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Trevor Pickering
Frequent User
Username: commander1

Post Number: 76
Registered: 6-2012
Posted on Saturday, 27 October, 2018 - 19:43:   Edit PostDelete PostView Post/Check IP

I am having issues with the prop shaft in my SC3.
The Detroit coupling was worn so I had it replaced with a normal UJ on a sliding shaft.
The other UJ's have been replaced as well and also the centre bearing and the whole set up balanced by a specialist company.
I am still getting some vibration and the centre bearing seems to be the culprit even though it is new!!
All engine mounts are new and tight and I have rebuilt the rear axle at vast expense and this is smooth and quiet.
I have tried re alighnment of the shaft several times but still getting the problem.
I spoke to a company who rebuilds the auto boxes and they said that they do a conversion to a fixed type centre bearing and this will solve the problem
Does any one have a view on this please?

Thanks

Trevor
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Christian S. Hansen
Grand Master
Username: enquiring_mind

Post Number: 954
Registered: 4-2015
Posted on Saturday, 27 October, 2018 - 20:33:   Edit PostDelete PostView Post/Check IP

Trevor...
These days the number of times "broken or defective right out of the box" rears its head is relevant. If the bearing seems to be the culprit discount that it was recently replaced and pursue to eliminate it as the problem. There was similar issue in another thread with rear Shadow rams as I recall. New, yes. Defective, also yes.

.
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Trevor Pickering
Frequent User
Username: commander1

Post Number: 77
Registered: 6-2012
Posted on Saturday, 27 October, 2018 - 21:40:   Edit PostDelete PostView Post/Check IP

Thanks Christian
This is the second "new" bearing I have tried with the same result but they are from the same source!
If you spin them up by hand they seem fine but on the car under some load there is noise(clicking)that can be detected.
I will try another from a different supplier and see if that makes a difference.
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Paul Yorke
Grand Master
Username: paul_yorke

Post Number: 2079
Registered: 6-2006
Posted on Saturday, 27 October, 2018 - 22:51:   Edit PostDelete PostView Post/Check IP

There are some phone apps which measure vibration and graph it. Hold it against different areas to help locate strongest measurements. I have found it helpful in the past.
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Mark Aldridge
Grand Master
Username: mark_aldridge

Post Number: 570
Registered: 10-2008
Posted on Sunday, 28 October, 2018 - 03:37:   Edit PostDelete PostView Post/Check IP

Trevor, if the bearing is standard, try a local bearing factor for a well respected make. I fitted some MG front wheelbearings recently from a MG parts supplier, and they are infinitely worse than the worn originals ! Will take them to our local bearing supplier and replace again with quality units.
Mark
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Martin Webster
New User
Username: martin_webster

Post Number: 3
Registered: 9-2018
Posted on Sunday, 28 October, 2018 - 08:21:   Edit PostDelete PostView Post/Check IP

Trevor, have you checked the springs on the centre bearing support bracket for tension and integrity. This may be causing the vibration. My Cloud II suffered from a similar problem and after the old springs were replaced, the vibration was eliminated.
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David Gore
Moderator
Username: david_gore

Post Number: 3033
Registered: 4-2003
Posted on Sunday, 28 October, 2018 - 09:15:   Edit PostDelete PostView Post/Check IP

If possible, check where the bearings were made, I would not be surprised if a large percentage of new bearings are being sourced from low-wage countries where Quality Control is of a low standard or missing completely.

