Thread: vibration

High frequency could as you suggest point towards a potential tail shaft related problem.This caught my eye as I had a Range Rover that showed identical symptoms,however when the vibration came in a noise could be heard from the rear end.
After much frustration and trial and error it turned out to be the front tail shaft.The previous owner had replace the spline assembly but never had it balanced.
Hope this helps

Does sound like the rubber donut and is what i have described when mine went, rear ball joint is mainly noticeable over slow rough roads and when braking and or reversing.
I have a spare donut you can have as i'm retro fitting an earlier disco t/shaft with uni joint to mine.

Drop out the F&R drive shafts and check the universal joints, sounds like a dry or partially seized cross shaft needle bearing, the tailshaft at the donut end is centre spigoted to the diff pinion shaft flange so unless you have lots of unusual driveline backlash and noise/vibe under acceleration it would not be the cause of the problem, easily observed from beneath the vehicle to see if ok.

The frequency will help you track it down.

If it's wheel imbalance or run out it will be at wheel speed (say 6-8 times a second) at hwy speeds. I'd call this a fast 'wobble'. If a tyre has run out you may feel it at very low speeds as well (walking to jogging pace) as the tyre pushes the car around.

If it is a driveshaft out of balance or with run-out it will be 3 and a half times faster (say around 25 times a second).

If it is a driveshaft UJ it will be two times driveshaft speed (around 50 times a second). This is getting towards a slower 'buzz'. the rear flex joint would be somewhere between this and the one above for frequency (depending on how it is failing - check for cracks in the doughnut)

If your vehicle hasn't been lifted (ie. std height) and the front mass damper is still in place, it would most likely be driveshaft-related given what you've posted.

If it is lifted then I'd start by checking the front shaft as the driveline angles caused by even a relatively minor lift can cause vibration and early UJ death.

To check the UJs you are better off dropping the shafts out to check them (ask me how I know...). While in the vehicle they often remain pre-loaded to some extent and problems aren't necessarily obvious or detectable. Equally you can lock the centre diff and drive it with just the front and then just the rear shaft in to isolate which end it is.

Good luck

Thanks for all the suggestions! Minor update then. I removed the front drive shaft and could replicate the vibration on the drive to work, so safe to assume it's not from the front end. Everything looked shiny and new, plenty of grease. The harmonic balancer is still in place btw. As far as the suspension being lifted, I know the previous owner had heavier springs put in the rear not long before i bought the car, and it does sit a little higher in the back but I couldn't say by how much. I had mentioned that the vibration is nearly non existant with a load in it, thats what had me thinking about the donut. I haven't dropped the rear tailshaft out yet, that might have to wait for the weekend, but I did take the donut out and had a look. I can't see any cracks or anything else really that would make it the obvious culprit. Someone had suggested the ball joint only as a worn one may cause slight issues with the axle alignment and manifest itself as a vibration. Again I'll have to take a closer look but I have noticed there is a slight but noticeable feathering on the outside edge of the rear tyres that seems a little odd. I'm not convinced its an out of balance tailshaft yet as a previous car (pajero) had that issue and it was a constant vibe from 80kms, whereas this one only vibrates when I back off the accelerator regardless of speed, not noticeable under any sort of load. Btw, Loanrangie, I may just take you up on your offer, and maybe have a look at that uni conversion. Will PM you when I know when I have some spare time over the next few days. Thanks

No worries, could be the bush inside the donut and could also be bearing preload in the hubs.

update time, I caught up with Loanrangie over the weekend and got the donut he no longer needed. The one from my car and his looked identical but it was immediately obvious that the rubber wasn't the same. My old one was a much softer rubber and was far more flexible despite being identical parts from the same manufacturer. The only difference I could fine was the softer one had the number 9 stamped on it and the stiffer one had 10 on it. I hadn't realised there were different grades or types of rubber. Anyway, the replacement stiffer donut was fitted and thankfully no more vibrations are evident. It'll get a proper run down the freeway to work tomorrow and I'll be sure. Thanks Loanrangie for the donut and the chat!

Check the Big ball joint up the top of the rear diff. When it goes it puts the entire backend out of whack.

Personally, to me, it sounds like the doughnut is stuffed and the big ball joint is too. Good luck!