Tony, my original posting was worded using my best guesswork figures since
I don't have a car on which to actually make tests and report exact
numbers. I believe most experienced engineer would accept my remarks as
being pretty accurate enough for the purpose intended.
I may be mis-reading your last comment in which you seem to state that you
"toured with the 3.89 gears and have added a OD unit to THOSE gears??? "
This would raise the mph/rpm data to where 1000 rpm would make about 24mph.
Carrying this data out to your "cruise speeds of 3000-3500 rpm, this means
you cruise I-5 at 72-84 mph .
You also mention that the car has nice low rpm response in OD !
I too would like OD for highway touring use, but would want the proper gear
ratio that OD works best at. I simply have a hard time seeing how a stock
engine could have nice low rpm response when pulling 3.11:1 drive ratio you
seem to now have.
We all know the word "lugging" which means asking the engine to produce the
power needed for a certain mph, at too low an rpm. Lugging is very harsh
on bearings, rings, pistons and anything else which feels the power
produced at too low a rpm. Oil pressure is not up to full psi and water
circulation may also be below optimum for safe sustained running.
In Colo. we have long mt. passes where a car may be on an upgrade for 45
minutes or more. In such sustained strain, you would want to shift out of
OD to let the engine "breath" and reduce bearing stress etc. etc.
High revs DO NOT harm a normal engine, particularly small size import
engines which can easily spin a 4000-4500 (and higher) all day long without
any abnormal wear. These same small engines get wrecked or at least have
early overhauls is they are continually made to work hard at lower rpm.
I trust you will consider all this and perhaps avoid OD on hills at least.
Jarrid has posted some additional remarks which I also endorse as being
correct and appropriate to your situation.
Dick T.
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