[Mgs] Overdrive Numbers

[Paul Hunt]

Back in November 2007 a topic cropped up that appears from time to time, on 
just how many cars were equipped with overdrive for the North American 
market, opinion being that it was quite small.  As well as wondering why 
this should be, I also wondered how it compared to the UK, where I'd have 
said overdrive was more the rule than the exception.  I live quite close to 
BMIHT and enquired about access to the records and they said it would be 
possible, although I didn't really want to have to go through all 
half-million individual build records (although a few sample ones would be 
fun).  It occurred to me that 18V engines had prefixes which indicated 
whether OD was fitted or not - presumably the engine/gearbox assembly was 
ordered and received as a complete unit, so all I really needed was records 
of the purchase orders for these from Abingdon to Engines branch.  I *then* 
realised that the information had been staring me in the face all along, as 
it is included in Clausager in the Engine section.

They make interesting reading.  From November 1973 (when the engine number 
indicated whether OD was fitted or not) to the end of production there were 
48,457 engines fitted to Home and non-North American export cars, of which 
fully 97% had overdrive (they were standard in Home market cars from the 77 
model year onwards).  For North America from August 71 (engines for this 
market were separately prefixed at an earlier date) of 186,542 engines only 
17% had overdrive, which is a huge difference to other markets.  There are 
other interesting differences.  When Canada had its own engines from August 
1975, and California from June 1976, more than 25% had overdrive, while in 
the same period the USA other than California only had 17%, another 
significant difference.  Even odder, when Japan had Californian spec for the 
last few months of production, they were 100% equipped with overdrive.

So why did so few North American cars have overdrive?  And why did Canada 
and California have significantly more than the rest of the USA?

Full figures at http://www.mgb-stuff.org.uk/wn_gearsframe.htm and click on 
'Overdrive - How popular was it?"

PaulH.