Speedometer reading high??
Thread Starter
Drifting
Joined: May 2001
Posts: 1,651
Likes: 13
From: Holly MI
Speedometer reading high??
My buddy replaced the speedometer cable in his 69, and now the speedo is reading too high. I can't figure out how the speedo would do this. We are thinking maybe it was reading low with the old cable, so the previous owner put the wrong gear in. Now, with the new cable, it's reading high. What do you think? I searched, and found threads for bouncing/jerky speedo's, but nothing for reading too high.
Thanks for the help.
Ken
Thanks for the help.
Ken
Burning Brakes
Joined: May 2004
Posts: 1,201
Likes: 2
From: Frederick Md
Originally Posted by bb69
My buddy replaced the speedometer cable in his 69, and now the speedo is reading too high. I can't figure out how the speedo would do this. We are thinking maybe it was reading low with the old cable, so the previous owner put the wrong gear in. Now, with the new cable, it's reading high. What do you think? I searched, and found threads for bouncing/jerky speedo's, but nothing for reading too high.
Thanks for the help.
Ken
Thanks for the help.
Ken
The plastic gears that slip into the tranny case determnine what speed the Speedo reads...and they are COLOR CODED...
RED BLUE TAN GREEN etc...each specific to the number of teeth on the gear..
Dr Rebuid sells them cheap BUT more important, they list the number of teeth and the color codes... pull the gear you have now and count the
number of teeth ..then pick up the phone and order a gear that will read
lower.. (I never remember if more teeth read lower or higher..but the catalog tells you... Removing the gear is a 2 minute job !
Bob G.
64 72 76 79 & 98 Vettes
Racer
Joined: Mar 2005
Posts: 487
Likes: 0
From: Jacksonville FL
all he replaced was the cable? that should have had no effect on your speedo reading at all.
as stated above, you need to change your speedo driven gear. if it is reading too high, you need a gear with more teeth. if it is reading too low, you need a gear with less teeth.
on a manual trans, each tooth will make about a 3.3 MPH change in your reading.
what transmission do you have?
i know a web site that can help you figure out which gear you need, but that link is on my computer at home. i will try to remember to post it for you when i get home.
hope this helps,
Mike.
as stated above, you need to change your speedo driven gear. if it is reading too high, you need a gear with more teeth. if it is reading too low, you need a gear with less teeth.
on a manual trans, each tooth will make about a 3.3 MPH change in your reading.
what transmission do you have?
i know a web site that can help you figure out which gear you need, but that link is on my computer at home. i will try to remember to post it for you when i get home.
hope this helps,
Mike.
Burning Brakes
Joined: Jun 2005
Posts: 764
Likes: 2
From: THE OLDER I GET THE BETTER I WAS! NORTHERN ONTARIO
Maybe the old cable was binding so then someone changed the gear to try & match the speed...then the cable let go...you may have the wrong gear now that the speedo cable works properly, that could explain why you have a higher speedo reading...just a guess
Racer
Joined: Mar 2005
Posts: 487
Likes: 0
From: Jacksonville FL
Originally Posted by G dad
Maybe the old cable was binding so then someone changed the gear to try & match the speed...then the cable let go...you may have the wrong gear now that the speedo cable works properly, that could explain why you have a higher speedo reading...just a guess
i think it's more likely that he removed an adapter in the process of changing the cable. some of these adapters are 1:1, but most of them are either reducing or increasing adapters.
Burning Brakes
Joined: Jul 2004
Posts: 1,235
Likes: 0
From: Sick of these TOOLS & AZZHATS in DC
yeah....damn....this is like "Twilight Zone" stuff here because MY speedo is reading too high now too!!
WTF??? I just swapped out my stock TH350 with a Hughes TH350 and I used the SAME driven gear (removed from my old trans) and the SAME cable and now I'm reading 20+ MPH over!!!(it's the first time I've actually seen my needle go past 140mph
) I asked my wife if she saw any black helicopters hovering over the house or gremlins lurking in the garage
but she said no...something very very strange is goin' on here....
WTF??? I just swapped out my stock TH350 with a Hughes TH350 and I used the SAME driven gear (removed from my old trans) and the SAME cable and now I'm reading 20+ MPH over!!!(it's the first time I've actually seen my needle go past 140mph ) I asked my wife if she saw any black helicopters hovering over the house or gremlins lurking in the garage but she said no...something very very strange is goin' on here....
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Racer
Joined: Mar 2005
Posts: 487
Likes: 0
From: Jacksonville FL
bb69, try this link to figure out what speedo driven gear you need:
http://www.tciauto.com/tech_info/speedo_gears.htm
http://www.tciauto.com/tech_info/speedo_gears.htm
