Seven Differential Bearings
'The Austin Seven
Manual' by Doug Woodrow includes a story of the
special pair of special 'narrow outer ring' Angular
Contact front crankshaft ball bearings initially
fitted to the 1934-39 crankcase and the problems
which can be caused when using standard bearings
with the two different housing depths (page A2-45).
The same 'narrow outer ring'
bearing problem also applies to the Angular Contact
differential pinion thrust bearings introduced at
the same time. There is no reference to this in
either Woodrow or The Austin Seven Companion, so
let us investigate.
When a pair of
angular contact bearings were introduced to the
torque tube to take pinion thrust in 1931 these
also had the 'narrow outer ring' design- as were
the two crown wheel side AC bearings 1929/39 and
the 1929/30 pinion front (flange) end bearing.
The Austin Motor Company, used the narrow special bearings
which they called Double Purpose Bearings.
The June 1931
Austin 7 Parts List 670F lists the special narrow
outer ring bearings, but the March 1935 list 1218A
only lists standard bearings, which could indicate
that later differentials were equipped with the
design of angular contact bearings allows for a
pair to be mounted back to back or face to face but
these Austin specials with the 'reduced' outer ring
width must always be mounted back to back.
A prewar SKF
Austin Seven bearing application listing shows
these Differential Bearings as W number specials
and a discussion with an SKF bearing history
specialist gave the following information-
Pinion Front (Flange) end - W 6535 (can be
replaced by RHP MJT 7/8, SKF AMS 7 - Spares Number 0391 )
Differential Side - W 6356 (later I-132509)
(can be replaced by RHP LJT 1 1/4, SKF ALS 10 - Spares
Pinion thrust - 2 x W 6898 (can be replaced by
2 x RHP LJT 1, SKF ALS 8 but see below*)
(Also refer -
Hoffman N 1917, R&M 3-LJT 1, FBC LBS10AC )
All of these W
number special bearings had a 1/32" reduced width
outer ring on the non thrust side.
In the 1929/30
differential the pinion front bearing RHP MJT 7/8, SKF AMS 7
will correctly replace W 6535 with no change
In the 1929-37
differential the side bearing RHP LJT 1 1/4, SKF ALS 10 will
correctly replace W 6356 with no change
*In the 1931/32
differential, fitting a pair of standard full width
angular contact pinion bearings RHP LJT 1, SKF ALS 8 in place
of W 6898 will displace the pinion toward the crown
wheel by 1/32" and cause the housing C nut to sit
1/16" out. To correct this, the torque tube bearing
seating must be machined 1/32" deeper and 1/32"
taken off the C nut face to fit the wider outer
rings- but see below-
*In the 1932-38
differential, with the pinion thrust bearings
mounting in a separate housing, fitting a pair of
standard full width angular contact pinion bearings
RHP LJT 1, SKF ALS 8 in place of W 6898 will place the pinion
away from the crown wheel by 1/32". To correct
this, the bearing housing must be machined 1/32"
deeper and the torque tube clamping face reduced by
1/32" to fit the wider outer rings- but see below-
*To avoid machining the housings when fitting new bearings
Spares have had pairs of bearings re-machined to the early outer ring width,
narrower than the inner ring.
Austin 7 Club
Spares listings for these new special Angular Contact Bearings-
Pinion thrust bearing - RHP LJT 1 special, SKF ALS 8
special, Club Spares Number 0394a