I would be looking for bearings actually made [not repackaged] in the USA, Japan or Europe to have the best chance of getting an item made to a specification rather than price.
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Trevor Pickering
Frequent User
Username: commander1

Post Number: 78
Registered: 6-2012
Posted on Sunday, 28 October, 2018 - 21:30:   Edit PostDelete PostView Post/Check IP

Thank you for your help
The bearings I was supplied with are SKF with metal shields.
The original bearing is a Hoffman with NO shields and is loaded with grease on installation and is sealed by a large sealing "washer" with an O ring.
I am now of the opinion that the metal shields on the new bearing may be part of the problem as they have been rubbing slightly on the inside of the sealing washer.
The sealing washer is held against the bearing by a large spring that is compressed when the drive flange is fitted.
I am going to try a FAG bearing with rubber shields.
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Trevor Pickering
Frequent User
Username: commander1

Post Number: 79
Registered: 6-2012
Posted on Sunday, 28 October, 2018 - 21:35:   Edit PostDelete PostView Post/Check IP

Paul
Thanks for the suggestion of the vibration app for the phone.
I will give that a try.
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christopher carnley
Unregistered guest
Posted From: 109.148.48.251
Posted on Sunday, 28 October, 2018 - 21:35:   Edit PostDelete PostView Post/Check IP

If the bearing is the grease packed and sealed type, then I would not blame the bearing.

If the suggestion of Martin does,nt work, then check the load on the friction washers.

It is a mistake to substitute a U.J for a C.V joint, ie the Detroit ball and trunnion coupling and you may have induced a resonance from the acceleration/deceleration forces within the front UJ spider into the central UJ, or between the front UJ and the pinion flange drive UJ.

Some time ago P&A Wood created a front section with a modern CV joint as a substitute for the ball and trunnion Detroit type.


(Message approved by david_gore)
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Trevor Pickering
Frequent User
Username: commander1

Post Number: 80
Registered: 6-2012
Posted on Monday, 29 October, 2018 - 21:31:   Edit PostDelete PostView Post/Check IP

Thanks Chris
The bearing is the sealed type and after careful checking by hand there is a rough spot!!!This is a new SKF bearing but it is possible that it may be a cheap "copy".
I have rebuilt all the friction washer system and set the bolts to the correct torque 60ft/lbs as per the manual.
Both springs are good as well.(thanks Martin)
I know of other Cloud owners who have done this modification on the front shaft with no problems.
I have ordered a new FAG sealed bearing and will try this.
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Trevor Pickering
Frequent User
Username: commander1

Post Number: 83
Registered: 6-2012
Posted on Thursday, 22 November, 2018 - 20:41:   Edit PostDelete PostView Post/Check IP

Problem Solved!!!!

Changed the bearing for a FAG new one and no more vibration.
I am sending the other one back to the supplier for a refund
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Larry Kavanagh
Prolific User
Username: shadow_11

Post Number: 267
Registered: 5-2016
Posted on Friday, 23 November, 2018 - 05:29:   Edit PostDelete PostView Post/Check IP

Great result, happy motoring.
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David Balfour
Prolific User
Username: sidchrome

Post Number: 146
Registered: 2-2009
Posted on Monday, 04 March, 2019 - 15:16:   Edit PostDelete PostView Post/Check IP

My SCII has a long chequered history of issues. I have finally got the brakes functional again and now that the rear dampers work, and will probably be left on H since that setting is great on Australian roads, I want to start driving the car regularly for the first time since owning it. I have an issue with driveline shudder. The gearbox has been rebuilt less then 100 miles ago, and the trans guy thinks the shudder is the drive shaft- maybe. Maybe he is right! If it was the trans, you would only expect vibration under load, but I get a lot under load. I think I have some all the time, but it is so hard to tell. One of the springs was missing from the centre bearing support, so I jury rigged another for the moment with what may be similar tension until I can procure a replacement. Everything else I have pulled apart so far has been completely stuffed, so I don't see why the Detroit coupling or UJs should be immune from issues. It's starting to wear me down. I have had the car for 10 years and never had it running correctly in all this time. in fact I've only had it running for 18 months and only done about 100 miles in total due to the brake problem- overhauled master cylinder by professional was sent for sleeving. Got it back not sleeved - leaked after a week. Took me 16 months to remove again. Sent to the "Guru" instead. Came back, installed, the small one would not prime. Removed for a third time - stainless sleeve too long thus sealing the HP seal in front of the check valve. Fluid could not get past. I did the rear dampers myself and replaced the conventional seal with a lip seal after polishing out all the pitting. Having repaired the steering, the dampers, the brakes, and paying someone to do the transmission at a princely sum, I'm losing the will to attend the May Federal Rally 100 miles away. Some positive encouragement right now would help. I certainly don't miss lyng on the garage floor with a face full of brake fluid.
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Norman Geeson
Unregistered guest
Posted From: 81.99.138.38
Posted on Monday, 04 March, 2019 - 21:23:   Edit PostDelete PostView Post/Check IP

David

Re-Drive shaft vibrations S type
A few suggestions that may be worth checking out to cure your vibration.

