[Healeys] Overdrive status

[BJ8Healeys]

Hello, Healeyphiles -

 

A couple months ago, I posted a message about slipping of my overdrive,
which I thought was probably caused by worn sliding clutch linings.   Since
I last rebuilt the O/D in 1993 (81,300 miles ago), it has always worked
perfectly until recently and the slipping seemed to occur suddenly.  When
the slipping occurred, there was also a "whizzing" sound from the O/D.  List
wisdom said it was low oil pressure.  I thought y'all might be interested in
the results.

 

I bought a pressure gauge and a road test confirmed that the oil pressure
was low, at 365 psi rather than the 450 psi required.  Disassembly of the
O/D revealed one of the piston rings for the accumulator lying intact in the
bottom of the accumulator bore, along with the multiple-piece remains of
another ring.  Amazingly, the bore of the accumulator was undamaged - except
for a small burr on the extreme edge of the bore which I could probably have
polished out, but chose to replace the accumulator housing along with the
piston and rings.  I also replaced the O-rings on the operating pistons.

 

The bronze thrust washer for the unidirectional clutch was found broken into
multiple pieces.  The spring in the clutch was there, but not engaged.
There was a crack through the complete thickness of the clutch roller race.
One of the rollers had an area of spalling on one end of the surface, with
other rollers having smaller surface defects.   Mostly because of the crack
in the race, I decided to replace the aft section of the O/D with a spare
BJ7 unit.  I replaced all of the (3) thrust washers and shimmed the sun
wheel to the end float spec of the manual.  Thanks to lister George Haywood
for designing and building a neat test rig so we could spin up the gearbox
and overdrive before reinstalling in the car and for traveling the 70-mile
roundtrip to my house on several days to assist.  The test showed 450 psig.
Now that it's all back in the car, the O/D kicks in RIGHT NOW when the dash
switch is turned on.  We just returned from a 600-mile "test run" and the
O/D worked flawlessly.

Thanks also to Magnus Karlsson for his patience in answering my many
questions during the process and to Dave Porter for helpful hints.   In
1993, there was no convenient resource to rely on except the shop manual and
I had forgotten a lot of the things I learned before (or thought I did..).


 

Happy Healeying!

Steve Byers

HBJ8L/36666

BJ8 Registry

AHCA Delegate at Large

Havelock, NC