[ROVERNET - UK] riddle me this-sudden 3500s road noise

[Ron Morey]

Peter, This is where I would look. Check for a bad Ujoint in any of the 
axle(s) or drive shaft. There are 6 ujoints in total. Check also for any 
dents in any of the shafts. The slightest bend will be very annnoying. 
Usually a drive shaft problem will be worst at about 70kms (40mph) though. I 
have discovered also that I have one slightly bent wheel on my P6. This 
creates a vibration at 60-65 mph. The tires are probably slightly smaller 
circumference on the my P6 than on your P6B depending on the size you are 
using. So the speed is probably correct. The difference is that usually a 
bent rim shows at around 30 and only gets worse with speed. I cannot explain 
how this might cause a vibration at 45 with a second harmonic at 65. 
Exchanging the spare with the two rear wheels may help to locate the 
problem. Another thing you could check is the alignment of driveshaft and 
transmission. If the transmission sits too low or too high this may cause an 
alignment problem forcing the Ujoints to their flex limit and causing a 
vibration. Also if the transmision is occasionally rubbing on the tunnel 
this will cause vibration. One last idea on this tangent, pun intended, is 
to check for loose or broken motor mounts. The brackets that bolt to the 
block for the motor mounts are very difficult to tighten on the SD1 so I 
imagine the P6B is worse being a tighter fit. Hope this helps to point you 
in the right direction.
Ron.
 >From: peter king <peter at king-co.com>
>Reply-To: rovernet at lyris.ccdata.com
>To: <rovernet at lyris.ccdata.com>
>Subject: [ROVERNET - UK] riddle me this-sudden 3500s road noise Date: Mon, 
>03 Jan 2005 15:45:02 -0500
>
>Hello all.
>
>In anticipation of a cold weekend under the car, I wonder if anyone has an
>idea for what might cause a sudden occurrence of road noise and vibration 
>on
>my 3500s? I've determined only that it is not engine-related, as the
>vibration does not stop when I shift into neutral and coast. The vibration
>came on suddenly at about 60 mph, and now begins at about 45 mph, and is
>quite pronounced if I go over 50. Tires all look fine, but that deserves
>closer inspection.
>
>Thanks in advance for any recommendations you might have.
>
>Peter King
>
>
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