Engine These Vibrations Are Coming From Somewhere


New Member
Oct 14, 2003
I'm reinstalling the original motor into my '95 GT after having my 347 "fun". The orginal motor has been on a engine stang covered (bagged) for the last six years. Now that I've put the motor back in, I have a mystery vibration.

When the motor was pulled I felt it was fine, only 100K miles, and smooth running. The original balancer did die and was replaced with a 50oz Romac balancer. When putting the motor back in, I replaced the flywheel (50oz) with a cheap parts store brand, and installed a new Ford Racing HD clutch. Before, installing the trans I did notice the input shaft had a bit of "wiggle", but I hadn't noticed any significant tranny issues prior. When the vibration started I suspected the cheap flywheel and have since replaced it with a Ford Racing unit. However, when I was reassembling the car, I ran the car with out the tranny connected and experienced none, to very minimal vibration. I have since installed the transmission and now have this vibration I can't track down. Last night I took the serpentine belt off and ran the car a few minutes and the vibration was still there. This weekend I'll be pulling the flywheel and balancer to have them spin balanced/checked at the machine shop.

Not sure what else to check.
I do have poly motor mounts, but I don't think rubber would mask this. My 347 was on these poly mounts, and it did not feel like this.

How much play is the input shaft allowed to have? I saw someone (other site) mentioned the pilot bearing might not be holding the input shaft correctly, how else do you check this? I figured if the trans goes in and bolts up, you're good!?

Just listening to the car, it sounds...good, surprisingly good. No knocking, very smooth sounding. I just have this mystery vibration.

Can you all help?

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Apparently my ex-husband made that mistake.
15 Year Member
Jun 14, 2004
Acworth, GA
Ok, well this is a rare one, but sometimes there is a slight difference in weights between the pressure plate bolts. I've had to take them out and weigh them. Ended up having one that was a hair off, and had to shave it a little.