I compared the height of the hydraulic V6 mount to the solid V8 mount. The V6 one was about 1/2" taller than the V8 one. After I replaced the mount the vibration is still there, but it does feel a little smoother if that makes sense. Maybe a difference in the grade of the rubber? So anyway, down to the real question. Would the difference in height between the V6 & V8 mounts cause highway vibration since I'm not at stock height? I don't know if it would throw off the angle of the driveshaft enough to cause vibration. Any other related causes? The vibration stays with the tranny in neutral and car at speed.

97' V6 A4

[RadRacer]

Re: Transmission Mount, solid vs hydraulic height difference, & vibration

Is the whole car vibrating or what? Ever think that it may be your tires?

[FirebirdGT]

Re: Transmission Mount, solid vs hydraulic height difference, & vibration

Maybe a difference in the grade of the rubber?

Would the difference in height between the V6 & V8 mounts cause highway vibration since I'm not at stock height?

I don't know if it would throw off the angle of the driveshaft enough to cause vibration.

YES

YES

YES

[ChameleonGreen]

Re: Transmission Mount, solid vs hydraulic height difference, & vibration

Is the whole car vibrating or what? Ever think that it may be your tires?

Rotate, balance & align just done. No effect on vibration, but it did make my car feel like it was teetering like a bike with training wheels. The teetering effect happened last time I took it to Firestone too. I have lifetime align, balance and rotate and I take my car to a different Firestone each time to prevent one dumbass doing a crappy job each time. The teetering must have something to do with whatever is vibrating. It does feel like the whole car is vibrating, but the source seems to be the driveshaft.

[ChameleonGreen]

Re: Transmission Mount, solid vs hydraulic height difference, & vibration

YES

YES

YES

Then;

Since the stock V6 mount is 'hydraulic' can I assume that it compresses under weight of the tranny? If yes, under dead load (car parked and not running) does it compress down that 1/2" and essentially become the same height as the solid? If yes, then I'd expect the problem to be something else.

If not, why is it called hydraulic?

Also if not, is it safe to just add 1/2" of washers to each mount bolt between the tranny & the mount or do I really need to just stick with the hydraulic one?

My car is a lightly modded daily driver. I don't have a problem with it breaking so I don't care which mount I use. I just want a smooth ride again.