Bristol 400 rear axle gears
 

The rear axle started wining badly. I took the main case out (not a lot of fun! ) and the problem is in the pinion bearings. They are different than what my parts book shows ( tapered versus plain) and in-fact several changes seem to have been made including an oil seal?? This changes the distance within the nose case.
Anybody done this repair?
Thanks,
Dorien Berteletti
In Canada

Bristol 400 rear axle gears
 

Dorien as it happens mine is noisy (they all seem to be) and I'm
sending it to Norman Geeson who you can read about on
www.kda132.com For many years he's specialised in overhauling and
raising the ratios of Post War Rolls-Royce and Bentley rear axles
and he does them for all the top specialists.
He's already done a 403 for someone in the club who'd twice had his
overhauled by axle or Bristol specialists and they'd done so much
damage he had to buy another Crown Wheel and Pinion. Norman did it
properly and it was quiet too.

Norman will have taper rollers ground to fit, he has the special tools
necessary to build the thing and he will spin mine up on the gear
cutter's test rig to find the the quietest setting.

Obviously your being in Canada makes it impractical to have Norman do
it, but once he's done mine, which is possible the same as yours with
the screw in pinion bearing housing, he'll have the bits you need and
be able to talk you through it.

I hope to have it out before Christmas but am currently fitting a
rebuilt Close Ratio Gearbox and MGB Clutch, so would like to see what
it's like before I dismantle it again.

I plan to tour France in it next year (we've five places left if
anyone would like to join us - please email me for details) and would
to reduce the noise as much as possible and be sure that it doesn't
brake down.

Ashley

Bristol 400 rear axle gears
 

Dorien,
By your description it sounds like you could have a 401 -404 type diff
fitted .
Is the pinion held in a separate housing that bolts onto the main
casting that supports the crown wheel carrier. The mesh of the CW & Pinion
is by shims between these housings.

Also check that the crown wheel carrier is not broken where the side
bearings are located.
Regards
Geoff

Bristol 400 rear axle gears
 

Thanks Ashley,
My axle had been quiet and very nice for some years. Then last month all of
a sudden lots of noise as I drove down our driveway. In looking it over more
carefully, there is not much wrong with the pinion bearings.
It seems that the pinion is not being held in place properly and moves.
In looking over your PDF files, the picture on page 26 appears very much
like mine, BUT I have only ONE distance washer were there are 2 shown.
The description on dissassembly talkes about split rings and other locking
devices that do not show up in the picture on page 26.
I have manuals and parts books of my own and they show regular straight
bearings. So I will make up some distance washers and I should be in
business. Will need a new oil seal and may make my own gaskets.
We were in the south of France in October on a brief visit from Italy, were
we regularly tour on our motorcycles. I look forwards to your news from
Norman Geeson.
Cheers
Dorien

Bristol 400 rear axle gears
 

Geoff,
I downloaded info from Ashley's site that I think you helped him with. This
shows the unit I have, and not the one my manual shows.
Correct and so now I see that I may have a later 401 diff. After standing
on my head and cursing 12 times, figured out that the problem is that I have
ONLY one distance washer. Hence no proper bearing adjustment. How this unit
ran quietly for all these years is a mystery.
I will make up new distance washers and then set my lash accordingly.
By the way it would be hard to adjust with shims as it took quite a lot of
tapping and pulling to get the housing off the case .
I have 6" of snow in the driveway so no Bristoling for a while!
Cheers
Dorien

Bristol 400 rear axle gears
 

About the crown wheel carrier. The trunnions where the carrier is supported
by the side bearings are very thin. I became aware of two Arnolts that had
failures there, one of which I had sold. I took a look at the differential in my
last remaining car and found that it had failed as well. The load was being
supported at that point by the half shaft. In the other two cases the gears
were scrambled so I caught mine just in time. So we had new ones made to a design
which is much stronger. This was done by picking bearings that had larger
bores. The machinist that made them made extras and the last time I spoke with
him (2 years ago) he still had some on his shelf. I don't know the situation
now, but if anyone is interested, I can contact him. I can, at least, provide
photos and bearing specs.
Bill Watkins

