Front propshaft vibration

[eeyore]

Looks like my ute has recently developed the classic front propshaft vibration at around 60km/hr & 80km/hr that is usually associated with lifted Pumas (?), perhaps in celebration of it's 600k birthday

Attachment 131967

Front propshaft has brand new unijoints, and there is no noticeable play in the slip joint or at the diff pinion or gearbox output shaft. The vibration occurs both accelerating / decelerating and at a steady speed. Remove the propshaft and it vanishes.

The ute is a 120" Isuzu with a PTO winch, and the only change to it recently is the exchange of a fibreglass canopy & ply floor / aluminium tray / rubber mat for a timber tray and Trayon camper, plus the removal of a 120l undertray fuel tank. My initial though is that extra weight is causing the rear suspension to sag, lifting the front to an angle that puts the front UJs under stress (its also recently developed a bit of steering wobble). However, I took it over the local weighbridge today is about 2250kg with driver / full fuel tank / trayon, similar to what it was before. It does have a slight 'nose up' attitude (!) - but again, not new - and an appetite for front UJs (thought that was me not keeping up enough grease to them..).

Here's a couple of pics. As you can see, sag is pretty minimal.

Attachment 131973IMG_1473.jpg

The suspension set up is King Springs front KRRR02 (measured installed length @ 295mm) & rear KLRR05 (@ 340mm). From what I can work out, this is about 35mm (front) & 40mm (rear) higher than a stock 110. So I guess I have a couple of questions for the brains trust.

1. Do people think that the combination of the lift plus (slightly) more rear sag is enough to cause the propshaft vibration problems?

2. If the above is true, will it be enough to replace the rear springs with higher rated ones (KLRR05HD) or higher rated + longer (KLRR05EHD), or even go with air bags (helpers or coil replacements) - ie reduce the rear sag? From the regular 400kg load it carries and when at touring weight (another 400kg +) it should have KLRR05HDs at least. Alternatively I could put shorter springs on the front, perhaps add helper bags to the current rears. I'm a bit reluctant to go down this route though, since the pto is a bit of plough already.

3. Or am I completely barking up the wrong tree? Could the propshaft be out of balance or something?

Cheers
Simon

[Ancient Mariner]

Out of phase ?

AM

[clive22]

Perhaps find a try someone else's propshaft. If it goes it must be something with your prop shaft.

I know my slip joint was just slightly worn and this was enough to induce a vibration. New slip joint problem gone.
Even just a little bit of freeplay - like a tiny little click may be enough.


But if the vibration is still present, then surely a double carden would be in order. To my mind a prop-shaft must be able to accommodate the arc of suspension travel, limiting the arc is solving the problem backwards.

Clive

[eeyore]

Out of phase ?

AM

I did wonder about that. It hasn't been apart recently but I think it has in the past. I'll look into that. Thanks for the suggestion.

[eeyore]

Perhaps find a try someone else's propshaft. If it goes it must be something with your prop shaft.

I know my slip joint was just slightly worn and this was enough to induce a vibration. New slip joint problem gone.
Even just a little bit of freeplay - like a tiny little click may be enough.


But if the vibration is still present, then surely a double carden would be in order. To my mind a prop-shaft must be able to accommodate the arc of suspension travel, limiting the arc is solving the problem backwards.

Clive

I guess I focused on the weight / suspension as the source of the problem as the vibration appeared around the same time but I might be exaggerating its effect, especially since the measured compressed lengths suggest they probably sitting around the correct height. I'll investigate the propshaft a bit further. A double carden would definitely be the best solution but if I can get away with the "good-enough but a lot cheaper" option, I'll probably take that at the moment. Thanks for your advice Clive.

[rick130]

Out of phase ?

AM

Ditto, or actually it should be out of phase to stop the dreaded vibes

[mox]

If propshaft has vibrations it did not have before, have a look at it to check the alignment of the front and rear uni. joints. Remember the Hardy Spicer type universal joint is NOT a constant velocity joint. Farmers who use tractor power takeoffs are usually well aware of this but many others aren't. When there is an angle between the driving and intermediate shafts, as they turn the intermediate shaft is alternately accelerating and decelerating. So for the driven shaft to run smoothly, the second uni needs to cancel out irregularities created by the first one. To achieve this, the yokes on the intermediate shaft need to be in line.

Some shafts with slip joints on the intermediate shaft are set up so that if they are pulled out, can only be put back in the correct place. However LR propshafts have 16 splines. There are two right ways they can be put in and 14 wrong ones. Then of the two right ways, check which one allows both grease nipples to be accessed from the same side.

However, on Defenders there is an inherent problem with the front tailshaft which seems to cause some vibrations. The angles the uni joints run at are not the same, with the rear one on the transfer box end running at an angle while the one on the diff end is nearly straight. A crude remedy which LR uses which seems to reduce the problem is to run the front and rear halves of the intermediate shaft 45 degrees out of phase.

Whoever replaced your uni joints almost certainly would have separated the two halves of the intermediate shaft to make this distasteful job less difficult. Then most likely pushed them back together wrong. With the intermediate shaft yokes lining up which is correct in normal applications, 22.5 degrees out of phase or 45 degrees out of phase which seems the best for these particular Landy front propshafts, should not be much problem. However, I suspect yours is 67.5 or 90 degrees out of phase. Note with the latter in normal applications where the unijoints run at about the same angles, the second one is creating the same irregularity again as the first one - ie doubling it rather than cancelling it out. When driving and driven shaft are in line usually no problem. When they are not, it is usually very noticeable.

