Thread: Still chasing vibration!!

Originally Posted by nedflanders

Still got a weird vibration from the front prop at 65kph after a 2" lift. If I fitted 3deg off set arms would this put the front UJ back in line, also would off set bushes do the same job (cheaper to buy and ship!) if I have to go the Disco prop route what fits? A D1 or D2 with flange? Cheers

There's been a bit if discussion about this lately, but my understanding is that castor correction (except when done at the swivels) will make it harder on your front shaft.

A DC prop is likely what you need ( assuming we're talking a lift-related issue).

Prop vibration is usually due to an excessive operating angle at the universal joints, and or unequal operating angles.

When Land Rover changed from leaf to coil springs they raised the front of the engine up to increase the travel of the front suspension.

This automatically created unequal operating angle, and will always be so. When they changed to the Puma engine, they raised the front of the engine further, creating an even worse operating angle for the universal at the front of the transfer case.

This is the bane of those who want to install a suspension lift in a Defender with the Puma engine. For some unknown reason, some are worse than others.

In a Rover, you will never ever equalise the operating angles of the universal joints no matter what you do with the radius arms or bushes.

Castor correction arms or bushes will however increase, not decrease the operating angle of the universals, particularly at the transfer case end, making the situation worse.

There are no cheap or easy fixes for the steering and vibration issues resulting from more than a moderate lift in Land Rovers.

slotting the swivels bolt holes is the only way to rotate the diff to get a better angle, or I ended up fitting a Cornay jointed front prop after several Disco 2 DC shaft failures - the DC is not very strong in these. Many other overseas sourced DC shafts available but some of these have reported issues too. Effectively the DC halves the operating angle - others will be able to explain the geometry of how this works. Castor correction bushes made mine worse as would corrected radius arms as explained by others. Good luck!

Mines not a Puma but a TD5, and I went for a 2" lift nothing even considered moderate. Do corrected arms raise or lower the diff pinion? I can't for the life of me understand how slotting the swivels alters the diff orientation, fine it gets the castor back but only off set arms or bushes is going to rotate the Diff. From what I'm guessing the rear of the diff needs to be raised to correct the loss of castor after the lift and straighten the front prop front UJ.

Originally Posted by nedflanders

Mines not a Puma but a TD5, and I went for a 2" lift nothing even considered moderate. Do corrected arms raise or lower the diff pinion? I can't for the life of me understand how slotting the swivels alters the diff orientation, fine it gets the castor back but only off set arms or bushes is going to rotate the Diff. From what I'm guessing the rear of the diff needs to be raised to correct the loss of castor after the lift and straighten the front prop front UJ.

They rotate the diff pinion, effectively lowering it.

TD5s suffer the same front prop issue as Pimas, though to a lesser degree.

Slotting the swivels doesn't rotate the diff, that's the whole point - correcting castor via other means rotates the diff making the pinion lower ;as above) and makes things even worse for your front prop. Slot the swivels and you'll only have the issues you're having now, not even worse issues!

In summary, you have an issue that can only be corrected with a DC, every castor correction option will either a): making things worse (bushes/arms) or b): not make things worse (swivels).

Originally Posted by nedflanders

Mines not a Puma but a TD5, and I went for a 2" lift nothing even considered moderate. Do corrected arms raise or lower the diff pinion? I can't for the life of me understand how slotting the swivels alters the diff orientation, fine it gets the castor back but only off set arms or bushes is going to rotate the Diff. From what I'm guessing the rear of the diff needs to be raised to correct the loss of castor after the lift and straighten the front prop front UJ.

yep nedflanders you're right - poor old memory letting me down as I had 2 issues - vague and wandering steering plus vibration - the slotted swivels fixes the castor hence making steering more positive and the Cornay fixed the angularity.

This from a post by SteveG explains it well: "From the factory, they come with approx 3deg positive caster in the front suspension, but that reduces as you lift the ride height. Caster reduces approx 1deg for every half an inch lift. A couple of inches lift and you're down towards 0deg. Positive caster gives you directional stability and predictable steering. None or negative makes them twitchy when you change direction. With them being live axle, the 2 main ways to increase caster are to either fit caster correction bushes (which also changes diff pinion angles which can create other issues), or to slot the mounting holes on the swivel ball where it bolts to the axle housing. Once slotted, the swivels can be rotated (rearwards at the top) to increase caster and get it back to the factory 3deg."

Cheers for all the replies, I understand castor and the need for it, I could live with it as it is as I still get self centering and the steering isn't noticeably twitchy. My concern is prop vibration, having read lots it seems that the angles at each end need to be the same to cancel out the vibration, the diff end is a lot less angle than the t box end. To increase the angle I need in fact to lower the pinion which is what off set radius arms do, as long as the prop is phased correctly won't increasing the diff joint to match the t box joint stop the vibration?? I've seen plenty of lifts much higher that don't have issues. A DC may stop the vibration but won't bring back my castor.

Originally Posted by nedflanders

Cheers for all the replies, I understand castor and the need for it, I could live with it as it is as I still get self centering and the steering isn't noticeably twitchy. My concern is prop vibration, having read lots it seems that the angles at each end need to be the same to cancel out the vibration, the diff end is a lot less angle than the t box end. To increase the angle I need in fact to lower the pinion which is what off set radius arms do, as long as the prop is phased correctly won't increasing the diff joint to match the t box joint stop the vibration?? I've seen plenty of lifts much higher that don't have issues. A DC may stop the vibration but won't bring back my castor.

If your vibration is being caused by an excessive angle in the Uni at the T/C end (which is typically the case in lifted TD5/Puma Deefers), then increasing any of your drive line angles is unlikely to assist?

I can confirm that my 2 inch lifted Puma with a DC and castor corrected arms has no front prop vibration issues.

FYI, OME suspension guide recommends a DC be fitted when a TD5 is lifted (it's just that on many TD5s people seem to get away without one).

Hope this helps.