Bristol 400 rear axle gears
 

Dorien,
(from memory only) , the two tapered bearings on the 401/404 type pinion
are preloaded with a long spacer tube and selective thick ground shims .
This does not adjust the mesh of the pinion with the crown wheel . The mesh
is adjusted by removing or adding thin brass shims between the two castings
as described in a previous email . I've had very little experience setting
the mesh of CW&P but a good starting point is by retaining the original
brass shims that you have.
It would be worthwhile having the CW&P lapped by a diff specialist before
reassembly as Ashley suggested.
Good Luck
Geoff

PS If you find the CW&P is badly worn or damaged there is a company in
Victoria, Australia that has made a small batch of Bristol CW&P's before .
I could make enquiries to get a batch of say 5 - 10 sets made if any one
else is interested.

Bristol 400 rear axle gears
 

> Bill,

I would be very interested in the diff modifications.

Peter McGough> > > > > >

Bristol 400 rear axle gears
 

Geoff,
Thanks.......yes you are correct. In essence there are 2 adjustments. One,
for the bearings using the distance washers that come in different
thicknesses, and the second with the brass shims between the cases. If
either or both are off, then this will affect the CW mesh/lash.
When dismantling it took me some 10 minutes of careful tapping to split the
case and not damage the brass shims. That is what I meant when I said this
is a hard adjustment to make. Hopefully the original shims will do the
trick.
This rear axle seems to have suffered at the hands of some strange people.
Apart from the distance washer already discussed, the main carrier to the
axle itself had 1/2 the studs stripped or broken. I realized this as I was
unbolting it. I will have to drill and tap new threads.
The CW/P are actually in amazingly in good shape.
Thanks
Dorien>

Bristol 400 rear axle gears
 

Peter:
I tried to send a picture of the replacement crown wheel carrier and bearings
but it's in the wrong format for this site. If you (or anybody) will send me
a note to wmw79@aol.com, I will try to send you the picture directly. I called
Wayne Mitchell. He has 2 or 3 units on his shelf.
He can be reached at: wtmitchell@att.net**** He has a website:
www.dogrings.com** (He makes parts for Hewland gearboxes)
Bill Watkins

Bristol 400 rear axle gears
 

Thanks Bill,
Certainly pictures would be good to have. Perhaps you know the Arnolt that
Bill Mac Farling owns, that he converted with a Chev 289.
He changed the rear axle, (Mercury Monarch) to handle the
horsepower.
Cheers
Dorien Berteletti

Bristol 400 rear axle gears
 

Dorien:
The pictures have been sent. I don't know Bill MacFarling but I have seen 3
or 4 Arnolts that were converted to Chevrolet. I almost did it myself after I
cracked a crankshaft, but I came to my senses and bought a new crank. The
suitability of the rear axle was one of the issues. The other was the class (with
Can-Am cars & such) that I would have to run with at the Monterey Historics. It
was only possible to qualify for entry because of some publicity that Wacky
had imported a couple of cars without engines with the intent of installing
Chevys. I asked Michael Arnolt about this and he said that his father had never
followed through on that.
Bill

Diff photos from Bill Watkins
 

The photos from Bill are attached to this post.

