Jim,
As usual, your information is accurate. I don't know about the MkII speedo, but
it's simple to check. Just look at the speedo face, and the number is printed
at the bottom. I'd like to know, based upon my closing sentence. British
practice has always been to customize the speedo, vs. US practice of 1000 rpm =
60 mph and make the gearing cause that to be true. They may have changed, but
that would be a change. If you have a MkII, look at the face and see if it
say's 980 or 1000. I've seen very high numbers when Alpine added an overdrive.
Need on of these for my son's OD Alpine.
Since the stock tire is no longer available (or wanted), everybody is running
something that invalidates the calibration (which includes rolling tire
radius). As usual, they tend (as I did) to pick larger diameters. This causes
the speedo to read lower than normal, as the rpm is the same, but the distance
traveled is greater. To correct this with a cable gear requires a reductio in
the tooth count. Since the Tiger already has next to the lowest available, you
get 1 tooth less, if you can find it. Your calculations show that this amounts
to a correction of about 3%, or 1.8 mph at 60. I don't think that will help
much. The other sizes go the wrong way. Changes in "higher" rear end ratios,
of course, go the other way.
Changing the transmission shaft helical gear is a valid approach, if available
in the count you want. This, of course, requires a tear-down of your removed
tranny. Lot's of time and bucks. You want to be especially careful about both
grears as Ford made them pitch in different angles, depending upon design. Got
to match up pitches. Left twist vs. right twist.
I don't know about the MkII, but the MkI had 15 toothed cable gears. I think
14 is the smallest number Ford makes (if they still make it).
Steve.
Did get a MAJOR speedo adjust, however, when I installed a MkII tranny in a
MkI. Calibration was made on the speedo,. with the MkI box, requiring 1080
revs/mile vs 980 stock. (2.88 rear end, 180x13 R on 4.5 rims). With the change
to the MkII the calibration was way off again. A check on the free Auto Club
dyno proved I really wasn't doing 80 on the freeway. The change, based upon the
cable-turns method, came out with a 1280 revs/mile requirement!!!!. Now I can't
seem to go as fast as I used too, without passing a lot of cars. {8->
Steve
Steve Laifman < One first kiss, >
B9472289 < one first love, and >
< one first win, is all >
< you get in this life. >
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