This could be a lot of things related to balance and harmonics. Bent
wheels coupled with crank out of balance etc. But consider the engine
rocking on it's engine mounts and the exhaust hitting the chassis under
the driver's floor. Is the vibration a 40 mph regardless of gear thing or
is it a certain RPM in any gear thing, this will change probable cause of
the vibration.
James Nazarian
'71 B roadster
'71 BGT rust free and burnt orange
'74 BGT going by-by soon
'63 Buick 215
On Mon, 13 Dec 1999, John R. Boehmke wrote:
> As I knew would happen, I'm slowly replacing everything on my 77B engine.
> I've rebuilt the carb, new choke, water pump, timing chain, tensioner, and
> all the assorted tune-up goodies, but there is still a problem. When I get
> to about 40 mph in high gear, a strange vibration starts. If I push in the
> clutch it goes away, and comes back when I release the clutch. If I rev the
> engine with the clutch in (while going 40mph) I can get it to stop, and the
> engine will run past 40 without the vibration. If the problem were in the
> drivetrain or suspension, I would assume the vibration would remain, even
> with the clutch depressed. Also on a 100 mile trip, it went through a quart
> of oil, but don't ask me where it went. This doesn't happen all the time,
> and below 2000 rpm it runs great. Could this be bad main bearings? (The
> engine has 92,000 miles on it) If this is the case, winter in Montana is
> not a bad time to have the engine out.
>
> Thanks in advance for any ideas.
>
> John
> 77MGB etc.
>
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