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09-29-2010, 10:33 PM
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#1 |
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Registered User
Join Date: May 2009
Location: Wisconsin
Posts: 27
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Speedometer Off
Ok, so I just got the 52' back on the road after putting it back together the past couple years..... one slight problem.
My speedometer is off about 10mph at 55mph. It's a new speedometer out of the box from Dolphin Gauges. Its a mechanical gauge, that just hooked up to my 350 turbo with the speedometer cable. I didn't notice any adjustments on the back of the gauge when I had installed it last summer. Before I run it over to the local speedometer shop, is there anything I could be missing to try first? Thought I would add a photo of the almost completed truck..... 
Last edited by bmnk; 09-29-2010 at 10:34 PM. |
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09-29-2010, 10:42 PM
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#2 |
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Registered User
Join Date: Jul 2010
Location: Elk River, MN
Posts: 614
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Re: Speedometer Off
I'd guess it is the spedo gear in the trans
here is a calculator http://www.tciauto.com/Products/Tech...eedo_gears.asp
__________________
55 2nd series Chevy Pickup 2019 Chevy Equinox(Daily driver) 2011 Chevy Malibu (Wife's car) MSRA Member I went to a bookstore and asked the saleswoman, "Where's the self-help section?" She said if she told me, it would defeat the purpose. -George Carlin |
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09-29-2010, 11:53 PM
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#3 |
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Registered User
Join Date: Sep 2010
Location: Plano, TX
Posts: 319
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Re: Speedometer Off
Need to add a tooth or drop a tooth on the speedo drive gear in the trans depending on if its 10MPH up or down. should get you in the 2-4 legal MPH range deviation.
Last edited by Wheelie; 09-29-2010 at 11:53 PM. Reason: Jim beat me to it! but mies easier :) |
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09-30-2010, 03:49 AM
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#4 |
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Registered User
Join Date: Mar 2003
Location: San Francisco, CA USA
Posts: 2,454
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Re: Speedometer Off
You will need to replace one or both of the speedo drive gears in the transmission. In order to get the correct gears, you will need to know your tire diameter and rear axle ratio.
Ray |
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09-30-2010, 08:40 AM
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#5 |
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Yellow truck club
Join Date: Apr 2006
Location: Barrie Ontario
Posts: 2,080
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Re: Speedometer Off
change your rear tire size .....
__________________
................................................................ Brian ......  My hub garage address http://www.hubgarage.com/mygarage/59apache I gue$$ everything has it'$ price ALL GONE NOW   59 Chev Apache PRAISE THE LOWERED 350 700r lokar shifter power MII front end, shockwaves tilt, 4 wheel discs 4-link and bags 10 bolt limited |
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10-01-2010, 06:40 PM
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#6 |
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Registered User
Join Date: Oct 2005
Location: Overland Park, Ks.
Posts: 5,229
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Re: Speedometer Off
Most 350's use the large speedo gear. Pull it out of the trans. & the number of teeth will be on it or count them. If the speedo is too fast put in a gear with about 2 teeth more. If it is slow put one in about 2 teeth less. They are available from a parts store in the Motor Mite line. You can compare the odometer with the mile markers on the freeway. As you pass one note the 10'ths reading. Go to about 2 more markers & note it again. If you have gained tenth's it is too fast & vice versa. You can juggle gears till you get it real close.
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10-01-2010, 10:31 PM
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#7 |
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Registered User
 
Join Date: Jul 2007
Location: Toppenish, WA
Posts: 15,711
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Re: Speedometer Off
If you have access to a handheld gps take the truck out and figure out exactly how far it is off. probably at 60 mph on the speedo. Then figure out what percentage you are off and after counting the teeth on the driven gear and matching the color of the drive gear you can figure out what gear set will give you the right speed. You can get them at a local transmission shop, your GM parts counter or online. This outfit has a lot of good info on their website. It will pretty well walk you through without any real guesswork http://www.transmissioncenter.net/sp...FQEziQod3SGNeQ
You have to scroll down not quite half way down the page for turbo 350 info and pieces. Last edited by mr48chev; 10-01-2010 at 10:34 PM. |
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