Tip: When uploading photos to this site, please ensure you upload individual photo files with an image file extension. The site will only accept .gif, .jpe, .jpeg, .jpg, .png - max image size 1024 x 1024 pixels and max file size 300kb. .pdf is also accepted up to 400kb

Bristol 400 rear axle gears
 

I have previously written about the rear axle on the Bristol, but will
repeat some of what I have said.
First, all the gears for most of the 2 litre cars were made by ENV Gears of
NW London, these were precision ground gears of a very high standard. However,
ENV went out of business (not certain of the date but think it would be in
the later 50's). Bristol had to then resource, and went to Salisbury for the
rear axles which were not manufactured by the same methods and therefore not
as accurate. The result of this was that Bristol experienced noisy axles, so
much so that they had to take action, so appointed Percy Kemish their racing
engine man to sort out the problem. He told me that it took a while but found
that the problem was a quality one and was cured by better finish in
manufacturing, and a more selective fit. (not easy to get right)

Now the workshop manual gives full instructions on setting up the crown
wheel and pinion, and as they have been run together for some time now should not
cause a problem. One point to note is that the ratio is stamped on the
components, and would be most likely a 3.9 or a 4.22 on the overdrive cars.
However some cars which were used for sporting activities had the later ones fitted.

If some of our members do not have a copy of the workshop manual and intend
to work on the cars, they will save themselves a lot of bother by having the
facts to hand.

My regards,
Bellerophon

Bristol 400 rear axle gears
 

My gears are infact stamped ENV 10 x 39. The Pinion and Crown also have the
numbers 2130 handwritten with an indelible marker.
The only damage to the sytem is some slight nicks to the bolt heads securing
the Crown. This would have happened as the pinion slid back as there was no
spacer to hold the bearing/companion flange. The faces are in great shape.
Considering I have toured England, Scotland, Wales, France and a good part
of Eastern Canada, with my 400, I conclude that I am very lucky the pinion
staid in place. It decided to move whilst in the safety of my driveway as I
was leaving for a club event in New England.
Given that you have experience on the subject, there are a couple of points
that you might help me with.

I would be curious to see a picture of the CW bearing caps and their fixed
counterparts. On mine, the castings do not match so as to make a perfect
piece. Infact there is a ledge or notch were the two halves meet. Seems as
if the bearing caps were from a different carrier / casting. Can it be
partly 400 and partly 401? I have sent pictures to the webmaster to
illustrate the point.

Some of the studs that hold the carrier in the rear axle have been crudely
welded on the inside of the case. This caused me much grief as when undoing
the nuts the stud started turning. They could not act as bolts and back
out, because of the welding. Round and around we went.
I had to carefully cut them off with a high speed grinder and now will retap
and repair WITHOUT welding.
Bodges on my car, or has this been seen before?

Regards

Dorien

Bristol 400 rear axle gears
 

Dorien, I am sorry to read that some butcher has managed to get his hands on
your backaxle, but after 60 years with the car passing through several hands
it is sod's law that one could be a butcher.

However, when the axle was new the bearing caps matched perfectly and the
studs were not welded into position, so if you are able to fix this, it would be
good.

Now, do you have a copy of the workshop manual? if not I urge you to obtain
one from the club as the back axle is fully covered (exploded photos also)
with all the information you require. As for the missing spacer in the pinion
drive, you will see that the only major modification was to the pinion, whereby
it went from a screwed assembly to a shimmed one, hence this may have thrown
the butcher.

I am certain that with the right information you will return the car to its
former glory.
My regards,
Bellerophon

Bristol 400 rear axle gears
 

Don't forget that a full workshop manual can be downloaded from the
technical pages of www.jel450.com courtesy of Geofff Dowdle and his
chums in Oz.

Ash

Bristol 400 rear axle gears
 

Yes, already done some days ago. It was those pictures that clued me in.
Thanks
Dorien

Bristol 400 rear axle gears
 

Thanks .....as I suspected. Yes I have my 400 manual and parts book, as
well as having downloaded the 401 manual from Ashley.
Part of my initial confusion was that it looked different from the blowup /
parts of the 400.
Whilst surprises like these are annoyng, the upside is greater
familiarization with the car and "meeting" helpfull and knowleadgeable
people.
Thanks again.

