XJ Mods VSB 14

[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,

[rainman]

have you tried taking the steering dampener off? see what happens.
you can also get it up on stands see if you can reproduce the vibes.

[alexbrown64]

Originally Posted by rainman

have you tried taking the steering dampener off? see what happens.
you can also get it up on stands see if you can reproduce the vibes.

I'll do both those things in the morning. I have jack stands and with the rear drive shaft off, i can just raise the front and give it a bit and see whats going on..

Cheers,

[alexbrown64]

Ok,

So early this morning i put the XJ front end up on jack stands.
The rear shaft is disconnected. Hand brake on and chocks.

First i spun the wheels, then wiggled them etc.. smooth as silk as there is all new wheel bearings and unis in there.
Then i checked all the steering, tre, etc.. and all smooth.

I started her up and run it up to 90kph. Smooth as silk while jacked up. No vibes through steering, no noises. While she was in drive and the wheels were spinning i put a block of wood as close to the tyres as possible when spinning. The front right seems to have a 2-3mm high/low spot, while the left seems to be about 1mm. These are brand new Maxxis Bighorns 33" at 40psi. Remember, is said the car seems like its driving on a corrugated road.

I then got under the car again. The new front Olivers drive shaft has a minute amount of play in the cardan. Probably half a milimeter, but i would say there should be none. I have had problems with the center ball on these shafts.
I had emailed Tom Woods and got a reply last year saying it was a known problem that there was an issue with the greasable and non greasable center ball. He recommended to use the greasable center ball but cut the rubber boot and metal holding ring off, as these can bind the joint at angles. I opted to put my old non greasable joints in.

So, at the moment i think i have tyre and drive shaft issues.
Dropping the kids at school and then going to the tyre place i got the Big Horns fitted at and see what they reckon.

Cheers,

[oldon]

Have you dropped some tyre pressure & tried it? 40 psi is a lot of pressure in a big tyre on a relatively light xj even though you have added lots of accessories. Only my opinion Alex, but I'd try them at 30psi go for a run & use the 4psi guide. Tyres need to flex a certain amount & I think at 40 yours are probably are too hard. Since you solved many other issues so far, this one won't beat you.

[alexbrown64]

Thanks Oldon, i took the XJ to the tyre place and they ripped all the wheels off. They aired them down to about 34psi. They also re-balanced them and gave them the thumbs up. The balance was a bit out as the reckon they have settled on the rims a bit now.
Airing the tyres down and the balance has made a bit of difference but there is still something going on.

I took the front shaft off and put it away. I took the rear shaft and put it back on.
This has made a big difference and feels a lot better at 90/100kph. Not many vibes at all now.
However, there is STILL some noise coming from the front even without the shaft. Its like a rumble. When it was jacked up at the front it seemed quiet. On the road its noisy. I am beginning to think the carrier bearings are worn, or something in the diff is rumbling.

On another related note.. my Olivers heavy duty driveshafts had binding issues related the the center ball. There just wasnt much articulation (about 20*), and in fact when i was driving last year, the cardan section actually chewed the metal ring and rubber seal up.

To get around it, i used the center balls from my old shafts which have more clearance and allowed the shafts to articulate.

I have been trying to find out if the greasable and non greasable center ball yolks are interchangeable. I have read some places that they are not. In fact, when i pulled my Olivers drive shaft off today, the ball seal had been ripped off.

Also, i had another look at the greasable center ball that Olivers fitted, and that was giving me issues. It is not genuine Spicer. Its an aftermarket one with no markings on it. The genuine looks like this....



That may be the reason for the original rubbing. Slightly different casting which may be rubbing.

OK, so i think i am dealing with multiple problems. Noisy diff, noisy shaft.
Will keep working away to get it resolved.

cheers,

[Richard buttocks]

40psi makes my 26psi look very low

Have you tried it without both shafts?
Rule out the transfer etc?