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73-87 Chevy _ GMC Trucks => Interior & Equipment => Topic started by: Dirka on October 30, 2014, 06:46:32 pm

Title: Speedometer not working
Post by: Dirka on October 30, 2014, 06:46:32 pm
Hey all! I need help on how to fix my speedometer, it's WAY off showing 20-30mph going 50+
Motor and tranny recently rebuilt
Title: Re: Speedometer not working
Post by: VileZambonie on October 30, 2014, 07:10:40 pm
Sounds like your speedometer is working but is inaccurate. Why don't you tell us about your driveline configuration and what you are working on so we can better help you?

Year, Make, Model, Engine, Trans, Final drive ratio, C or K, 10, 20, 30 etc
Title: Re: Speedometer not working
Post by: BidEquation78 on October 31, 2014, 09:11:08 am
I have the same problem with my 82 C10 (350,th350,regular 85mph speedo). I believe it's due to a worn out speedo gear in the transmission but it could be just worn out internals in the cluster.
Title: Re: Speedometer not working
Post by: 78BIG-TEN on October 31, 2014, 10:47:04 am
My 78 was reading way off,took to shop that calibrates them.At 60 it read 75,so he calibrated to 60 =60,dropped down to 30 and it read 5.Had to re-magnetize and calibrate ,now 30 is30 and 60 is 60
Title: Re: Speedometer not working
Post by: Dirka on October 31, 2014, 04:51:51 pm
It's a 77 chevy K10, 400 and TH350 (automatic) drive ratio i'm unsure of.  I did the, jack rear end up, mark drivetrain, mark wheel, and two full drivetrain rotations was just past one full wheel rotation.