So I finally decided to try and track down the vibration a little more since I’m driving the Mustang more with my new job. It’s getting irritating on the highway. Since I was thinking the vibration was probably related to my “new” flywheel, pressure plate, or trans, I swapped back to all of my old drivetrain components last week. I’m running the 8.5” flywheel, old clutch and pressure plate, the 2.77 transmission, my old driveshaft, and the old starter now. I made sure to remember to put thread sealer on the flywheel this time too. Between that and tightening up the oil pan a little more (and maybe the different trans…), I don’t seem to be leaking oil anywhere near as much now.

The swap gave me mixed results. The vibration doesn’t shake the whole car anymore, so it’s a lot nicer at highway speeds. However, there’s still a lot of vibration in the shifter. It’s a little different feel than it was before, but that could just be a result of the different components damping it a little differently. The old clutch chatters a lot. The car drives pretty differently now—definitely different noises compared with the 3.03, a little smoother in a lot of ways, and it seems like when you let off the gas it doesn’t decelerate as quickly.

So yeah… mixed results. I’m wondering if I had multiple issues—something with the 3.03 transmission and the engine itself, leaving just the engine now. But I’m not sure at this point.