driveline vibration/ 94' Q45

[ckau]

in reference to a 94' q45, over 200 thousand well maintained miles, timely serviced. Just now starting to see a few problems develop. There is a harmonic vibration in the drivetrain that comes in at approx. 1700rpms and will fade away around 2200 to 2500 rpm. This vibration is getting worse. During hard acceleration, the vibration lasts through the rpm window quickly but is noticably harsher after and will settle down after some normal acceleration. Drive shaft connections? Any suggestion as to what I should focus on?

[Q45tech]

Periodically one replaces the differential mounts [rubber isolators], transmission and engine mounts to correct for SAG.

Eventually the driveshaft will need to be replaced as the internals [foam core] may shift.

One must specify gear number and speed along with engine rpm to get drive shaft rpm to correlate with vibration intensity and frequency.

[goody90q45]

........There is a harmonic vibration in the drivetrain that comes in at approx. 1700rpms and will fade away around 2200 to 2500 rpm. Any suggestion as to what I should focus on?

Transmission mount (AKA 3rd engine mount) and the pair of exhaust hangers mounted to it. If they've never been replaced they're due. After that then look at the two engine mounts and the drive shaft (if it's been removed in the past).

transmission mount R&R is an easy DIY and the only special tool needed is a 2nd jack to support the rear of the transmission while the mount is being replaced. Do a couple of searches (transmission mount, transmission mount, exhaust hanger) and you'll find all the info needed to complete this job.