Manual Transmission vibration in 5th Gear

[PhantomLord]

My W124 E220's 5 speed Manual gear box was recently overhauled, it shifts and runs pretty smooth. But after certain speed (say 60MPH+) in 5th gear I can feel vibration on the floor of the car (sound's Burrr...), it gets worse with increased speed.

Vibration goes off if I remove my foot of throttle and I don't see it if I do same/more speed in 4th gear, can anyone please suggest what I should be looking into?

Thank you

[mbdoc]

We don't have that model here BUT....sounds like a drive shaft issue, does the drive shaft have a vibration damper? OR was there one & was it removed?

[PhantomLord]

Not sure if there is/was vibration damper, will get it checked. But there is no vibration if I do same speed in 3rd or 4th gear, does vibration damper play a role in these gears?

Thank you

[tom marshall]

Had a similar problem on a 300cd. Someone had removed the drive shaft, allowed the two sections to come apart, and put them back together out of phase. tom marshall

[tinypanzer]

Vibrations can be very odd things to pin down. To answer your question, yes it is possible to have a drive shaft vibration in one gear and not another, even at the same speed. For one, there is much more torque when you are in the lower gear. The extra torque could prevent the vibration, or in another instance cause it.


Harmonic oscillations are strange beasts, as there are so many contributing factors in setting them up. The bottom line is, if something gets excited at the same frequency as the resonant frequency, it will vibrate. The resonant frequency can be changed by almost anything. The weight, the mounting, etc..... It's like the classic opera singer cracking a wine glass stunt. If you excite the material at the same frequency as its resonance (or a harmonic thereof) the energy will start an oscillation.


So in other words, something has changed. I like the suggestion of the out of phase driveshaft coupling. Very likely. It is also possible that the flex joints deteriorated from being disconnected and re-attached.

Check all the rubber parts; trans mount, drive shaft mounts, differential mount, engine mounts, flex joints. All could possibly contribute to your oscillation.


-tp

[PhantomLord]

Thank you tom and tp for the input...

My car is at local MB garage, they are starting with dismantling and re-assembling the driveshaft. They have found drive shaft support bearing rubber cracked. Starting with replacing the rubber and support bearing first.

Will update the thread on how it goes.

[PhantomLord]

Got the driver shaft support bearing and rubber replaced. Now it drives bit smoother in 1-4 gears, but the vibration is not gone. Anytime I shift to 5th irrespective of speed the vibration is back.

So from past testing vibration is present from any speed between 40 - 180 km/h so I am suspecting this could be tranny issue?

[stevebfl]

Could also involve the trans mount. Aside from the dampening issue it also determines drivesahft angle