I am aware of the vibration problems originating from the drive shaft floating centre bearing and the front joint on S type cars. There was (and still is) an inherent vibration problem in the drive line of these post war cars. The company were aware of a problem existing and damped it out by utilising the front Detroit joint.

Unfortunately if components are worn or the centre bearing is not “floating” correctly the original vibration returns. If the centre bearing springs are not correct you are likely to face problems.
However, if the problem is cause by a worn Detroit joint the vibration usually (but not always) appears about 57 mph. It is possible to replace the Detroit joint with an “end floating “(cannot remember the name) constant velocity joint, and drive shaft specialists should be able to do this fairly cheaply. It is important that the joint will accept end float under load of up to about 4 or 5 mm.

Check the axle pinion bearings for wear by repeatedly shaking the rear drive shaft joint up and down. You should expect, and witness no movement. Eventually the main axle bearings will gall and wear such that the crown wheel will tilt, under drive and overrun conditions, this shows up as axle noise and can usually be recognised as such. If in doubt remove the rear seat and listen with a scope while someone drives the car. Don’t attempt to drive one of these cars with any axle noise, it makes for a very, very, very expensive game.

Examine very carefully the REAR drive shaft joint. Look for the drive shaft and axle flange not seating together, it will be necessary to rotate the shaft to view the joint through 360 degrees.
Even if the joint appears to be sound, mark the flanges, undo the flange bolts and tie the shaft up on one side. Position a DTI (clock gauge) on the axle with the contact ball on the face of the AXLE drive shaft flange. Rotate the axle so that you obtain at least two full rotations of the flange and check the DTI reading to establish the flange face is within 0.002 inch maximum run out. With care it is possible to clamp a pointer to an axle stand to use as a gauge if a DTI is not available, but the gauge is a better option.

If the runout checks out (doubtful) ensure the male lip on the drive shaft has not been distorted and will fit cleanly and perfectly into the matching recess in the axle flange.
Very likely you will find the axle flange is distorted. The reason is that the flange has been removed at some time to replace the felt seal, by an “operator” directly using a three leg puller. Having rebuilt some 70 to 100 of these S2/S3 differentials I cannot remember many flanges that were not distorted and all were re-machined as a matter of course.

The flanges need removing with a block puller that is a puller that has a 360 degree contact face with the flange and is bolted to the flange. If you find it necessary to machine the flange make sure the female inset on the flange face is machined out to a depth of 0.100 inch to accept the mating drive shaft flange.

It is difficult to sense noise issues remotely but I hope you may get some clues from the above.

(Message approved by david_gore)
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David Balfour
Prolific User
Username: sidchrome

Post Number: 149
Registered: 2-2009
Posted on Tuesday, 05 March, 2019 - 09:14:   Edit PostDelete PostView Post/Check IP

Hi Norman, thank you again for your sage advice. You are indeed like a walking repository of practical experience of many rolled into one. I will be removing the drive shaft shortly, it would now appear, so I will definitely check the pinion flange runout while the shaft is out, in case it needs to come out also.

At the moment the shudder is so extreme that there is something more serious going on. I'm expecting to find the Detroit coupling with a couple of deep wear marks at the point of normal contact with the balls. If logic serves me correctly, the Detroit (Ball and Trunnion) coupling does not maintain the effective mechanical transfer point at a constant radius from both shaft axes and thus must produce the exact same sinusoidal transfer velocity as does a normal Cardan joint.

