Thread: Not good vibes!

Originally Posted by POD

Sorry but that is incorrect. Raising the vehicle decreases the caster angle by rotating the axle forward, resulting in approximately zero caster with a 2" lift, instead of the required 2 degrees positive (from memory) caster. This results in poor tracking and continued input from the driver is required to keep the vehicle in a straight line. To correct this problem and restore the caster angle that has been lost with the suspension lift, the king-pins have to be rotated back to where they were, either by rotating the swivel housings, which is done by slotting the bolt holes, or rotating the entire axle by means of eccentric bushes or modified radius arms. To rotate the axle further forward would result in more negative caster angle, rather than restoring positive caster.

There you go. I understood further rotation of the axle was required to bring the prop shaft to the original angle ie the rotation caused by the lift wasn't sufficient. I'm confused again about how rotating back the other way helps with UJ vibration.

The impact on steering geometry makes sense.

Originally Posted by rar110

I'm confused again about how rotating back the other way helps with UJ vibration.

The impact on steering geometry makes sense.

Yeah I don't think it would, but I'm prepared to be corrected.

Originally Posted by nedflanders

Went to a driveshaft place today and explained what was happening, they said basically if the vibration is there all the time it would probably be the UJ's at too much of an angle, if the vibration is only at a certain speed it's more likely the sliding joint is nearing the end of it's travel. I can either fit a spacer or as I've got a spare prop that's too long I can have that shortened to the length I want.

I'm convinced it is a prop issue as the vibration disappeared when I ran it without the prop.

Again I'm prepared to be corrected, but I wouldn't have thought that lifting the suspension would affect the sliding joint? Again, due to the position of the gearbox-end UJ in relation to the radius arm-to-chassis pivot point.
It seems to be fairly well established that lifting these vehicles can cause vibration due to the increase in angle at the rear UJ and that a double-cardan shaft is the best fix. Have you looked at the sliding joint to see whether it is in fact over-extended? I would have thought that the money you will spend to have your spare shaft modified might be better put toward a Tom Woods double-cardan shaft. That's what I've decided to do when I lift my 130 this year.
Tom Woods' website is quite informative on this stuff.

Originally Posted by POD

Again I'm prepared to be corrected, but I wouldn't have thought that lifting the suspension would affect the sliding joint? Again, due to the position of the gearbox-end UJ in relation to the radius arm-to-chassis pivot point.
It seems to be fairly well established that lifting these vehicles can cause vibration due to the increase in angle at the rear UJ and that a double-cardan shaft is the best fix. Have you looked at the sliding joint to see whether it is in fact over-extended? I would have thought that the money you will spend to have your spare shaft modified might be better put toward a Tom Woods double-cardan shaft. That's what I've decided to do when I lift my 130 this year.
Tom Woods' website is quite informative on this stuff.

The pivot point of the radius arms is a little different to that of the transfer case/front prop - consequently the prop will need to lengthen/shorten as the diff moves up/down. From memory, the prop lengthens as the diff drops, so a lift will extend the sliding joint which may then have too little overlap (though I doubt this would be an issue with a moderate lift).

I reckon it's the rear uni - an I issue I solved in my 09 110 with a TW shaft (which has proven reliable to date).

I concur with POD and n plus one.

nedflanders, the driveline place gave good advice, except for what they said about the extension of the driveshaft. Do not fit a spacer, or change the overall length of your driveshaft.

I have no doubt that the vibration after the lift was caused by the increased operating angle of the universal joint at the transfer case end of the front driveshaft. This is common with rovers, however some are OK and some are bad (both these are subjective).

It could be that you have a little wear in the uni joints, and your flange bolts may not have been tight enough and the change in angle has been enough to cause the vibration.

Changing to a driveshaft with a double cardan joint at the transfer case is often the only solution that works well with a rover. You could try a front driveshaft from a disco II, but they weren't originally fitted with greaseable joints so it would pay to fit new uni's. They us a different flange at the transfer case, so that is another item you would need.

I had a look at my front axle last night and it has been rotated the way I thought was correct, with castor correction bushes, ie with the pinion pointing more toward the gearbox.

This was done a few years ago after vibration from taller springs. It seemed to fix the problem of vibration. But I think I also had UJs done at the same time. So that may have been the fix. I later fitted standard height springs again as the kids had trouble getting in & out of the 110.

Maybe I should swap a new set of standard bushes back in. The current bushes are probably flogged anyway.

Cheers for all the advice, going to try a new prop I had lying around first, the uni's feel alot tighter being new. it's getting shortened as it's too long so will know by friday, the prop was off a military Landie so has heavy duty unis anyway.

All these answer are regarding a lifted defa but mine is still stock standard with the same problem. So should I start looking at the front tail shaft for the vibration thanks