Vibration after changing Universal Joints

[johnyrover]

Good evening all,

I find myself in need of the brains trust. I have just finished changing all four uni joints on my p38. All went well, I made sure the new joints were nicely centred in their yokes, and the shafts went back on in the same position they came off. I used marks to ensure this.
However. Now when I approach 100kph there is a vibration that gets worse the faster I go. I took the old girl up to 130 and the vibration was more pronounced and audible. I can feel it through the steering wheel and through my seat.
Any input would be greatly appreciated.
Cheers
John

[PeterH]

Hi Jonn, I recently replaced all my uni joints due to a vibratrion very similiar to what you are describing.
While the new uni's definitely made things smoother, the vibration was still present.
I also got all 4 road wheels balanced, which also helped improve things, (this is a fairly inexpensive place to start, might be worth a shot before delving deeper).
I did a lot of reading and investigating, even took my front drive shaft in to get checked by a specialist, indeed there was a slight wobble in that shaft.
I got the shaft balanced, which was part of the problem, but the vibration was not as bad, but still present.
In the end, it turned out to be a partially seized viscous coupling.
There are a few tell tail signs...
Have you noticed any front wheel chirping during cornering?
Has your turning circle become similar to that of the Titanic?
In your case it might not be the vc, I would investigate the easy stuff first, but if it is your vc, I replaced mine myself, also did a how to with photos if you are interested in having a look:
http://www.aulro.com/afvb/p38a-range-rover/199016-p38-viscous-coupling-replacement-photos.html
Hope that is of some help.

[johnyrover]

Thanks for the reply. I had no vibration before I changed the uni's. I only changed them because I ran them dry once and they started making noise. I think my vc is ok because I can still do the lifted wheel test and my turning circle is still nice and small. Also no chirping even on smooth concrete. I also had all four tyres replaced and balanced about 6,000 k's ago. Thanks for the link all the same though. As with all cars of a certain age (1997 for mine) I'm sure its only a matter of time.
Cheers
John

[Keithy P38]

Thanks for the reply. I had no vibration before I changed the uni's. I only changed them because I ran them dry once and they started making noise. I think my vc is ok because I can still do the lifted wheel test and my turning circle is still nice and small. Also no chirping even on smooth concrete. I also had all four tyres replaced and balanced about 6,000 k's ago. Thanks for the link all the same though. As with all cars of a certain age (1997 for mine) I'm sure its only a matter of time.
Cheers
John



I experienced a similar thing with mine. Replaced the front uni's as they were worn. Turned out to be the wheel balance. I only had a balance and alignment not long prior, my P38 had thrown a weight after only 800km.


Cheers
Keithy

[Sitec]

Long shot, but did you by chance pull the prop shaft in half to check the splines when you were doing the joints? And if so, when you slid the two pieces back together, did they go back in phase? IE, the yokes and flanges have to be in the same plane at each end. If not, that's you're vibration. The other thing to check. When you fitted the new uni joints and circlips, did you then give each cap housing a belt to make sure they're seated against the circlip? This makes sure that there's equal/no resistance within each joint. If one was tight, this will also cause the vibration you describe....
If my garb about phasing does not make sense, then this will help explain it...

https://m.youtube.com/watch?v=gmV4qwLfOMY

[johnyrover]

I wont rule out the wheel balance, but it was only directly after changing the uj's that this happened. Sitec, I did not pull the splines apart, but I did give the yokes a knock. I only did this till I got free movement of the joint. I'm thinking that maybe I did not give it a hard enough wack. I'll give that a go.
Cheers
John

[Hoges]

Long shot, but did you by chance pull the prop shaft in half to check the splines when you were doing the joints? And if so, when you slid the two pieces back together, did they go back in phase? IE, the yokes and flanges have to be in the same plane at each end. If not, that's you're vibration. The other thing to check. When you fitted the new uni joints and circlips, did you then give each cap housing a belt to make sure they're seated against the circlip? This makes sure that there's equal/no resistance within each joint. If one was tight, this will also cause the vibration you describe....
If my garb about phasing does not make sense, then this will help explain it...

https://m.youtube.com/watch?v=gmV4qwLfOMY

Except for P38s!!:angel:

Sometime in the late 80s /early 90s the front axle was modified (slightly tilted) in production to increase the castor on the front wheels to improve directional stability.

This put the UJ thrust angles almost at their limit at normal driving height for vibrationless operation. Instead of fitting the front shaft with a double cardan joint to make it a true CV joint, they took the "easy" way out and changed the phasing of the shaft. Also, an "elastomeric mass" was added to absorb/counter vibration (the heavy 'discus' with the wire retainer on each axle -a similar setup is sometimes used on helicopter rotor heads).

As a result, the front drive shaft is now phased such that the flange closest to the transfer case "leads" the front diff flange (IIRC) by 2 splines in the normal direction of rotation. Later model drive shafts I've seen are actually machined to ensure correct fitment. The rear shaft is as per Sitec's post.

EDIT: When you grease the UJs immediately after fitting don't forget to force in enough grease to 'purge' the UJs so that the grease weeps freely from each arm of the UJ. This is very important.The UJ seals are designed for this to happen. Also make sure the sliding joint is well greased

[Keithy P38]

I'd best be pumping more grease through mine then :-o

[PeterH]

Just a thought, but your old uni's may have been worn and allowed just enough movement to mask a vibration from another source.
So by fitting the new uni's, the driveline is now tighter and the vibration has now become noticeable.
I hope it is just the uni's not quite seated properly.
Cheers, Pete.

