[Healeys] BN1 Gearbox Leaks

[Rich C]

Hello all,

Over the years we've all seen the early 3 speed BN1 gearbox and how much they
seem to leak oil. They seem to leak out of every possible joint, flange,
gasket, plug, seal, and so on. The average BN1 will leave not just a drip from
one spot, but usually from 3 or 4 places.

Recently I worked with a local but really excellent machine shop to develop a
nitrile quad ring seal that is inserted into a machined groove in the front
cover scroll surface area. This was developed very carefully to give adequate
engineering tolerance so the seal would not chafe, but seal effectively to the
smooth first motion shaft area.

All the other possible leak prone areas were dismantled, cleaned thoroughly
and new gaskets and seals were installed wherever required. The gaskets were
"painted" with Permatex 300, as were any bolts that thread into oil areas(side
cover, front cover, etc. I figured with all this attention to the problem we
should get a pretty leak proof gearbox.

Just to make sure of things, the breather on the overdrive unit was checked
that it was clear to do it's job.

The results?

No leaks when topped up and sitting motionless.

Drove the car about 5 miles, and the drips were worse than ever!

Theory: These gearboxes cannot breathe adequately. The only breather for the
whole assembly is not in the gearbox portion, but way at the back in the
overdrive. The only opening to this breather is through the gearbox rear
bearing spinning with a film of oil. hardly an adequate breathing system.
How did they breathe when new? Perhaps enough atmospheric pressure release was
allowed through the original reverse scroll design on the first motion shaft
and cover?

Do I now need to drill, tap and install a breather on top of the gearbox
casing?

Thoughts? Norman Nock, are you reading this?

Rich Chrysler