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Jumping Speedo Needle

To: "The List" <tigers@autox.team.net>
Subject: Jumping Speedo Needle
From: "Mike Sutter" <mjsutter@cts.com>
Date: Fri, 2 Mar 2001 19:27:34 -0800
Mark F. wrote the following:

"Listers:
    I have a question I was hoping I could get some help with. My
speedometer needle jumps as I drive down the road."


Mark,

I had the same problem with my speedo. It turned out my speedo cable was
fine.

The problem was that the two small nylon, or similar material, odometer
drive gears inside the speedometer were cracked radially from the axle hole
out to the teeth. These cracks caused a pitch change between two of the
teeth on each gear. When the crack in the gear rotated around to the spot
where they meshed with the other gears, the pitch mismatch caused  the
mechanism to bind up momentarily then release. This constant repetitive
binding caused the needle to bounce every time those small gears did 1
revolution.

Maybe a rebuild is in order. Plenty of guys have had their speedos rebuilt
and I'll let them speak for themselves.

I am replacing the gears in mine.

Your problem with putting the drive cable back in the sheath may be caused
by an extreme bend in the sheath at some point along its route to the
trans. Trace the routing from the back of the speedo to the trans and look
for a tight radius bend. If you find one, try to work some slack to that
area and increase the bend radius there. Then try and re-insert the drive
cable while gently spinning it with your fingers. As a last resort, pull
the sheath out of the car and straighten it out on the shop floor and
..... you get the picture.

Mike Sutter
'66 Tiger

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