[alexbrown64]

When the kids were little, i ripped out the headrests and put those DVD player ones in. I chucked the old headrests out. Now the kids dont use the players anymore so i found some new headrests up the other side of town. Gave me a chance to do a long run in the XJ today.

This is where i need some help......

My yellowbox speedo calibrator was out a bit, as i checked it against my gps speed. This was throwing my gearing calcs out a bit. I did some experiments on the freeway and she goes 65mph/105kmh for 2600rpm. The motor actually purs at this rpm. I also did 80kph and dropped her back to 3rd where the rpm was around 2700/2800 and the motor sounded great.

I am actually thinking of leaving the 4.88 gearing as it seems the motor likes it at all speeds and she is not over revving.

My problem is something else!! I have a very bad vibe at all speeds.. from 1 kph up to 105 kph.. exactly the same vibe. I thought it was the gearing spinning everything to fast, or the mud terrain tyres, or the Brown Dog motor mounts.. but i think its something else??

The XJ has been running great but it has felt very agricultural for a long time. Almost feels like your driving a Bobcat, or driving on a corrugated road.

First the problem:
I test drove around my street from 1 kph up to 40 kph and the feeling is the same the whole time. Vibration through steering wheel, no whine, chirps or groans but there is a noise, like a car going along a corrugated road.

This feeling and noise goes right up to freeway speeds as well.. horrible.

I took the rear drive shaft off and everything is still the same. I also did the following tests with no rear drive shaft...

At 10kph i put it in neutral and shut the motor off.. the vibes and noise stayed the same until the car rolled to a stop. There were vibes coming through the steering wheel and still that noise of a car going along a corrugated road. It seemed even worse at about 1-2 kph just rolling without engine on!! I thought it was my Brown Dog motor mounts..... but it cant be.

The 33" Bighorns are brand new fully balanced on new pro comp rims.
The brakes are brand new.
The front bearings are Timken and almost new. Axle unis new.
The drive shaft and diff are almost in line so there is no bad angles to get vibes (at the expense of my castor for steering).

The drive shaft is a new heavy duty Olivers shaft, balanced etc with all new uni's.

But.. i did have trouble with both shafts as they came with greasable balls in the cardon joint and there was some binding at large angles. I swapped out my older style ball joint from my old shafts to get a better angle. If you read this thread back a few pages it explains the problem.

So.. at the moment its trial and error. I will take the shaft off the front and put each one on the back to see if there is a difference to eliminate the shafts.
I will rotate tyres and even swap them for a set of spares i have to eliminate that.

Can anyone think of anything else that could cause these symptoms ???

I think its been like it for a long time, but not sure when it really got bad.

Cheers,