If my diagnosis of your problem is correct, you need to unbolt the propshaft, pull it apart at the slipjoint and push it back in a more appropriate alignment than it was.

[eeyore]

Thanks for the reply mox. I checked my front propshaft and it was set out of phase - not sure at what exactly but less than 90 degrees. Prior to your post , I'd looked on the web but couldn't find any consensus on precisely what degrees, or number of splines, out of phase it should be. So I used this diagram as a guide:

D1propshaft-phasing.jpg

where A is the transfer case end. Took the propshaft out, rotated the slip joint one spline out of phase (22.5 degrees), tried it, still vibration. Repeated exercise at two splines out of phase (45 degrees), same result. Not sure about the alignment of the grease nipples. From your description of "two right out of 16" I take it doesn't matter whether one end is rotated clockwise or counter-clockwise with respect to the other?

Another thought: should the propshaft yokes at the transfercase's rear and front output shafts be in phase? That's something I've not thought to check and it's quite possible that somewhere along the line of replacing unijoints the alignment marks for reassembly have been mistaken / missed...

[mox]

The diagram you have posted shows what is generally regarded as the "correct" misalignment for D1 and Defender front propshafts, which are the same part and interchangeable if you need a spare. In the diagram, angle A is 180 degrees and angle B 135 degrees. 45 degrees out of phase. Note that whatever the position, if you pull the shafts apart, turn one 180 degrees and push them back together, the way the universals behave will be the same. Those having to grease them would generally regard it as more convenient to having them set up so both grease nipples are accessible at the same time rather than having to turn shaft something like 180 degrees to get at the other one.

The transfer box rear and front output shafts in the full time 4wd type transfer box would only be locked in the same alignment when the centre differential is locked. The alignment - wherever it happens to be locked does not matter because vibration in one propshaft should have no effect on vibration or otherwise of the other. When the centre differential is unlocked, as it should be for most types of driving, the diff can function and at times the front and back shafts do not run at the same speeds. eg. A Disco here owned by someone else presently has fairly new tyres on the front and worn ones on the back. In this case, effective size of tyres regarding vehicle speed would be the average of the four fitted. The rear output shaft would be turning slightly faster than the centre diff carries and the front one slightly slower. Then while going around a corner, the rear wheels tracks take a shorter path than the front ones so the rear tailshaft turns slightly slower than front one.

If your vibration problem is not caused by alignment of yokes on intermediate shaft being 67.5 or 90 degrees out of phase - ie compared with having the two yokes on the intermediate shaft lining up, maybe problem becoming apparent after unijoints replaced is that in the process, a balance weight has come off. The long 'half" of the intermediate shaft is a tube with a female spline in it. Near each end on the outside of each tube is a something like square piece of metal measuring the the order of 25 mm each way and 1 mm thick. Presumably "spot" welded with low voltage high amperage electric current. Probably some inadequately fused ones fall off at times, causing shaft vibration. On every shaft they would be different sizes and in different alignments on each end. To balance them properly, need to be put on appropriate dynamic balancing machine at specialised propshaft repair business. Among jobs they can do is straighten and rebalance some bent shafts. eg I saw a case around 20 years ago of $150 to repair a rear Defender 130 propshaft after an idiot picking up accident damaged vehicle with a forklift did more damage.

Just looked at three Disco 1 / Defender front propshafts presently handy here. Weights all in different positions. If one has fallen off, most likely fairly obvious where it was unless after unijoints were replaced, shaft was repainted.

Probably something to check is possibility of a very rough installation job. Are all the circlips holding bearing caps in the yokes in place? Can happen that the odd needle roller falls down into bottom of cap. Then when opposite cap is installed, it will not go right in. Then if rough mechanic left it as is rather than pull apart and fix, would be out of balance. I have found that a good way to virtually stop needles falling out during installation is remove caps and smear plenty of the likes of Nulon or Wynn's red grease in them. Is sticky. Also found it lasts better than other greases in tractor PTO unis that are heavily loaded for their sizes. While at it and bearing caps are off yokes, reckon a good idea to pump some of same grease through nipple. Make sure clean grease flows out everywhere it should. Have seen old grease set like cheese. When greasing first time it may not necessarily go readily into all 4 caps. Just keep going through points of least resistance. Seems probably a major cause of premature unijoint failure is one of the bearings getting little or no grease while it readily comes out of seals of others.

Maybe next step for you is try to "pinch a loan" or whatever of another apparently good propshaft and try it on your vehicle for vibration test.

[eeyore]

Thanks for another useful reply mox. I appreciate your help on this.

I pretty thoroughly checked over the unijoints when I pulled the propshaft. All the circlips are in place, movement is smooth in all directions and there is no slop at all. I also remember seeing a couple of balance weights on one end of the shaft but I did not consciously check for evidence of missing ones. I'll do that next. Failing that as the cause, I'll do as you and others have suggested and see if I can find another shaft to swap with.

Cheers
Simon