speedometer question - Hot Rod Forum : Hotrodders Bulletin Board
Hotrodders.com -- Hot Rod Forum



Register FAQ Search Today's Posts Unanswered Posts Auto Escrow Insurance Auto Loans
Hot Rod Forum : Hotrodders Bulletin Board > Tech Help> Electrical
User Name
Password
lost password?   |   register now

Reply
 
LinkBack Thread Tools
  #1 (permalink)  
Old 09-09-2010, 06:19 PM
Registered User
 
Join Date: Mar 2009
Location: greeneville, tn
Posts: 94
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
speedometer question

i know it's not electrical, but this is the closest place that it fits.

my wife's 1985 ss monte carlo's speedometer is screwed dead up. it reads 5-10 mph slow while it's below 35-40 mph, but after that it starts bouncing around. i pulled the cable out of the speedometer housing & it looked good, so i'm thinking it's the speedometer or the speedometer gear in the transmission (2004R overdrive.) what would you think?

    Advertisement
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2 (permalink)  
Old 09-09-2010, 08:22 PM
cobalt327's Avatar
WFO
 
Last wiki edit: Intake manifold
Last journal entry: 1980 Malibu Wagon
Last photo:
Join Date: Mar 2009
Location: Atlanta
Age: 60
Posts: 5,036
Wiki Edits: 1616

Thanks: 128
Thanked 598 Times in 547 Posts
Quote:
Originally Posted by the nitro man
i know it's not electrical, but this is the closest place that it fits.

my wife's 1985 ss monte carlo's speedometer is screwed dead up. it reads 5-10 mph slow while it's below 35-40 mph, but after that it starts bouncing around. i pulled the cable out of the speedometer housing & it looked good, so i'm thinking it's the speedometer or the speedometer gear in the transmission (2004R overdrive.) what would you think?
It could be the cable rotating at an erratic speed from rust, damage, wear, frayed cable wires, bent/kinked cable or cable sheath, damaged or worn speedo gears/gear housing at the trans.

This can cause the speedo needle to jump, but wouldn't necessarily cause the speedo to read slower than it should. For that to happen because of the cable, it would need to turn slower- which it cannot do w/o almost immediate failure.

If you don't find anything wrong w/the cable, gears, etc., what can also be causing your problem is the speedo head itself. It works by a flying magnet driven by the cable, spinning inside a steel hub that has a needle attached to it.

The hub is pulled along by the rotating magnet; it tries to "catch up" to the magnet, and this is what causes the needle to indicate your speed. If there's any unneeded drag on the hub- caused by dirty or tight bearings, or a build up of dust and dirt inside the mechanism- this can cause a lower than expected reading and an erratic needle.

A thorough cleaning w/a soft brush and a can of compressed air will often be enough to put the speedo back into service. This will require that the dash be partly disassembled to get to the speedo head. Once it's out and you're able to clearly see it, you'll likely see the problem.
Reply With Quote Quick reply to this message
  #3 (permalink)  
Old 09-09-2010, 08:36 PM
Registered User
 
Join Date: Mar 2009
Location: greeneville, tn
Posts: 94
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
i took the gauge cluster out of the dash, that's how i got the cable out of the liner. the cable lloked good. the speedo looked good & didn't feel tight or anything. i guess i'll pull the speedo gear from the transmission & look at it.
Reply With Quote Quick reply to this message
  #4 (permalink)  
Old 09-09-2010, 08:53 PM
cobalt327's Avatar
WFO
 
Last wiki edit: Intake manifold
Last journal entry: 1980 Malibu Wagon
Last photo:
Join Date: Mar 2009
Location: Atlanta
Age: 60
Posts: 5,036
Wiki Edits: 1616

Thanks: 128
Thanked 598 Times in 547 Posts
FWIW, most inner cables can be removed from the outer cover from the trans end OR the speedo head end- whichever's more convenient. In your case, you needed to look at both ends anyway, so it's all good.

You will need to check the cable inch by inch- looking (and feeling- just don't stab your finger or hand w/a piece of broken wire ) for any frayed wires or a shiny and/or worn area that would indicate the inner cable has been binding at that point.

The speedo cable runs right beneath the back side of the inner fender cover (probably made of plastic) and a flat tire that sheds its tread can slam into the fender cover and the speedo cable w/quite a bit of force.

This same area is prone to having road salt, water, dirt, etc. constantly thrown onto the cable cover- especially if the inner fender cover's damaged already.
Reply With Quote Quick reply to this message
  #5 (permalink)  
Old 09-10-2010, 03:28 PM
Registered User
 
Join Date: Mar 2009
Location: greeneville, tn
Posts: 94
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
the g body cars cable has to come out from top. they have a crimped on block that won't let them pull from the bottom. i put a new cable in it today & it fixed it. i looked at the cable again & it was perfect. it must have been in the housing, but there wasn't any marks or even scratches on it. it's fixed thats all i care about. 10 bucks wasn't to bad on the wallet neither.
Reply With Quote Quick reply to this message

Recent Electrical posts with photos

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Hot Rod Forum : Hotrodders Bulletin Board forums, you must first register.
Please enter your desired user name (usually not your first and last name), your email address and other required details in the form below.
User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.




Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

Posting Rules
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
383 stroker 73monte Engine 11 05-07-2014 09:08 AM
supercharger.... 73monte Engine 16 07-24-2010 11:27 AM
2004 Silverado electric speedometer Deuce General Rodding Tech 8 10-28-2008 08:04 AM
Ignotion Set-ups Native Gearhead Engine 8 11-29-2003 02:20 PM
nitrous 69BiRd Engine 2 11-28-2003 11:33 PM


All times are GMT -6. The time now is 05:49 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
Copyright Hotrodders.com 1999 - 2012. All Rights Reserved.