Like the title suggests, I know that there have been a lot of threads about the poly trans mounts and the added driveline vibration that some people experience with them.... One of the many solutions to the vibration is to replace the poly mount with an OEM rubber mount - BUT, and forgive me If this is stupid to ask, when you do something like that aren't you just 'covering up' the problem? Shouldn't a drive shaft be checked-balanced. There are many guys out there with the poly mounts and they experience no to minimal added vibrations...
I am currently one of those guys who has installed a poly mount and at about 2500-3000rpm gets vibrations running through the car that I previously didn't have.... I can go back to the rubber mount, but I don't like masking problems if they do exist.
TIA
-Andrew

It could be that you're experiencing normal engine vibration. Because the poly mounts are harder they would transmit more vibration into car than oem rubber mounts.

- ever picked up a crankshaft, rods, pistons, drive shaft, tq converter, trans input drum, etc? steal parts all spinning at X rpm = "x" amount of vibration. There are no zero vibration motors/drivelines. Why do you think the factory used rubber mounts instead of just bolting everything directly to the frame?
- I do agree though that urethane mounts shouldn't make for excessive vibration. If they do, I'd be checking out what's causing the vibration.

I just replaced my stock mount witha poly one last weekend....I havent had anything that was out of the ordinary vibration wise

There's poly, then poly if you have a secondary cross member:

https://www.thirdgen.org/forums/atta...g?d=1130154497

JamesC

I'm running prothane's trans mount, with Spohn's trans relocation braket.
I will get the d.s. checked and double check my engine mounts... see if this makes a difference.
The new vibrations I can live with, just never noticed them before, and would hate to ruin anything due to a part that is "out of wack"...

-Andrew

Speaking of that secondary crossmember:
My 87 has a regular transmission crossmember. I just today, came across a dual crossmember at the salvage yard(crossmember and secondary crossmember). Anyone know if I can put the dual crossmember on my car without issues? I got the Hyperflex bushing master kit from energy suspension and it came with the secondary crossmember bushings. Hate for them to go to waste. Thanks in advance for any input.

I don't think there's a problem with bolting it up, but I don't recommend using the poly there. I've done it (as you see in the above link) and the increasesd vibration isn't worth it IMO--of course, no rubber is left in my suspension set-up, which, no doubt, also contributes.

JamesC

Thanks man.

I pulled my alum.d.s out and had it balanced - it was way out. What a difference now. I have continued to run the poly mount with no 'abnormal' or excessive vibrations.
-Andrew