I think Bob may be dead on. I installed urethane mounts on the motor mounts
and
the tranny mounts and it causes a significant transmission of engine vibration
to the frame and it shakes the whole car quite a lot. I notice it a lot more at
idle but can still feel it at speed. There might be some resonate vibrations
that are getting transmitted at different speeds. Vibration due to imbalance
always increases with rotating speed, so I think an out of balance drive shaft,
even due to radial runout is not causing your vibration.
Gary
----- Original Message ----
From: robert k. smith <rksmith46@hotmail.com>
To: datsun guy <mantolik@oh.rr.com>; roadster list
<datsun-roadsters@autox.team.net>
Sent: Sat, September 4, 2010 10:16:41 PM
Subject: Re: [Roadsters] Vibration
hi mark, if you didnt notice a vibration before you changed the trans. mt.,
it seems likely
that the stiffness of the polyurethane accounts for the vibration. the softer
rubber mt.
absorbed the vibration before( thats its job). i suspect that after running
the car for a while,
the mt. might get flexible enough that the vibration might stop or lessen.
bob smith, ohio srl 311
> Date: Wed, 1 Sep 2010 11:41:24 -0400
> From: mantolik@oh.rr.com
> To: datsun-roadsters@autox.team.net
> Subject: [Roadsters] Vibration
>
> I had the engine trans out of my 70 SRL and noticed the trans mount
> was in dire need of replacement. I used the Prothane mount as it seemed
> the closest to the stock thickness. It was a fairly painless
> swap....but now I have this vibration that starts to be noticeable at
> about 40 MPH - it gets smoother as speed goes up but it is still
> noticeable....does not change with the clutch in or the trans out of
> gear and coasting. It is very apparent for in the 40-55 MPH range. My
> first reaction was to replace the u-joints, absolutely no change. So I
> am now wondering if anyone has a stock 5-speed trans mount they could
> measure for thickness? Mine was so far gone I could not salvage the
> pieces.....! Or could this be a drive shaft balance problem?
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