I'm having trouble pinpointing the cause of a vibration or shuddering in the driveline of my 240.It occurs when the trans.(BW55)is at the top of 1st and changing to 2nd. The rear busings are in good shape but the trans. mount and center bearing support seem marginal and I have yet to replace those.I'm wondering if it is more likely the driveline (center support,u joints or trans. mount)or the trans.slipping.

/// This sounds like u-joint trouble but it will cause vibration at the center joint. Has any one been in the drive line recently, the joints must be in phase. It is possible that a sagging mount puts the drive shaft out of position and you are feeling its' attempt to 'center up'.

Pull the rear shaft and feel the u-joints for frozen or loose bearing cups. While you're there check the rear end for play or noise when turning. If the front u-joint is bad the vibration would be felt in the transmission or gearshift. A bad u-joint will shake what it's near.

Last, if you don't find it put together a ear tube with a metal contact pin in the end and search out the noise on a lift while the car is running. Polybutyl water supply lines for sinks in 1/4 or 3/8th inch sizes are straight and stiff. A flexible piece of vinyl to connect to the ear will make it more useful.