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740 engine vibration[ALL/1998] posted by Calvin Baker on
Thursday, 25 September 1997, at 3:54 p.m.
The engine in my '91 740 begins to vibrate at about 2800 rpm. It is not a radical vibration -- just enough to be irritating -- sounds like a low hum at highway speeds. It seems to be worse under load. It is clearly an engine vibration -- it occurs whether driving or simply reving the engine with the transmission in neutral.
Any ideas on a cause?
Re: 740 engine vibration[ALL/1998] posted by Ed Lipe on
Friday, 26 September 1997, at 10:55 a.m.
Be sure to check engine mounts, bell housing bolts, trans mount and cross member. Check also for loose accessories; a/c compressor, PS pump, Harmonic balancer. Just for starters.
Re: 740 engine vibration[ALL/1998] posted by Brian on
Saturday, 27 September 1997, at 10:57 p.m.
If the vibration and noise occurs at one engine speed only (eg: goes away when engine speed is increased above 2800 rpm), then as a suggestion I would also check the exhaust piping and hangers to make sure everything is supported similar to the original installation.