Whole vehicle vibration

Can anybody shed any light on why i'm likely to have a serious vibration problem at 50mph?

The whole truck starts to shake and its pretty much deafening if you dont have the radio up. Its not the death wobble, i've had that numerous times and know what that feels like. This vibration is a across the whole truck to the point the mirrors are vibrating etc. It almost feels like i'm driving on the rumble strip all the time.

I've started with the usual things first - i had the wheels balanced and checked, theyre fine, the king pins are fine and the brakes were sorted when it was serviced last week. The rear gearbox mount had gone and that was also replaced. The wheels have been re-balanced again (completely taken off the rims and reseated and balanced) by two seperate places in the past 3 weeks, but the vibration is getting worse. Wheel bearings dont seem to have any play in them either - in fact the fronts were changed mid last year along with the king pins and theres no oily marks from any of the wheels.

I'm thinking it could be the rear prop, I've had a poke round and it looks like the balancing weights are still on this and the UJ seems fairly tight.

The vibration starts just before 50mph and when you get over 60mph starts to quieten down slightly. If i dip the clutch or coast whilst driving (take my foot off the accelerator completely) it tends to go quiet, but the moment the accelerator is pressed, its back to feeling like i'm on the rumble strip again

Any suggestions please?

Dont think there should be any play in the uj's.

My mates FWD car done that when a driveshaft went, you could literally see the whole dashboard leaping around!!!! Not sure if it would be the same on a RWD.

Remove the rear prop completely and drive in 4WD High (ie. makes your car Front Wheel Drive).

If the problem goes then you have found the issue.

mlines wrote: Remove the rear prop completely and drive in 4WD High (ie. makes your car Front Wheel Drive).

If the problem goes then you have found the issue.

I did this and tried all sorts of combos and found it was the front prop. I had driven at speed with it in 4WD but the with front hubs disengaged between green lanes which was when I discovered the problem.

The other thing to check is that the rear engine (i.e. gearbox) mount is not knackered, as I had vibration issues with this as well.

I had a crawl under the truck with a torch and had a proper poke around - turns out its the UJ on the centre prop thats failing already have a replacement on order from CAM for £22 inc delivery - I did ring the main stealer for a price, but switched off when he said it was more than £280 plus the VAT :ohmy: :sick:

Its definatelt getting worse though, the drive to and from Dorset last weekend was just about bareable, the drive to Chesterfield on Weds the noise was deafening, but now its a case of being gentle until the new prop arrives. Interestingly, the centre props are different between jimnys, as CAM and me found out. CAM posted one out and i tried to fit it, only to discover it was slightly longer and the spline end a tad different and so won't fit - see pic, but correct one being shipped from CAM already - 5 stars to CAM for being super great.

I think thay are different between single cam and twin cam engines or manual and auto cant remember which