Thread: Help tracking down a vibration

I have a D2 V8 Manual. I have noticed a slight vibration after a lift (which from where she was sagged to is about 50-60mm). Dobinson springs, Bilstein stock shocks as recommended by Bilstein Australia and air bag helpers. The vibration got worse after castor correction of 3 degrees using trailing arm bushes (rubber and steel).

I assumed it was prop shaft related. It felt like it. I also had several other issues complicating things - buggered upper and lower balljoints, and delaminated front engine mounts.

I had Hardy Spicer do the rear shaft includinga new bush, spiggot and I put in a new GKN donut. I had them do the front shaft and balance it with new unis and new centre nylon ball...and took it back to balance again. This time they put on a much smaller german gaitor as the other one was potentially deforming at speed. I still had a bad vibration - less so with the front shaft removed and driving on rear only but still definately there. Driving on front shaft alone was very bad, but these things have such much backlash/play that having both shafts in is necessary to cut out most of the play and make it all smooth, so driving one shaft out and difflocked is not the best way to troubleshoot vibes.

Wheel re-balance and rotation made little difference.

I have now done ball joints, engine mounts, panhard rod bushes and steering dampner and they made a HUGE difference to steering and ride comfort. The truck glides over bumps at speed now...I cannot believe how much contribution the BJ's had to bump steer and crashiness. Also changed rear donut to another new GKN to see if that made a difference.

Anyway after the second lot of work - ball joints, second rubber coupling, engine mounts and panhard rod bushes the front shaft is back in and the truck is much smoother. There is however a slight residual vibration particularly when backing off at speed, but it can also be felt under hard acceleration at certain revs.

The first few metres of taking off from stationary I can feel what I can only describe as binding - it literally feels like the donut of a front uni is struggling. I am inclined to think that the raised rear is causing too much angle for the donut and it is squashing it a little.

I have done a fair bit of research and I think I can conclude 2 things - 1. The front double cardin shaft should not be an issue with a 2 inch or so lift and 2. There is debate about the rear shaft - some people say the donuts chop out very quickly, within 10,000k and that they are not designed for a lift; some say no problems (and that the D2 angles are not as affected by the lift as say a D1 with its A Arms). I know that the coupling is there to reduce driveline vibration, however it may also only work at certain angles - especially given the spiggot and bush arrangement...

I guess I am going to have to put up with it and when it gets worse address it then, but I suspect in time I might have to convert to rear shaft, rear uni joint.

The only thing not done is gearbox mount, but I cannot see that as being it...the vib is only through the floorpan and does feel like shaft!

I have check output housing for play - virtually nil (and it had a new bearing in there only a year ago). No play in front diff output, although there is a little bit more play/take up in the front diff than what is ideal.

If anyone has any ideas, please chime in.

Many thanks

PS. The photo in the avatar is stock height!

OK...this is getting old quickly. Shaft came back and went in. I am not happy about the condition of it, but that is another story. Vibration now less than immediately before it threw a uni cap, but still noticeable especially backing off at certain speeds and revs or accelerating through certain speed and revs. For example decelerating in third at 60 down a hill, Clutch in it goes away, clutch engaged rumbles straight back as (presumably) extra torque goes back through the shaft and its problems re-emerge. I have thought about housing bearings but both diff and output transfer case seem sound - no real play. I know there is some wear in the front diff.

I think the only thing to so is get a new shaft and go from there.

Two questions - does genuine GKN offer greasable unis as a complete unit and in any event where can I source a genuine GKN for the best dollars? If that goes in an no problems then clearl I can chase other things (...???).

Cheers