[ROVERNET - UK] Diff ratio check
agale at iinet.net.au
Fri Nov 25 01:30:39 GMT 2005
Well that's what it is **supposed** to be, but then my engine is
supposed to be a rover 10 - but in the rebuilding we found it had been
bored out to a 12 at some stage (prompting some gasket exchanging).
So I am not taking anything for granted! The gearbox has 10hp stamped
on it, so that seems original.
However in the meantime i have worked out that it is a 4.88-1 diff - one
wheel in the air turns twice for just under five turns of the prop
shaft, which according to "how stuff works" and a couple of restoration
and idiots' guides is the best way to check.
Reckon the best thing is to run the car as it is for a few months after
assembly, let the engine run in and then consider options depending on
how she performs. Unrestored she was surprisingly eager (much more
lively than the Cyclops); so expect her to be a very strong car. She is
very lightweight (very easy to push around in the garage, unlike the
Options therefore include:
1) a longer crown wheel and pinion (say 4.0 - 1) - will take some expert
advice on this
2) an overdrive unit
3) no change at all. (Why try to make it something she is not?)
According to my maths, the engine will be revving at 3750 rpm at 60 mph
(the book says I get 16mph/1,000 revs) which is a bit much for direct
poured big ends and I am more interested in having a comfortable highway
touring speed (ideally able to cruise at 60-65) than have a fast takeoff
at the lights (which will never be an option without remaking the gear
clusters to produce a special close ratio box. A little overdrive unit
is appealing, but screams of modernity.
I think if anything needs doing, I will go for a crown and pinion
makeover (a lot more cosmetically appealing and a 1930s possible
I am told that if it is the original rover 10 diff, there is not another
one that can be used as a swap because of splinal conflicts. I have a
spare diff and spare gearbox to experiment with, so there is plenty of
time to muck about without taking the car off the road.
Thanks for the input and advice, as ever.
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