Ben writes:
>I have a late 1200 Herald Saloon with a 1500 Dolomite engine.
>As the gearbox (as far as I'm aware) is the original 1200 one, would the
use of an overdrive conversion kit
>increase the car's performance. I know very little about these (I would
even appreciate a quick explanation of how
>they work) but it seams that the poor gearbox is having to cope with more
power than it was designed for.
>Yours, becoming less ignorant each digest
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Ben,
The overdrive will allow more relaxed cruising by lowering the rpm at
freeway speeds. It will not give you any performance gains, but will
probably improve your mileage on the freeway - and will NOT improve the
reliability or power handling of your transmission as you use your existing
tranny and simply bolt an overdrive on to the end where the tailshaft was.
Actually it's not all that 'simple' as the main shaft, rear mounting,
driveshaft, and wiring/relays/switches all have to be added/changed. It's
actually easier to just swap an overdrive adapted transmission with your
current one, but you will still need to do all of the above except change
the mainshaft. It's still quite a bit of work. The easiest way to determine
what type of tranny you have is to first look at the output flange, the one
that bolts to the driveshaft. If it's square as opposed to round than you
have an early no-synchro first (crashbox, Andy M. are you listening?)
transmission. If the flange is round, than look at where the shifter
extension bolts to the top of the case.. If you have a long casting housing
the shifter and shift rail, open at the bottom, attached to the top of the
tranny with 4 nuts, than you have a later 3 rail tranny. If the top of the
transmission has a large flat cover plate with 9 bolts holding it on and a
single shaft going to the shifter extension mounted on the tailshaft, than
you have a later 'single rail' marina type box (the strongest). Of course
it helps to have the tranny cover off :-) Hope that helped somewhat.
Barry Schwartz in San Diego,CA
Bschwartz@encad.com
72-V6 Spitfire (undergoing T5 transplant)
70 GT6+ (daily driver for now)
70 Spitfire (body repair on hold see above)
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