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Odometer reading ok. Speedometer is not.

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Old Aug 19, 2012 | 03:12 PM
  #1  
kissedin's Avatar
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Car: Trans Am
Engine: 305
Transmission: TH350
Odometer reading ok. Speedometer is not.

Hi.

I Have a 82' firebird trans am with 305 engine (carbs) and TH350 transmission.

My speedometer is giving me a reading that is around 27 - 30 % too fast.

I've looked in to changing gears but then I discovered that my odometer is correct.

1. Can i fix this issue with changing speedometer gears?
2. If my speedometer is broken, is there a way to repair/recalibrate it?

Any help greatly appreciated / Björn
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Old Aug 20, 2012 | 12:29 AM
  #2  
Marine_Marauder's Avatar
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Joined: May 2012
Posts: 167
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From: Santa Clara, CA
Car: Black 1991 Z28
Engine: 5.7 TPI
Transmission: Automatic
Axle/Gears: I have no Idea
Re: Odometer reading ok. Speedometer is not.

Originally Posted by kissedin
Hi.

I Have a 82' firebird trans am with 305 engine (carbs) and TH350 transmission.

My speedometer is giving me a reading that is around 27 - 30 % too fast.

I've looked in to changing gears but then I discovered that my odometer is correct.

1. Can i fix this issue with changing speedometer gears?
2. If my speedometer is broken, is there a way to repair/recalibrate it?

Any help greatly appreciated / Björn
First things first,

Are you reading the MPH or the KM?





J/K
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Old Aug 20, 2012 | 07:58 AM
  #3  
kissedin's Avatar
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Car: Trans Am
Engine: 305
Transmission: TH350
Re: Odometer reading ok. Speedometer is not.

I'm reading the KM/h. When i'm traveling in 50 km/h the meter shows 65. When i go in 80 the meter shows around 110.

My odometer is calibrated for km/h and seems to be accurate.
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Old Aug 24, 2012 | 11:09 AM
  #4  
kissedin's Avatar
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Car: Trans Am
Engine: 305
Transmission: TH350
Re: Odometer reading ok. Speedometer is not.

Trying to bump this thread. Since I have a carburated engine (LG4) there is no VSS to take into consideration. It seems my only option is to replace the speedometer.

Or does anyone know a way to repair it? (I've checked my shopmanual but all it's saying about my problem is that the speedometer needs to be reparied. duh)

Any help greatly appreciated / Björn
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Old Aug 24, 2012 | 11:16 AM
  #5  
Apeiron's Avatar
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From: Mercedes Norte, Heredia, Costa Rica
Car: 1984 Z28 Hardtop
Engine: 383 Carb
Transmission: 4L60
Axle/Gears: 3.54 Dana 44
Re: Odometer reading ok. Speedometer is not.

Wouldn't matter if there was a VSS, if the odometer right then the problem is still in the speedo head mechanism.

No user-serviceable parts inside a speedometer. Pretty much has to go to a shop for remagnetization and recalibation.
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Old Aug 24, 2012 | 12:51 PM
  #6  
kissedin's Avatar
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Car: Trans Am
Engine: 305
Transmission: TH350
Re: Odometer reading ok. Speedometer is not.

It wasn't the answear I was hoping for. But it is an answear. Thank you.
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Old Aug 29, 2012 | 03:54 PM
  #7  
kissedin's Avatar
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Joined: Jun 2012
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Car: Trans Am
Engine: 305
Transmission: TH350
Re: Odometer reading ok. Speedometer is not.

For the record: According to the papers from "transportstyrelsen" a govt. authority in sweden my odometer should read kmh. But it does not. Before ordering a new speedo a checked with a GPS more thoroughly than I did before. My odo reads miles. And it reads around 23% too much. Next step is to find the right gears or simpy order an ratio adapter. Have posted this in the trans. part of this wonderful forum.
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Old Aug 30, 2012 | 11:31 AM
  #8  
Marine_Marauder's Avatar
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Joined: May 2012
Posts: 167
Likes: 1
From: Santa Clara, CA
Car: Black 1991 Z28
Engine: 5.7 TPI
Transmission: Automatic
Axle/Gears: I have no Idea
Re: Odometer reading ok. Speedometer is not.

I would try swapping out the instrument cluster. They're on Ebay all the time.
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