Front drive shaft alignment.

[PeterH]

I recently replaced my front uni joint.
Following the rave instructions I marked shaft alignment points before disasembling, but during the replacement everything got covered in grease and I lost the marks.
I put it back together but am experiencing a slight vibration while driving, which feels very much like a drive line vibration. While it's not bad, it is a bit annoying.
I am going to replace the other uni joints to rule them out as they are probably quite old, so while I have it apart again, is there any way to tell the proper front shaft alignment?
I saw a punch mark on the main shaft, but nothing obvious on the small part to line it up with.
I had a look on Rave and also did a search but found nothing on this for P38's.
I read some Land Rovers have the front shaft deliberately a bit out of phase, not sure if that is the case with P38's though.
Can anyone help with this?
Cheers, Pete.

[Hoges]

Hi Peter,
as best I can determine, the front shaft is arranged such that its rear UJ (closest to the T/F case) "leads" the front UJ by 2 splines, with the sliding joint closest to the transfer case...
This is illustrated in the early edition of RAVE dealing with the RR "Classic" but I couldn't find it repeated in the later RAVE editions for the P38, though it is my understanding the front end alignment is the same for both vehicles. Apparently in the later Classics they pitched the front axle 12 degrees to improve straight line stability and in so doing compensated for the altered UJ thrust angles by changing the UJ phasing as described as well as bolting the elastomeric mass to the front and rear axles to counter the ensuing vibration.... a double cardan shaft is probably the only means of truly eliminating the vibration.

cheers

[PeterH]

Thanks for that info Hoges, I can work with that!
Will give it a go over the weekend.
I know the vibration might be a worn uni joint, but will be good to know the shaft is set properly.
Cheers, Pete.

[TheTree]

Hi

If you are sure the Uni Joints are all cool, you can have the tailshaft dynamically balanced if it still vibrates

Steve

[TheTree]

HI

Also of course, any slight wear in the splines can cause vibration.

I have never had an issue with tailshaft vibration on any rover i have owned, it should not vibrate at all :eek:

Steve

[PeterH]

Thanks Steve, I'm going to replace the other front uni joint to eliminate that from the list, while I have it apart I'll line up the drive shaft and see how it is from there.
Failing that I'll do the rear uni's as well, may have to get the raod wheels balanced incase I've lost a weight off a rim.
Failing that I'll be looking at getting the shaft looked at.
Cheers, Pete.

[Hoges]

Complete "how to" track vibration... Prop-Shaft Phase (http://www.csse.monash.edu.au/~lloyd/tildeLand-Rover/LRO/prop.phase.html)

cheers

[peter51]

Ive just had my 2000 p38 front propshaft overhauled and balanced.
When I got it back to my shed for fitting it wouldnt slide in and out. So back to the gearbox shop I went knowing they had put it together incorrectly. The for aft part - hookes joint I think- key in only one way. If you look inside the female side you will see a machined out spline. This ensures it can only go together one way.
So I insisted that I inspect the splines for damage when they got it apart - It was stuck pretty hard. I inspectd the splines. carefully and luckily no damage, eventhough they had forced it together.
Interestingly the senior man turned up to take control and said that because it had been miss splined it would need a rebalance now that it was put together correctly.

However they spray painted over my witness marks which I made on removing from the car - eventhough I said do not spray over these marks.

So make sure it is splined correctly on reassembly, cause even the specialists get it wrong.
Also make sure the hookes joint - sliding bit- goes against the transfer case on refitment - you probably know that already.

[PeterH]

Interesting peter51, I did notice the inside of the spline did have a gap instead of one of the splines.
Are you saying it only goes together one way? If so, that would make a lot of sense, as it would be all too easy to assemble the wrong way, as I could not see any marks to line anything up with.
It was hard trying to refit the shaft from underneath, I noticed it would not go on until I rotated the shaft around, then it would slide on ok. So maybe the shaft is on the correct way and the other uni joint is the culprit.
I may have to take the shaft back off, will be easier to see when not laying under the car.

