Weird Speedometer question
Thread Starter
Racer
Joined: Mar 2001
Posts: 272
Likes: 3
From: Marion Ia
Weird Speedometer question
My speedometer will read up to about 25 miles an hour and then it will drop to 0. When I slow down it will start bouncing again at about 20 mph. After I drive for a while it will not register at all. I have tried a new cable with no help. I had the tranny out over the winter and it has not acted right since I got the car running again. I have checked and and the speedometer gear is tight on the cable and acording to the AIM all the parts are in and correct. Is this the behavior of a speedometer that is going out and needs to be rebuilt?
Racer
Joined: Dec 2005
Posts: 325
Likes: 0
From: Partlow VA
Easy way to check if the speedometer and cable is good, pull the speedometer cable off the trans and connect a variable speed drill to the end of the cable (I think you need to run the drill in reverse?) Run the drill SLOWLY and see what the speedometer does, if it working the problem lies in either the drive gear or the driven gear. My problem turned out to be someone had the drive gear on the wrong side of the retainer clip on the output shaft. You can check to see if the drive gear is lined up with the driven gear once you pull the driven gear housing. 
Thread Starter
Racer
Joined: Mar 2001
Posts: 272
Likes: 3
From: Marion Ia
Originally Posted by Vettkeeper
Easy way to check if the speedometer and cable is good, pull the speedometer cable off the trans and connect a variable speed drill to the end of the cable (I think you need to run the drill in reverse?) Run the drill SLOWLY and see what the speedometer does, if it working the problem lies in either the drive gear or the driven gear. My problem turned out to be someone had the drive gear on the wrong side of the retainer clip on the output shaft. You can check to see if the drive gear is lined up with the driven gear once you pull the driven gear housing.
thanks for the pointers looks like another fun weekend.
Heel & Toe
Joined: Apr 2004
Posts: 24
Likes: 0
From: Indianapolis IN
Is the speedo cable lubed well?
A jumpy speedometer is sometimes caused by not having the cable lubed well. Sometimes you can disconnect at the transmission, pull the inside out, and grease it and slide it back in and reconnect the cable.
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From: Gladstone MO
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Another possibility is the speedo driven gear ( the cable goes into it) is worn and not getting the cable to turn all the time. Unusual, but I have seen it. Normally the cable is dry, binds up in the housing and then spins the speedo, and repeats.