Bristol 400 rear axle gears

[Hydroglen]

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

[Ashley James]

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

[Geoff Dowdle]

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

[Hydroglen]

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

[Hydroglen]

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

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

[Geoff Dowdle]

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.

[412usa]

> Bill,

I would be very interested in the diff modifications.

Peter McGough> > > > > >