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73-87 Chevy _ GMC Trucks => Interior & Equipment => Instrumentation => Topic started by: Rustbucket86 on July 22, 2015, 11:16:11 am

Title: Speedometer question.
Post by: Rustbucket86 on July 22, 2015, 11:16:11 am
My 86 c10 is reading 75 at 60mph. It has stock tire size. The previous owner said it started when he took the dash apart to change out the high beam indicator light in order to pass inspection. Should I just get a new cable, a new speedometer, or find a shop to recalibrate the old speedometer?
And if I need a new speedometer cable, can anyone confirm if an 1986 long wheel base Silverado 305 2wd 4 speed needs the 80" or 61" cable? Thanks in advanced.


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Title: Re: Speedometer question.
Post by: zieg85 on July 22, 2015, 11:23:43 am
Verify the speedometer is off and the odometer is correct.  If you travel a mile and that is what the odometer shows then the speedometer needs attention.  If you are not a purist on the mileage than get a used one.  You can get a whole cluster from a pick and pull for $35 or so. 
Title: Re: Speedometer question.
Post by: Rustbucket86 on July 22, 2015, 12:52:31 pm
Odometer moves too fast as well.


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Title: Re: Speedometer question.
Post by: zieg85 on July 22, 2015, 12:55:47 pm
That indicates a wrong speedometer gear in the transmission not a faulty speedometer.
Title: Re: Speedometer question.
Post by: Rustbucket86 on July 22, 2015, 01:36:01 pm
But it worked fine until the speedometer gage was removed once to replace the high beam indicator light. No transmission work was done at that time.


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Title: Re: Speedometer question.
Post by: Rustbucket86 on July 22, 2015, 01:39:33 pm
The previous owner had to change the bulb in order for the truck to pass inspection, and was moving hastily and got frustrated because he didn't know how to unclip the gauge from the cable and did some tugging on it initially.


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Title: Re: Speedometer question.
Post by: enaberif on July 22, 2015, 03:07:38 pm
Put some dry graphite into the end on the speedometer side and then disconnect both ends and spray cable cleaner through it.
Title: Re: Speedometer question.
Post by: zieg85 on July 22, 2015, 03:35:13 pm
Usually even hastily removing it by pulling on the cable that clip holds it and shouldn't mess with it any.  If it is original trans, original rear end and original tire height then it should all work fine.  Purchase a used one and throw it in, if it fixes it great but I have not heard one act like you are describing all of a sudden...
Title: Re: Speedometer question.
Post by: bd on July 22, 2015, 04:29:23 pm
Quote from: Rustbucket86 on July 22, 2015, 01:36:01 pm
But it worked fine until the speedometer gage was removed once to replace the high beam indicator light. No transmission work was done at that time.

If the PO removed the speedometer head from the cluster, he may have accidentally damaged the movement or nudged the needle on its shaft knocking it out of calibration.  Take the vehicle to a speedometer shop and have it checked.
Title: Re: Speedometer question.
Post by: Stewart G Griffin on August 02, 2015, 06:17:04 pm
What size tires originally came with the truck?
Title: Re: Speedometer question.
Post by: Brocksdad1 on August 30, 2015, 08:17:12 pm
Take out your speedo. Clean it well and use the grafite  or thin oil on its workings. Make sure the tabs on the bell aren't touching the bell. If all is original speedo will be correct. I had to take my pointer and spin it back while looking at the spring to in a sense retention it.

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