It lives, it vibrates

[GRMPer]

I've now put about 30 miles on our 1969 911e, but there's quite a bit of vibration from 2k-3k. I've isolated it to the unobtanium transmission mount...which looks ok, but when removed and the tranny is supported w/ a jack, the buzz goes away.

So...I guess I'm wondering if I have the right combination and orientation of washers?

chassis, large washer cup upwards, mount, large washer cup downwards, bolt.

Should there be some smaller washers in there as well, to keep the large washers from creating a solid mount?

If there isn't...I might just put some in there and try it.

Per

[nick-moss]

Look like small washer, large washer (concave out), mount, 2nd large washer (concave out)

[GRMPer]

Hmmm...thanks!

Is that a common failure mode for the tranny mounts, to transmit a lot of vibrations in the mid range?

It would make sense, as it would essentially create a solid mount as it collapses.

While I have new engine mounts on order, the tranny mounts are not available. I wonder if I can "fake it" by using a small washer between the mount and the lower large washer, essentially spacing the large washer away from the mount as if the mount was still in good condition. Pelican has the crossbar, but sheesh...$700+ !! I might risk the investment of $0.20 in washers instead.

Per

[sithot]

Did anyone see the PMO article attached to their add in Pano or Excellence (can't remember which) written about solid motor mounts. In a nutshell, the writer was against them. Made sense to me but I've always left well enough alone so it didn't apply.
It made for a good read, though.

[GRMPer]

Well...new engine mounts didn't solve it, but they did make the whole car quieter. I wound up doing something pretty sneaky w/ the tranny mounts, I took the crossbar from a 915 and redrilled some holes so that it lined up with two of the studs on the 901 box and removed the other two studs, the 901 can then be drilled/tapped for the other two existing holes in the 915 crossbar) anyway, that at least allowed me to see if it was in fact the tranny mounts that were causing the vibration (or failing to isolate it). Nope, that didn't help either.

So...engine came back out today, and I'll take the flywheel and pressure plate to a machine shop for balancing.

On the positive side, I heard something about early 911 starters being available at Autozone and Napa...my local Autozone had a remanufactured Bosch starter for $41.99. Looks good and the gear clicks back in completely, unlike the starter I returned as a core.

Per

[GRMPer]

It turns out that waaaaay back when I first got this used flywheel, before the teeth got chewed off of it by a bad starter, I had it resurfaced. You'd think that a machine shop would cut the flywheel "true". Nope, friction surface and where the pressure plate bolts was completely off, to the point where the flywheel was junk.

It's a shame, because the later machine work where a new ring gear was welded on was absolutely, spot-on perfect.

New flywheel on the way.

Per