Re: Vibration - accelerating in 5th gear in 1993 7 (archive)

Interestingly enough I have the identical problem my car seems to stop vibrating ater ten miles or so. It also doesn't do it all the time. It must be something inherent to the car for us to both be having the same trouble. Mine car is heading to the dealer soon but I will hold off for any possible insight 93 740il 90k
Hoping someone has suggestions here... When accelerating in top gear (5th) in my 1993 740i at 45-60MPH "after" the lockup torque converter has engaged, there is a very noticable vibration when attempting to accelerate. The vibration seems to come from the rear of the car. The strange thing is, if I am going 45-60MPH in 5th and lightly accelerating BEFORE the lockup occurs, the vibration is not there. Then, suddenly, when the RPM's drop with the torque converter lockup, the vibration immediately begins. Another strange thing, it doesn't always do it. It is sporadic. It also does NOT do it in any other gear.
Other facts... the car has 102K, the tranny seems solid - it shift correctly - indicates no fault. Could it be a Kwibo joint or other drive shaft component? Maybe the harmonics of that certain RPM (around 1500)in 5th cause some sort of driveshaft vibration? Anyone heard of anything or had a similar problem? Also, for those that are interested, my car runs beautifully on the ORIGINAL M60 motor with 102K. It is however, a northern California car that always had 92 octane fuel (read lower sulfer levels). I like this car more than my 97 M3 (Well, I drive it more - must be the stereo and the comfort). Any help here will be returned when I can share an experience. Thanks!

I have simular problems with my 92 740i 95k but in
my case it's speed related. It was a while after I bought the car when I first heard the noise. I went to a dealer and found out that the whole engine was loose. They replaced the rubbermountings at the engine and trans. That didn't help much so I had to replace the propeller shaft. Then it went much better but I still have a noise. The vibration appears at about 50mph and again at about 70 with a higher frequency. The noise is loader when the car is cold but if you listen carefully you can hear it even after an hour of use. Sometime the noise is load and the next day it can be slight.
The noise at 50mph is the same no matter if I accelerate or set my trans to N and float. At 70mph it's a little higher when accelerating.

I did some calculations and I think the noise (about 20-25Hz)is related to the propeller shaft which is rotating with 1200-1500 rpm at the above speeds. Perhaps is the chaft my dealer replaced, defect.

I would like to hear from others who had simular problems and maby know a solution.

Lars from Sweden.

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