In other words the ball and trunnion is not a CV joint. But of course it can also account for necessary changes in shaft length as per a splined slip joint. So in principle, the one ball and trunnion should be able to be replaced with a UJ and a slip joint, and I see on a video of Ronny Shaver discussing this, that it is indeed the case.

https://www.youtube.com/watch?v=1szoyRY4RHY

Obviously the axial deflection is small enough that the velocity oscillations are small enough to be inconsequential. I know from logic that UJ's are best used in pairs providing the gearbox output and differential pinion mating flanges at the extreme ends remain parallel, so that the velocity oscillations produced by the first can be cancelled out by the second if orientated with the yokes aligned on the same shaft.

So in theory to eliminate any oscillation during drive shaft deflection between gearbox and centre bearing a CV would be a better technology, but the offset would be more weight, a shorter life (probably), and likely less strength also. I wonder if a new Detroit coupling with modern lubricants, better sealing clamps on the boot, and perhaps a service schedule might be as good a result as any.
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christopher carnley
Unregistered guest
Posted From: 81.158.14.218
Posted on Tuesday, 05 March, 2019 - 20:32:   Edit PostDelete PostView Post/Check IP

I should have added that the Detroit ball and trunnion joint was chosen because it doesn't introduce a velocity fluctuation into the rear twin Cardan type Hooke joint arrangement. You will notice that the D J to front shaft is necessarily flat.

The ball and trunnion joint as also much stronger than the Hooke type UJ.

(Message approved by david_gore)
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christopher carnley
Unregistered guest
Posted From: 81.158.14.218
Posted on Tuesday, 05 March, 2019 - 19:35:   Edit PostDelete PostView Post/Check IP

Repack the Detroit coupling with grease and see how it goes. R-R had 3 separate schemes before it was rendered "satisfactory".

P&A Wood do a version where a modern Rzeppa C.V joint is used in place.

(Message approved by david_gore)
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David Balfour
Prolific User
Username: sidchrome

Post Number: 150
Registered: 2-2009
Posted on Wednesday, 06 March, 2019 - 09:34:   Edit PostDelete PostView Post/Check IP

Hi Chris, Thanks for the recommendation.
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David Balfour
Prolific User
Username: sidchrome

Post Number: 151
Registered: 2-2009
Posted on Wednesday, 06 March, 2019 - 16:38:   Edit PostDelete PostView Post/Check IP

In principle Chris, the P&A Wood CV version should be the smoothest of all as it does not produce any oscillation in rotational velocity regardless of axial deflection through the joint, whereas a ball and trunnion behaves just like a conventional cardan joint in that regards, being two right angle intersecting pivots. Of course the ball and trunnion also has the advantage of being able to accomodate slip, all in the one relatively strong yet compact unit. Chrysler used almost identical types on their drivelines, and the solution now is a UJ + slip joint, typically when they fail.
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Trevor Pickering
Frequent User
Username: commander1

Post Number: 97
Registered: 6-2012
Posted on Wednesday, 06 March, 2019 - 21:51:   Edit PostDelete PostView Post/Check IP

I have recently replaced my Detroit with a UJ and slip joint shaft and am very happy with the result.
No more vibration
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Christopher Carnley
Unregistered guest
Posted From: 5.80.21.124
Posted on Wednesday, 06 March, 2019 - 19:15:   Edit PostDelete PostView Post/Check IP

When the Bipot joint, later labelled the Detroit coupling was devised way back in the steam car days it was to accommodate the plunging effect of solid axles, later in the de Dion cars, and the Citroen Traction Avant.
I have never seen much if any plunging wear in the Rolls-Royce version, as this is taken up by the rear sliding joint.
There is no definite answer to what was in the mind of the designers but I suspect that the Experimental Department remembered the rapid wear in the front Cardan joint of the Derby Bentleys, by needle rollers just rocking back and forth and not rotating due to the flatness.
As followers of fashion, they did adopt the absurd, antiquated Chrysler Floating Power, EPW where the rocking of the engine takes up vibration.

(Message approved by david_gore)

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