Rover P6B Differential Pinion Extension Housing

Rover P6B Differential Pinion Extension Housing

I have placed this enquiry in the gearbox section because there is no Rear Axle section that I can find.

I have a second hand rear axle pinion housing extension that I am about to overhaul before installing it as a replacement item into my P6B. Then, the unit from my car will become the Rover Car Club of Australia's service exchange unit.

However, I do have some questions:

All literature I have found so far, informs that the harmonic damper must not be disturbed. The question(s) is (are): Is the harmonic damper 'tuned' to a particular rear axle's characteristics? Or, once the factory set the damper in position on the extension housing, could the assembly be swapped from car to car? And, finally, how serious is the situation with an ill-tuned harmonic damper and housing assembly installed in a motor car?

It is understandable that my aim is to be sure that an exchange system can operate reliably.

Thank you,

Mike Allfrey.
 
Hi Mike

I am a little mystified by your approach here. I've never heard of anyoner seperating a diff extension from the diff for whatever reason before. I would expect anyone with a problem to simply replace the bearing and oil seal at the front of the housing in-situ.

But to answer your question - yes I would expect the harmonic damper to be positioned to suit the complete diff and extension pair. I'm not certain what the effect of a mispositioned one is, though. I have heard of people getting driveline vibration at higher speeds, but it is extremely difficult to dissentangle the cause from the combination of tyres, the six UJ's and the harmonic damper.

Rover did appear to go to some trouble in pursuit of this - dampers are not all in the same position - so one could infer from this that Rover thought it was worth the effort!

Chris
 
Dear Chris,

Thank you for your advice. This job is quite involved. The main reason for reconditioning a pinion extension housing assembly is because, when my car is over my pit, the workshop roller doors have to stay open. Leaving the car there while I am chasing a new bearing would certainly break the drought here in Melbourne! Besides, the open doors would let the possums in. I was looking for a quick change over.

Another point, I don't have a bearing specification and so can't find one at a local bearing supplier, where such would be of Chinese manufacture and I am looking for either SKF of Ransome and Marles bearings to replace the one I have. However, I will extract the bearing in the spare housing I have here. Then, when the seal and gasket arrive from JRW I can set to work.

Once the housing is removed from my car, I will compare the harmonic damper positions very carefully. I was hoping to start an exchange housing assembly service for the local Rover Car Club. Certainly, if the harmonic dampers are found to be differently located - well, the scheme will fall in a heap!

Is there a P6B bearing cross-reference list available? One of those would be handy down here.

I was talking to the previous owner of my P6B today, who had done a full body restoration on the car, about the rear wheel hub bearings. He assured me that the bearings had never been touched. So, the complete absence of grease from the one bearing in the LHS hub must constitute some sort of record for a Timken taper roller bearing running without grease. In my car's case, probably 37 years!

Kind regards and keep up the good work,

Mike A.
 
When chasing vibrations on my car I was advised to fit the damper because it never had one
 
Thank you for the comments.

I have dismantled the spare extension housing and was delighted to find that the bearing is a common 6205 ball race. It is, for the record, 25 mm inside diameter, 52 mm outside diameter and is 15 mm wide. It is also stamped with 'England' on the outer race.
Now the task is to find a British made bearing - not an Asian imitation.

I am still interested in the harmonic damper. The extension housing I have dismantled has, four plain washers between the outer arch and the lower bracket that the bolts thread into. At each side, there is a larger OD plain washer beneath the outer arch's slots, which makes good assembly sense. The three round rubbers are located centrally within the similar diameter pads cast into the housing. As far as I can determine, adjustment of the harmonic damper is by the number of plain washers above and below the outer arch piece. Any fore and aft positioning of the assembly could look a bit strange. I assume the proper location of the round rubber blocks would be in the centre of the similar diameter casting pads.

I do not yet know whether the rubber pads are bonded to either the damper components or the extension housing itself.

Having now seen the rear axle input shaft's slimness, I will use the accelerator pedal with a degree of decorum!

With respect to my car, it is very smooth, throughout the rev range in all three speeds of the auto box.

All the best,

Mike A.
 
That input shaft is indeed a knowm failure point, Mile! An upgrade to a better material does the trick, availabe off the shelf from Classeparts. Of more cocern, thpough, are the output stub shafts. Alan hasn't tackled a remanufacture in better material yet as the choice is between a huge billet to start from or a tricky weld between the shaft and flange.

Chris
 
Thank you for that! I will now feather the accelerator pedal with due care. I must say that, I am very surprised at the mention of the differential side (output) shafts shearing, what with all the Land Rover experience.

Chris, the input shaft must be a very good piece of steel. It is probably up there with the Ford Model 'T' half shafts. The late Claude Himms, of the Nailsea Garage, Nailsea near Bristol, when making a new connecting rod for my moped back in 1957, used a piece of Model 'T' half shaft for the task. That connecting rod never broke! Claude also got the balance of the rotating parts correct. That engine ran smoother than previously.

I would venture to think that the output stub shafts were machined from a forging. I don't think they would have been machined from a steel bar, nor would I think they were machined from a cast iron blank. Cast steel, maybe.

Thank you for the information about an upgraded input shaft from Classeparts. I will try and find their Website.

Thank you for all the advice, it is greatly appreciated,

Mike Allfrey. Melbourne.
 
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