Dorien

Other Bill Watkins parts tips
 

Hi all -

Bill sent me to the right place exactly 4 years ago, when I needed a
new crankshaft. I got the last one "off the shelf" from Henry Velasco at:

Velasco's Billet Crankshafts
12422 Benedict Ave.
Downey, CA 90242
310 - 862 - 3110
Fax 310 - 803 - 1221

Here's a photo before I packed and sent it by air mail to New Zealand:

http://www.frazernash-usa.com/images/crank121404b.jpg

Still ticking!

Bob

Rear axles 400 series
 

Dorien

Ashley James has suggested that I look at this axle thread and make any suggestions that I think may help. Firstly you must understand that I do not necessarily recognise the Bristol Cars by model name or relate car model to axle type, but perhaps you will bear with me on those points. My comments relate to the axle types that were fitted across this car range in general and I hope they might be helpful, and who knows, perhaps illuminating.

Of general interest. When I can get hold of Ashley’s axle, which is the screwed pinion type with that horrible so called ‘semi-thrust’ bearing, it is intended to try to adapt it to taper bearings. They are much more suitable for this particular axle pinion thrust application. The only reason these ‘semi-thrust’ bearing were used is that Timken Taper bearing manufacturing was then in the USA and the British bull dog neither had the Dollars, nor the interest to buy abroad. ENV were in good company even R-R suffered from that muddled thinking and used semi-thrust bearings.

From what I can gather from this web thread, as the facts are in short supply, you have an axle that has tapered pinion bearings and has a crown wheel retained by castellated nuts and bolts. That I believe would mean that the pinion bearings are one off 32307 at 35mm x 80 mm and one off 32206 at 30mm x 62 mm. For the record this axle can be converted to the heavier pinion with the Imperial taper bearings and a Crown wheel that is retained by setscrews, although the manuals tell you it cannot be done. As I have done this conversion and taken photographs, it will eventually be listed on Ashley’s Web site once I have had chance to look over his axle and complete the write up.

The main bearing carrier caps on the differential housing will almost for sure have a ledge as you have shown in your images, and the reason is obviously not understood. I could show you other images of ENV axles, or Salisbury for that matter that clearly show these bearing cap steps. Although the finished housing is line bored with the caps in place and from that point onwards the assembly is kept, sold and fitted as a matched unit, the component parts may be made at different factories. It is the line boring that matters not the external cap fitting, even the materials between the housing and caps can be different. The caps on these axles look as though Leys of Derby may have produced them, and they would only have been rough fettled on their outer edges.

You appear to have had trouble extracting the pinion housing. Ideally it helps to attach a slide hammer to the flange in order that the extraction is square. In any case heat MUST be applied to the differential housing to expand it before attempting to extract the pinion housing. The axle design means that this housing must be tight. As this heating need to be done quickly, because the materials are identical, it is best to use two gas fired blow lamps (If you only have one borrow another from a friend!). Wear leather gardening gloves (Hot housing) and use a copper / hide mallet, whola, it will extract like lightening. Use the same method for refitting the housing. Heat up just enough so it is uncomfortable to touch with bare hands.

There is a general misunderstanding amongst car enthusiasts (and often bearing agents) that the measurements of bearings with the same numbers never alter. On Rolls Royce post war Timken taper pinion bearings for instance; each bearing design has varied in depth by some 0.012 inches over 50 years. This means that a straight bearing change will not only alter the pinion bearing pre-load but also alters the pinion penetration MD position, with two bearings up to 0.024inch. Using the same shims or spacers after a bearing change should be done with caution, and only after the measurements have been checked. Of course utilising the old spacers / shims as a starting point is acceptable, I am not saying the ENV bearings sizing has altered, but I bet they have since the axle was made.

Still on the bearing subject, you will notice these axles have both Imperial and Metric bearings, once again it is not generally known but Imperials are usually made to Positive tolerances and Metric to Negative tolerances. Now you know why that typical Metric 40 mm bearing rarely measures 40 mm! and it can matter if you are swapping over bearings.

