Vibrating Shaft Fixed at Last!

For quite some time now, we’ve been having a crazy vibration issue on Moby and it was driving us nuts being that it would only show up under very specific circumstances that made it hard to track down. Of course, anyone who knows me knows I would never do it BUT – hypothetically speaking, IF I were to let off the gas and decelerate from about 90 MPH, the front wheel drive shifter on our Atlas 2-Speed would vibrate aggressively and to the point where it would make a loud audible buzzing sound. At any other speed, everything would run nice and smooth and without any issues. So, for the longest time, I had assumed this was a problem with drive shaft balancing, pinion angle, blown control arm bushings that were allowing for too much pinion drop or even a failing transmission mount. And, as you can guess, I have systematically and thoroughly gone all of these things, each time thinking that I got it for sure. I rebalanced my drive shaft and more than once, I rebuilt my control arm bushings even though they didn’t need it and I purposefully adjusted my pinion angle high and low and everywhere in between just to see if any of it would make a difference and… nothing. At one point and time, I found I had lost a transmission mount spacer and thought for sure that replacing it would fix the problem – still nothing! After a while, I kind of just gave up looking for the problem being that I would only feel it under that previously mentioned hypothetical situation. But then, after doing a recent run up Fordyce and clearing some weights off the drive shaft, I decided to have it rebalanced. After pulling the shaft, Cindy mentioned that I should check the output shaft flange nut. She said she remembered reading something about the importance of it being tightened to torque spec to help prevent vibrations. Needless to say, I set my torque wrench to 150 ft. lbs. as is the spec according to Atlas, put it on the nut and… sure enough, it was in fact loose!!! After seeing this, I decided to pull the nut, check the o-ring, clean up the old RTV, applied new RTV to the base of the nut and reinstalled everything as required. After getting the drive shaft back from balancing, I installed it and after taking it on a test drive, I found… the vibration was GONE!! er, I mean, the vibration was most likely gone being that I would have needed to get Moby up over 90 MPH to know for sure.

Anyway, I just thought I would share this story with you just in case there’s anyone else out there who might have an Atlas 2 with a vibrating shaft or shift knob.