[Healeys] Dave Dougan's overdrive part 2

[Bob Spidell]

Uh oh ... here comes another 'oils' thread ;)

re: "... non detergent formulation. This formulation allows contaminants 
to settle out and not be continually re-circulated, thus hastening 
damage..."

Though I defer to Dave's knowledge and experience, this 'theory' never 
made sense to me, mostly because a properly cleaned and assembled 
gearbox and O/D should not have any contaminants.  They are pretty much 
sealed and won't suffer any combustion byproducts or other 
contamination.  When I've changed my gearbox and O/D oil, there was 
always a minuscule amount of brass 'shake' suspended in the oil which 
sparkled prettily in the sunlight.  I guessed this was an amount of 
brass about the size of a B-B that had been ground into infinitesimally 
small particles.  When rubbing the 'shakey' oil between my fingers I 
could feel absolutely no grit whatsoever--it felt just like virgin oil.  
There was usually a very small amount of ferrous metal on the magnets in 
the O/D strainer, even with ashless dispersant-- aka 'detergent' oil, so 
the heavier stuff was settling out anyway.

Given that brass is a relatively soft metal, and most high-quality 
greases are oil thickened with finely-ground metals--molybdenum, 
lithium, etc.--I believe the finely ground brass causes no harm at all 
and may, conceivably, be a lubricant and/or protectant in its own 
right.  I feel the only reason to even change the oil is because the oil 
molecules will be sheared over time and may lose some viscosity; though 
the fact that modern differentials call for never even changing the oil 
may belie that belief.

I have over 165K miles on my gearbox and O/D with one rebuild on the 
gearbox only and they both operate quite well.


bs

*******************************************************************
Bob Spidell           San Jose, CA            bspidell at comcast.net

*******************************************************************