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04-20-2010, 09:51 AM
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#1 |
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Registered User
Join Date: Nov 2008
Location: Crosby, Texas
Posts: 377
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Speedo off 20 mph
I changed the dash in my 72 Burb and the speedo is 20 mph. When I am registering 40mph on my speedo I am actually only going 20mph. Can this be corrected or do i need to switch out the dinstrument panel again? I thought a plastic gear can be changed in the tranny, but I know nothing about that.
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" I never think of the future. It comes soon enough " - Albert Einstein |
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04-20-2010, 09:56 AM
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#2 |
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*************
 
Join Date: Apr 2005
Location: Pensacola, FL
Posts: 17,837
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Re: Speedo off 20 mph
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Rob - https://www.instagram.com/hart_rod_c10 As Iron Sharpens Iron, So One Man Sharpens Another. Proverbs 27:17 FOR SALE: DBW pedal bracket - http://67-72chevytrucks.com/vboard/s...d.php?t=651123 FOR SALE: Hood Brackets http://67-72chevytrucks.com/vboard/s...d.php?t=679945 1987 Silverado SWB - 34.5K original miles http://67-72chevytrucks.com/vboard/s...d.php?t=801834 1969 SuperBurb - http://67-72chevytrucks.com/vboard/s...d.php?t=200387 1968 Farm truck - http://67-72chevytrucks.com/vboard/s...d.php?t=358692 1968 SWB - http://67-72chevytrucks.com/vboard/s...d.php?t=551258 1948 Chevy - http://67-72chevytrucks.com/vboard/s...=122164&page=3 Last edited by Hart_Rod; 04-20-2010 at 09:56 AM. |
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04-20-2010, 01:08 PM
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#3 |
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Spanked once
Join Date: Oct 2006
Location: Intheshop, Indiana
Posts: 969
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Re: Speedo off 20 mph
That is weird..what was the change in the dash? I'm not aware of differences in the gauge ratio unless the old or the new has some sort of corrector on it. Be a different story if you did a change with the trans.
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The ole 350 budget build. |
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04-20-2010, 04:39 PM
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#4 |
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Parts and more parts
Join Date: Nov 2003
Location: Lebo, Kansas (middle of nowhere
Posts: 6,821
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Re: Speedo off 20 mph
I agree on that the instrument panel change should not have made a difference, UNLESS the speedo is FUBAR. I would try to calculate if the difference is the same at all speeds or if it gets worse or better as the speed is changed on the road. That should tell you is the speedo is not working right, vice the gear ratios. However the gear change is not hard if you go to your tranny shop or the NET and do a little "Driven" and "Drive" gear research. There are different teeth numbers and the colors of the gears usually denote the number of teeth.
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Frank |
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04-20-2010, 08:35 PM
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#5 |
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Registered User
Join Date: Mar 2008
Location: summerville, sc
Posts: 93
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Re: Speedo off 20 mph
I think I have the same problem. I seems to be off the same amount. I think mine is because I changed from a 3 speed manual to a TH350. Not sure.
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04-20-2010, 08:53 PM
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#6 |
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Registered User
Join Date: Feb 2007
Location: Cali Central Coast
Posts: 5,191
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Re: Speedo off 20 mph
There is a little calibrater you can put on at the tranny - check at your speedo shop,
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'67 SWB Fleetside ZZ4/350/Tremec 5-speed/4link/Scott's IFS - and fun as heck! SOLD  Click here to support the board Philippians 4: 6-7 |
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04-21-2010, 08:09 AM
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#7 |
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Registered User
Join Date: Jun 2002
Location: central pa
Posts: 1,525
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Re: Speedo off 20 mph
Check and make sure your speedo cable is fully inserted in the speedo meter and tighten down. I have seen loose cable cause a similar problem.
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72 longhorn c30 502BB/th400/fact air/4.11rear/ custom camper 72 bug(the better half's) under reconstruction 2009 HHR aqua blue 71 GMC k20 350/sm465 2009 Chevy hd3500 6.6 Victory Red crew cab dually Dave & Jeanne |
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04-21-2010, 08:54 AM
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#8 |
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Registered User
Join Date: Nov 2008
Location: Crosby, Texas
Posts: 377
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Re: Speedo off 20 mph
Thanks for the suggestions. When I bought the Burb the speedo did not work at all. I had a couple of spare instrument panels laying around so I picked one and installed it. Me thinking that all panels were equal, I didn't label them as I removed them. The burb is a half ton and has a 402 big block with the TH400 Tranny which I haven't changed. Still not clear if the Instrument panels have different ratios for different applications. However I did change the tire size but not the rim size.
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