I cannot see how your axle can possibly have been in operation for long with the potential pinion bearing end float that you indicate. Are you sure that the small inter bearing spacer did not stick to the outer bearing only to be dropped on the floor later? The bearing forces are quite massive and the end loads are high, which is why axles become noisy as soon as the bearings wear. Failing that I would have thought something had broken, maybe a flange that retains an outer bearing track. Something is strangely amiss.

You will be aware that axles are notorious for being noisy and it is not always obvious to the car enthusiast that the crown wheel and pinion are worn. Often neither gear face will be galled and they will appear polished. What will not be obvious is that they have been running out of line for some time and worn accordingly, this wear will only be apparent to an experienced eye. This axle design is spiral bevel, with the emphasis on “spiral” as the helix angle is very large. These particular axles are nearly as difficult as a hypoid to set up, and the helix angle is as steep as some hypoid pinions. As a general rule the steeper the helix, the more accurate you need to be and the more likely it is to make some noise if you are out with the settings.

You mention making up some spacer washers for the bearings, but I am afraid that if the CW & P are good at the moment, they will have a doubtful life afterwards. Due to wear on the bearings and possibly the gear set it is unlikely that you are going to position the bearings or pre-load them so that they are in the same MD position. In addition you are probably thinking of attempting multiple extractions of the front bearing housing to reshim in order to achieve the backlash…WRONG. This is like adjusting the handbrake cable on a car in order to adjust the rear brakes.

Once the bearing preload has been set, using the lowest poundage tolerance listed in the instance of the ENV axles, then the pinion must be assembled in the correct MD position - 0.001 to 0.0015 inch.

The ONLY objective in setting a CW & P is to have it assembled in the axle in the position in which it was both designed and ACTUALLY CUT. In essence it means that it is necessary to either calculate the pinion manufacturing distance (MD) or better still have the drawings on hand so that the distance can be read off. If anyone has detailed drawings of the Crown Wheel and pinions, I could advise you on how to achieve that setting. This distance needs to be accurate to within 0.001 inch at worst and preferably less than 0.0005 inch and it can be replicated using measuring methods.

This MD measurement sets the only position for the axle pinion and it copies the manufacturing position and sets the pinion an exact distance from the Crown wheel centre. Following this the main bearing carrier adjusters are set to move the crown wheel sideways in or out of mesh to achieve the correct backlash. If you have read the workshop manual you will have read about the dogs dinner method of setting the pinion and crown wheel with marking blue. A method used by those that do not thoroughly understand rear axle gear sets. The average out of position for a pinion set using this method is 0.015 inch, unless a really experienced axle person has done it. Remember no one has tried to build rear axles on a production line using marker blue, they use measurements and rarely get them wrong.

One other small point that has already been mentioned in respect of the axle centre unit. The main bearing carrier trunnions can break across behind the bearing abutment and in my experience this is nearly always caused by one of two faults. The first is a lack of a sufficient radius on the carrier or bearing inner track or more likely the failure of a rear wheel bearing. On no account whatsoever rebuild a rear axle without renewing both rear wheel bearings!!

I trust the points may be helpful, or my mentor, Mr James will be telephoning me bright and early tomorrow morning!


Regards

Norman Geeson
Peterborough
England

Rear axles 400 series
 

Norman,
Thank you for taking the time to write such a detailed and clear explanation
and yes.... certainly illuminating.
I appreciate that with regards to the main bearing caps it is the line
boring that counts. However on other cars that I have worked on, including
Alfa and Hudson, the housing and caps were a very close fit comparable to a
connecting rod. Hence my surprise at the ledge.

