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Speedometer problem????

A

Anonymous

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Took my 69 to a cruise in last night about 45 miles from home. Was cruising about 70 MPH. Then all the sudden the speedometer started to drop. RPM stayed the same but speedometer kept falling fianlly down to about 45 MPH. I stopped in a small town to wait for a buddy to show up. Took off again and speedometer seemed fine again. About 5 miles up the road it starts to act up again. Then about half way home it was acting up and them all the sudden jump up to normal and was fine the rest of the way home. What does this sound like to you? Speedometer was not bouncing just reading slow.
 
Could be twisting in half internally in the cable housing or the gear on the end of the cable in the transmission could be stripping.
 
Two things. Plastic gear on speedo to trans is wearing out [most likely] or rounding out cable at dash on one end or the other. Has any work been done in that area lately and how long has it been working?
 
Not to hijack, but the timing is perfect... I noticed mine bounced quite a bit last night while I was driving around. I know the repop is quite a bit longer than the stock piece, should I check for binds?
 
Odd that is just dropped down like that. Have you pulled the speedometer cable from both the trans and instrument cluster to inspect the ends?

Do you have the standard non-tach speedometer or do you have the one with the tripmeter? If it comes down to being a bad speedometer I may have one you can have for the cost of shipping. I believe there is a way to lubricate the internals of the speedometer with something like what they use to lubricate clock internals.
 
The slowly dropping is very common with a gear starting to wear out. The hotter the gear gets, the less grip the worn teeth have and things tend to slip. I have had that happen on two older vehicles. Check the gear. While there, turn the cable by hand and see how well it turns.
 
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