This may be news to everyone here, but the speedo problems May have a real
simple fix. The 4 wheel drive industry has a large variety of screw on gear
reducers/multipliers for truck that add begger tires, i.e. Lift kits.
these are small little devices. You remove the speedo cable from the
tranny, screw on the multiplier in its place, and the connect the speedo cable
to the multiplier. The ratios within the little gear boxes are selectable.
This is far better than changing the driven gear in the tranny. Leave it stock,
so the gear mesh / wear ratio is the same, and do all of the changing
externally in the little multiplier. They're pretty cheap too.
Rich
-----Original Message-----
From: Steve Laifman <Laifman@Flash.Net>
To: James Barrett <jamesbrt@mindspring.com>; Tiger's Den <tigers@autox.team.net>
Date: Wednesday, June 03, 1998 8:33 AM
Subject: Re: Speedometer Cable Questions
>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. >
>
>
>_/_/_/_/_/_/_/
> _/ _/_/_/ _/_/_/ _/
> _/ _/ _/ _/ _/ _/ _/_/_/_/
> _/ _/ _/ _/ _/ _/ _/
> _/_/_/_/_/__/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/
> _/
> _/_/_/
>
|