Vibration problem

My 300 Disco suffers from vibration from about 50mph. Particularly bad about 60 especially just as you lift off a bit. Feels a bit like going over those rumble strips.
Both rear wheel bearings replaced after one collapsed few months ago. Rear shocks the same. Have been under it and can't find a thing wrong. All the bearings feel OK,A frame ball joint OK, no obvious play in U.J.s or prop shafts, no movement in any bushes etc. Rear wheels balanced.
Vibration comes generally through the body not through steering wheel or brake pedal.
I've been hoping it will get bad enough to find the problem but that will probably lead to it spitting a wheel across the M3
Any thoughts?

diver said:

My 300 Disco suffers from vibration from about 50mph. Particularly bad about 60 especially just as you lift off a bit. Feels a bit like going over those rumble strips.
Both rear wheel bearings replaced after one collapsed few months ago. Rear shocks the same. Have been under it and can't find a thing wrong. All the bearings feel OK,A frame ball joint OK, no obvious play in U.J.s or prop shafts, no movement in any bushes etc. Rear wheels balanced.
Vibration comes generally through the body not through steering wheel or brake pedal.
I've been hoping it will get bad enough to find the problem but that will probably lead to it spitting a wheel across the M3
Any thoughts?

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Is the vibration coming through the gearstick at that point, problems like this are usually drive line.

wheel bearings usually rumble and the noise changes as you go around corners, and different speeds.

Wheels usualy come in at certain speeds, ie, 30, then 60 but in between little problems, unless you have a buckled wheel or something of course.

Diffs tend to make a **** load of problems when you let power off, but a bad diff tends to howl, same with a gearbox, if it was as bad as that I would expect it to be noisey and vibration through gearstick.

Check engine mountings, gearbox mounts etc, and take off the props to check the ujs they might be foked, make sure there is also no lift on the flanges in both front and rear diffs and the gearbox both sides.

I have seen ujs that look ok but get them off and they are foked.

david451 said:

Is the vibration coming through the gearstick at that point, problems like this are usually drive line.

wheel bearings usually rumble and the noise changes as you go around corners, and different speeds.

Wheels usualy come in at certain speeds, ie, 30, then 60 but in between little problems, unless you have a buckled wheel or something of course.

Diffs tend to make a **** load of problems when you let power off, but a bad diff tends to howl, same with a gearbox, if it was as bad as that I would expect it to be noisey and vibration through gearstick.

Check engine mountings, gearbox mounts etc, and take off the props to check the ujs they might be foked, make sure there is also no lift on the flanges in both front and rear diffs and the gearbox both sides.

I have seen ujs that look ok but get them off and they are foked.

Click to expand...

Just one other point, and although you have had the wheels balanced, rotate them and look at them both from the side looking at both the wheel and tyre, and then the surface of the tyre. You are looking for bulges or lumps, it is possible you have a distorted tyre on the vehicle.

Coulda thrown a wheel balancing weight.

Thanks for that guys. I don't think it's balance since re-balancing the rear wheels had little effect and if it was fronts, I would expect to feel it through the steering wheel.
I think tomorrow the prop shafts are coming off and if they're OK I'll take the wheels off my restoration project and try them. That should isolate that problem. It doesn't really sound like transmission/bearing issues but I've been wrong before.