Engine & tranny mounts

[Phils69]

I have been running the hard polyurethane motor and tranny mounts for a while. I am getting a vibration thru the car which seems to match the engine / driveline rpms. I am thinking about changing to stop this. I put these on for the strength but i am tired of the feel. I am assuming because they are so hard if I change to a softer mount it may help. Please let me know what would be a good replacement to help eliminate this. I am running a 408w and c4 tranny. Thanks

 

[65fastbackresto]

Maybe just go back to stock rubber mounts? Would be pretty cheap and easy fix.

 

[Phils69]

I think I'll try replacing just the tranny to start to see how much difference it makes. I wonder if the local parts store mounts are ok or should I go to a stang parts supplier?

 

[65fastbackresto]

Your local parts store can usually order them cheaper then a stang supplier. At least mine does in most cases.

 

[Hack]

I had poly motor and trans mounts in my '89 Mustang and I only noticed the difference between them and stock mounts at idle (sitting still). Are you positive that you are only noticing a characteristic of the poly mounts? I think something might be out of balance if you feel vibration going down the road. Also, if you have a built 408 you might have some strength issues if you run stock mounts. At a minimum you should probably drill through them and install bolts to prevent them from separating. I ended up with rub marks on top of my intake from the motor twisting on my '89, and it wasn't making a ton of power. I'd hate to see you dent your hood or scratch something after the stock mounts separate. However, if you want to run them, they are cheap and easy to find at most parts stores.

 

[Phils69]

I'm going to just try the tranny mount to see if it gets better. The 408 is not a racer but it's built fairly stout. I'm going to keep the hard engine mount for safetys sake. I had to have a driveshaft made when I put the driveline in 6 years ago because I went with a c4 to replace the fmx. I pulled the driveshaft again about a month ago and it runs true and the joints look fine. The 9" rear is original with just a oil change. Could anything in the rear cause this shudder vibration?

 

[Rusty67]

Poly mounts, and solid mounts even more so, will transmit vibration that a rubber mount will absorb. If you have a problem in your driveline anywhere, a poly mount will make it far more apparent. Even when everything is perfect, you will get much more vibration with poly mounts when compaired to rubber. The trans mount will transfer more driveline noise but I can't stand how the trans flops about with the rubber mount.