[Roadsters] Vibration

[Mark]

  Thanks to everyone that has responded to so far!
Here is an update:

I am positive that phasing is correct - though it was off some 
originally.   It is a bit better - still noticeable in the 40-55 mph 
range.  I have looked closely at the condition of all the components and 
feel everything is as it should be.  I agree about the balance issue - 
it should keep getting worse as speed increases.  Someone on the list 
volunteered to send me a used original mount that is serviceable.  I 
will try it when it arrives this week.
I also have urethane engine mounts on this car.

Will let you all know after I try the OEM unit.  I really want to stay 
with the urethane mount if possible - so if it is just mount related, I 
will most likely swap back and live with it...

Mark
-Ohio



On 9/5/2010 12:53 AM, Gary Boone wrote:
> 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 at hotmail.com>
> To: datsun guy<mantolik at oh.rr.com>; roadster list
> <datsun-roadsters at 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 at oh.rr.com
>> To: datsun-roadsters at 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?
> ________________________________________