\Have started to notice a low frequency vibration that I can hear more so than feel, MOST prevalent at 75mph to about 80mph. It’s extremely noticeable on smooth road, but pretty noticeable as long as it’s not an awfully paved road.
I’ve replaced the entire driveshaft, flex disc, CSB a little over a year ag, along with engine mounts and trans mounts a few months back. As far as I can remember, 75MPH was always a very smooth operating range until recently.
There seems to be a similar noise when coming down through 40MPH, but I can’t tell if it’s the same or just exhaust.
The noise seems to be there mainly when maintaining speed & decelerating, but SEEMS to not be there under moderate acceleration, but that could be due to engine noise before the car shifts up. Under light acceleration, I can’t tell if it gets better or not
The noise is still there if I put the car in neutral at speed. It dissipates once below 70ish MPH no matter what gear, or state the car is.
I do know that my diff bushings are very much on their way out, as evidenced by the dry rotting I can see on it, as well as the clunk going from R to D and D to R, if that’s any help. I wonder the U joint angles aren’t happy with this, and if the noise is being transmitted more so to the front of the vehicle.
It seems to be coming more so from the front of the car, within the dashboard, so I don’t think it’s my CSB, or flex disc (also, like I said, those are newer). I wonder if my trans mounts either were tightened down too far, or not enough - I couldn’t access them with a torque wrench, so just used an open ended.
There’s also a chance that while my wheels balance fine, once of them may have a shimmy in it. I’ve had all 4 re-straightened at the advice of a shop when I first bought the car. All the driveline stuff has been done by me. Tires are only just over a year old, with under 10k miles on them.
Any insight ? Would looooveee to avoid having to drop the driveshaft again, and am planning to do the differential bushings sometime in the next few weeks, but damn, it’s been hot hot here in NYC and all I want is a smooth, quiet ride again.
Bonus - moderately - clean engine bay photo