[peter51]

yes it only goes together one way in order to maintain the phasing. I cant tell u if my vibration has been solved because I have a coolant leak and cannot test drive the vehicle untill I get a new o ring.

Any minor slop in the uni will cause the prop shaft yokes to not follow their correct longitudinal axis - for want of a better description the yoke is thrown eccentrically each revolution.

[PeterH]

Thanks peter51, hope you get that o ring sorted.
Yes even slight uni slop causing vibration makes sense, I'm going to do all my unis, as they have been on there since before I owned the car, no telling how old they are.

[hhiemstra]

so, how did this turn out??? I've just replaced all my uni joints (one of mine seized) and ever since its had a vibration between 50-60km/h and 100+km/h. I've had the front shaft off it seems like a million times... Why oh why land rover did you not specify these details in the rave manual??? any one have some pics of an un touched unit?

[PeterH]

I'm finally getting around to replacing all the unis this week.
I did the front one a couple of months back, as it had a lot of play and was urgent.
I still have a slight vibration over 70kmh, which does get a bit worse approaching 100kmh.
So as a process of elimination, I have put new tyres all round, as they were all on the way out, as well as balancing all wheels.
While that did improve things, it still vibrates as described.
So the next step, replace all the unis and see what that does.
I'll be doing that job on Wed or Thurs this week, will post my findings then.

[hhiemstra]

so I crawled under my hateful piece of ... and found that one of my new uni joints is shagged... ARGH!!! gotta replace it again. Can any one tell me when looking at the front shaft with the transfer case end closest to your face and the diff end furthest away, should the transfer case flange be clock wise or anti clockwise in comparison to the diff end?

[Hoges]

so I crawled under my hateful piece of ... and found that one of my new uni joints is shagged... ARGH!!! gotta replace it again. Can any one tell me when looking at the front shaft with the transfer case end closest to your face and the diff end furthest away, should the transfer case flange be clock wise or anti clockwise in comparison to the diff end?

uhmm... not sure what you're asking...

[PeterH]

hhiemstra, is it the very front uni that has been damaged?
I recently did my front one, which was chewed out, only to find the vibration returned shortly after replacing it.
When I had a close look, my new uni joint was fine, but I had not seated the circlips on the joint in quite enough, so after driving for a bit, it was able to work itself a bit loose again.
I took it apart again and made sure the sirclips were well and truly seated in the grooves properly.
It seems to be fine now, but I will be replacing all my unis for good measure in the next day or two.
I have read a dodgy uni joint can effect the uni joint on the other end of the shaft due to all the vibration, so I'd be looking at replacing at least the two on the affected shaft if you are experiencing problems.
As far as shaft alignment goes, to the best of my knowledge it only goes on one way, the reason you mark the shaft on disassembly is to make it easy to locate the shaft when refitting.
I lost the marks on mine and found I could only slide the shaft partly on before it started to jam, so I carefully rotated the shaft until it slid straight on with no resistance.
Probably a much easier job when it's up on a hoist, as opposed to on your back under the car...they are the times I wish I had a hoist!

[hhiemstra]

my tc one is shagged, if i recall correctly thats the one that seized originally... now I think I need to replace the tc output bearing...

the shafts will go together any way, the splines are equally spaced, altho there is one missing on the female side, but that doesnt stop them being mated incorrectly... just needs more encouraging...

[hhiemstra]

Hoges - what I mean is, say you have the front drive shaft out, standing up next to you, transfer cas uj in hand, diff uj on the ground between yr feet... which way is the uj in yr hand turned compared to the uj between yr feet?

[Hoges]

Hoges - what I mean is, say you have the front drive shaft out, standing up next to you, transfer cas uj in hand, diff uj on the ground between yr feet... which way is the uj in yr hand turned compared to the uj between yr feet?

ah ha! see post #2 of this thread ;):D
cheers

[hhiemstra]

OK, I just purchased a new front output shaft bearing (thanks brit part). Had to remove the gearbox cross member... anyways, new bearing installed, we shall see if that fixes the vibrations...