[johnyrover]

I pulled the back one off and gave it a belt. Vibration still there. I didn't want to have to do the front again (bit of a pain). On the up side doing this is like being a doctor - you can never get enough practice.
Will keep you posted.
Cheers
John

[daf11e]

Just a thought, but your old uni's may have been worn and allowed just enough movement to mask a vibration from another source.
So by fitting the new uni's, the driveline is now tighter and the vibration has now become noticeable.
I hope it is just the uni's not quite seated properly.
Cheers, Pete.


As Peter says I've read a few cases where the basics were the problem ie: Tyres faulty on inside balance etc.

[johnyrover]

Thanks for input guys. Much appreciated. Got a bigger hammer to it, and no difference. Off to the tyre mob tomorrow for a wheel balance. As usual, I will let you know how it all ends.
Cheers
John

[Scouse]

Know anyone nearby with a P38?
If so, I'd be swapping shafts to try and pinpoint which one might be causing this new issue.

[davidsonsm]

This thread has me spooked. I've a set of new UJs ready for fitting sitting in the garage. Thought it was a straightforward job to fit them. Hope it proves to be. I don't have any wobbles at present. Hope I don't introduce any.

[johnyrover]

No I dont know anybody with another p38. But I have read threads about taking out the front prop shaft and driving the car. Is this an option? Could I drive at highway speeds without the front prop shaft in? The wheel balance did not make a jot of difference. Now at the risk of sounding like a P38 owner who can sometimes let their imaginations run away with them, before I replaced the joints, I thought I detected a slight vibration when sitting in the rear seat. It was so slight that I put it down to road rumble. Rear wheel bearing? (I am purposely not entertaining the vc at this stage) :)
Cheers
John

[bee utey]

You can drive a P38 without a front shaft but whatever you do take off gently to not overload the viscous coupling. At road speed it'll be fine.

[mtb_gary]

No I dont know anybody with another p38. But I have read threads about taking out the front prop shaft and driving the car. Is this an option? Could I drive at highway speeds without the front prop shaft in? The wheel balance did not make a jot of difference. Now at the risk of sounding like a P38 owner who can sometimes let their imaginations run away with them, before I replaced the joints, I thought I detected a slight vibration when sitting in the rear seat. It was so slight that I put it down to road rumble. Rear wheel bearing? (I am purposely not entertaining the vc at this stage) :)
Cheers
John

John

As bee utey said no problem without the front prop shaft....I've driven without it myself.

Gary

[johnyrover]

Thanks guys. Im going to have to live with it for a bit. But soon as i get back on the job again i'll let you know what happens.
Cheers
John

[PeterH]

Something else you could check, if you raise the front of the vehicle so the road wheels are off the ground to take all tension off the drive shaft, then get a hold of the diff yoke and give it a push and pull from side to side, up and down, look for any movement which could indicate a worn bearing.
Same on the transfer case end of the front drive shaft.
Repeat for the rear of the vehicle.
If you find any movement at any of those points you may well have found the culprit.
I replaced my front diff center after discovering quite a bit of movement using this method, one of the bearings was on the way out. I also replaced the output bearing on the transfer case end after discovering movement there too.
Cheers, Pete.

[johnyrover]

Hi Guys.

Here is the situation so far.

Removed front prop shaft - vibration still present but diff whine gone, gone, gone. Also there may be something going on with the VC, as there was a very slight shudder during tight turns - now smooth. Thought that was normal.

Rotated rear prop shaft 180 degrees on the diff pinion - vibration reduced to the point that I cant tell if its road rumble. I can live with that. :)

I have a question. How long can I leave the front prop shaft off without detriment to the car? Does it need to be there at all? I don't want to spend the money on a diff that I don't use off road, and I am really enjoying the peace and quiet.

Cheers
John

[PeterH]

As long as you take it easy with acceleration, you should be fine to drive it without the front shaft connected.
It will however make the steering feel different as it is now a rear wheel drive only, it may tend to wander a bit and feel lighter. Be careful of oversteering, particularly at speed.
It will place alot of strain on your vc, but if yours is on the way out anyway, it doesn't really matter. Having said that, if you do decide to replace the front shaft in the future, you will need to do the vc as well.
I drove mine from Melbourne to Shepparton with no front shaft (roughly 400 km) return drive in one day with no problems at all other than what I have already mentioned.
I have read stories of people driving with no front shaft for an extended period of time with no problems.
When I put in a new vc on mine and refitted the front shaft, it felt much better to drive, much more solid and stable compared to no front shaft.
The reason the diff whine is gone is probably the vc partially seized, causing transmission wind up and strain on the diff. Removing the shaft has taken the strain off the diff.

[johnyrover]

Well I erred on the side of caution and put the front shaft back in. I didn't like the light feeling in the the steering wheel, and if there is any life left in the VC I don't want to risk shagging it completely. From what I've read my VC might be a bit stiff but its been the same since I got the car two years ago and the diff is no louder either. It definately feels better with it in. The little vibration from the back will have to be fixed -I cant live with it :-). But I've gotten so good at taking the bloody shafts off that it wont be a big hassle.
Once again a big thank you to you all for your help.
Till next time.
Cheers
John