98 Rough idle and ride after motor and tranny mounts

Hi there,

Strange question, I had both motor mounts and tranny mount put in my mustang last week. I noticed right away when I got in the car and started it up that I could feel a crazy vibration in my seat and in the steering wheel that wasn't there before. While accelerating, I notice a large amount of vibration too, it seems to level out at higher speeds.

*These are anchor rubber mounts NOT poly***

What could this be? New mounts should take AWAY vibration, not add more.

I was thinking out of balance dirveshaft, but that wouldn't make sense for idling, and I know for a fact the driveshaft isn't out of balance (I swapped ujoints months ago, and marked location of bolts before removal), unless the counterweight is damaged.

Any ideas would help me.

I have it back at the shop, they are good guys, but I want to help them with ideas if they get stumped.

wmburns said:

It might help to include the model year of your Mustang.

Have you checked to see if the front crank damper has been damaged?

Has the crank damper or flywheel been replaced? Did you check to see if the correct balance type (internal or external) was used?

Click to expand...

Hey thanks for the reply. I don't know exactly what to look for. I don't think either of those have been replaced, and the mechanic I had to the mounts said it's probably out of balance internally. I'm not really fluent with internal workings of the engine. I have a 98 3.8L base convertible.

I know the original owner and there hasn't been any engine work in regards to what you've asked. Thanks again for the reply. Would taking pictures of anything help you with an idea?