You are of course correct on the pinion housing and I did use some heat as
well as gentle tapping to work, but a slide hammer is a good idea. I tend to
use mine for axle shafts and forgot about it on this job. This is what
prompted me to say, that playng around with fitting and removing shims was
going to be a long job. Further on this.......
To reassemble it, I was set to use our kitchen oven and the freezer. My wife
returned in time to discourage me....something about the oily smell
lingering on and doing something to the Christams turkey!
So I improvised, and being in Canada, I set the Pinion housing out on a tray
in the snow and -10c. The main housing was placed in front of a roaring
fire and an hour later the parts slid in very nicely.
Yes you are correct on bearing numbers altering over the years. Glad you
mentioned it, as some people don't beleive this can happen. Found it out
the hard way years ago.

I am also perplexed at how this axle worked for so long. To recap: Worked
fine for some 5 years + whatever miles the previous owner put on. He died
before I could met him and althoughI have an extensive file on the car, the
rear axle is not mentioned. In October it started whining badly at the rear
as I drove down the driveway one day. It had been fine the day
before.Basically this happened suddenly not gradually.
I backed it in to the garage, jacked it up on all 4 wheels on special
stands and had my wife "drive " the car while I listened. I then got under
( engine off and gearbox in neutral) and found I could move the output shaft
at the pinion considerably. I suspected a broken bearing. I left it and
returned to it several weeks later and dismantled the unit.
The nut with it's locking tab securing the companion flange to the pinion
was still in place, but the flange could be pushed in and out enough that
the pinion touched the Crown nuts and this caused and or contributed to the
noise. When I dismantled the unit, it did not match what I expected to see
from my manual. Then via this site I was told I probably had a 401 shimmed
adjustment unit. I pulled a picture off of Ashley's site ( courtesy Geoff)
and also went through some of my own files. So now I could see what I had
and what I did not have. I was missing the spacer washer that sits between
the companion flange and the taper bearing. Without it you can't preload the
bearing very well. I made one up as per the thickness quoted in the manual.
I can see now that I have more threads showing from the pinion than I had
before dismantling it. In other words the pinion has now been drawn up
properly on/against the bearings. I must assume that the bearings were
never loaded properly.

I agree that it is strange it worked well for so long but I don't have any
other explanation. There were no broken pieces or bits falling out. The oil
seal and companion flange would keep any loose pieces inside.

No I was not planning multiple extractions to set backlash as this will not
set backlash. I mentioned extractions as given that this unit is called a
"shimmed adjustment type" some poor sod must have spent time heating and
cooling to get the unit opened and closed and different shimms tried. As
mentioned above.

I agree with the MD measurement but not having the actual specs, I used a
dial indicator for a initial backlash, and then mounted a pulley to the
companion flange and belt drive to a variable speed electric motor. I
lubricate the unit and run it up and listen for axle whine and adjust
accordingly.
Probably not the most scientific but it has served me well on other axles
and I preferr it ot the "marking blue". If you should try this, make sure
you are wearing a bow tie and not a regular tie!

And yes the wheel bearings will be renewed.
Thanks again for the invaluable help and confirmation on some strange
thoughts on bearings. And anybody else who can come up with a "why" the
pinion floated.......please let's hear from you.

Regards

Dorien Berteletti
Toronto
CANADA

Rear Axles 400 Series
 

DORIEN

I am hoping that along with this post you will be able to see the steps that are present adjacent to the ENV axle main caps. I just hope the attachment works.

It does not surprise me that you found the axles fully fettled on the Alfa etc, but the ENV was an industrial type unit offered out to specialist car builders, or as an option for their normal fitting. The need to keep costs at a minimum meant that fully finishing a unit that could not be seen would be out of the question.

Regards

Norman

Rear Axles 400 Series
 

Norman,
Thanks for the links. Yes,.... they clearly show the steps we talked about.
I had posted pictures of mine a week or so ago, and some of us thought that
the steps were due to mismatched castings and although bored/machined to
size, nevertheless a bit of a bodge. You have helped us to better understand
the way ENV produced their units.
Thanks again
Dorien