Hello!

The car is 940 GL / 230FB / M47 Trans. I have a issue regarding vibration which i cant seem to fix or diagnose on my own. Whole car starts to vibrate from 40mph to 60 mph, it smoothes out at about 60 mph, making it less noticeable but itīs still there. Itīs speed related, changing gear or dumping the clutch makes no diffrence. Thereīs a judder/hopping in first gear when taking off, if that means anything.
There are some faulty parts on the car which i havenīt changed but i dont think those can cause such symptoms: Front strut top mounts, Right inner tie rod. (Theres no shaking in the steering wheel when the vibration occours).

Hereīs a list of what iīve changed so far, which mostly made little to no diffrence:
* New prop center bearing
* New prop u-joints
* Diff oil
* Gearbox oil
* Front wheel bearings
* 4x new brake discs, pads, caliper fix kits.
* Tires are brand new (Driven 1000 km), Balanced in 2 diffrent shops just to be sure.

 

Sounds driveshaft related - are the two driveshaft sections still original and aligned correctly? Should be markings to line up the sections.

The "judder/hopping" when accelerating in first gear could easily be from the driveshaft - Don't remember the 940's as well as I do the 240's - on a 240 when the differential bushings, especially the upper control arm bushings would wear out - the diff would twist toward the ground when accelerating forcing the Ujoint at the diff into a bad angle - causing vibration problems.

On a 940 the bushings in the green squares prevent the diff from twisting under acceleration. On a lift - pull the driveshaft up and down at the rear ujoint to see how much movement is allowed by the bushings.

 

@hoonk
The Driveshaft is not original, itīs taken from a 745, but it is aligned correctly. I still have the original driveshaft too but the problem was same with that one.
I dont really have access to a lift to check those bushings in such manner, have to wait until i can use a buddys lift. The vibration/noise is not affected by acceleration though, itīs there all of the time at those specific speeds 40-60 mph, doesnt matter if the car is in neutral or anything it still makes the rumbling noise/slight vibration. At first i thoguht itīs the diff but cant really be, little to no play in the diff, the car has original 173,000 km (107,497mi). Also new oil in diff now, there was 0 metal shavings on the magnet.

 

Woring control arm (rear) bushings will aggrevate the judder when first accelerating. I trust the alignment pin and bushing is there on the front rubber joint. And I would make sure the driveshaft is in a straight line -

 

@hoonk I finally got time to check the rear control arm bushings, the play is very minimal, bushings are in great condition. Also checked the gearbox mount, which moved up and down about 1 cm max, when i pulled on it with force.
Alignment pin and bushing are there. I moved the center support bearing downwards 6mm to get the propshaft in a straight line, which made no diffrence at all to the noise/vibration (the car is not raised or lowered).
Took the car for a longer drive today, trying to listen/feel the exact area and it seems like its more of a resonating noise which fills the whole cabin with very very slight vibration in the drivers seat.
I jacked the rear up in the air and spun the rear wheels, it makes a clicking/metallic sound of some sort with every rotation, iīve attached a video with the noise. Then i checked the bearings for play, theres 1mm of play when i move the shaft in and out, iīve attached a video of that too.
Could it really be the rear wheel bearings which resonate noise and slightly vibrate only at 60 kmh up to 120 kmh (37 mph to 74 mph) ? The noise / vibration goes completly away at 120 kmh, the car drives like new at that speed and under 60kmh.

 

Hey there, I have not had your problem so this is a guess... The second video definitely shows enough play to warrant bearing replacement. The bad bearing could sound like that.