My Speedometer reads too fast - 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> Transmission - Rearend
User Name
Password
lost password?   |   register now

Reply
 
LinkBack Thread Tools
  #1 (permalink)  
Old 03-25-2003, 08:55 AM
Member
 
Join Date: Nov 2002
Location: Beverly Hills
Posts: 442
Wiki Edits: 0

Thanks: 1
Thanked 0 Times in 0 Posts
Post My Speedometer reads too fast

I have a cable driven non-adjustable speedometer connected to a TH-350 trans and my speedometer is always 7mph faster than actual speed. I presently have an 18 tooth gear in the trans. Should I go to a 19 tooth or 17 tooth gear to adjust the reading? Someone once told me one tooth adjustment will deliver about a 5 mph correction. Thanks for the Advice!

    Advertisement
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2 (permalink)  
Old 03-25-2003, 09:25 AM
willys36@aol.com's Avatar
Hotrodders.com Moderator
 
Last wiki edit: How to rebuild a Rochester Quadrajet 4MV carbureto...
Last journal entry: How to change auto shift timing on 200R4
Last photo:
Join Date: May 2002
Location: Bakersfield
Posts: 8,384
Wiki Edits: 21

Thanks: 1
Thanked 4 Times in 4 Posts
Post

I fix these problems by going down to my local speedometer shop and having them put in an auxiliary gear box that precisely corrects the difference. Cost is something less than $100 and you end up with a laminated spedometer calibration certificate. The gear box simply screws in between the cable and the tranny using the standard large swivel nuts. Check your phone book. Most medium sized cities have spedo shops. The cheapest alternative is just drive 5mph faster all the time!
Reply With Quote Quick reply to this message
  #3 (permalink)  
Old 03-25-2003, 11:54 AM
Deuce UK's Avatar
New Member
 
Join Date: Dec 2002
Location: Leavenheath, England
Age: 54
Posts: 19
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Post

jpd37, take a look at this site.Speedo Gear Selection

changing the gear is easy....if you dont know that already. that calibration box sounds cool. I dont think we could get them in the UK. Getting the gear for my TH350 was hard enough.
Reply With Quote Quick reply to this message
  #4 (permalink)  
Old 03-25-2003, 03:31 PM
bullheimer's Avatar
NEVER use credit cards!
 

Last journal entry: car with tt2's, (stockers going back on)
Last photo:
Join Date: Jan 2002
Location: North of Seattle
Posts: 2,529
Wiki Edits: 0

Thanks: 0
Thanked 5 Times in 4 Posts
Post

if you got that box hanging off the tranny it's like $29 at GM. speedo shop will tell you what to do. by the way, howz things in BH? i went to BHHS 69-71

[ March 25, 2003: Message edited by: bullheimer ]</p>
Reply With Quote Quick reply to this message
  #5 (permalink)  
Old 03-25-2003, 04:40 PM
airworld2's Avatar
Member
 
Last photo:
Join Date: Mar 2003
Location: houston texas
Posts: 583
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Post

how can you have a non adjustable speed o are you dealing with a chevy 350 trans or buick olds or pont? they make different outside gears for all the above. the rule I've learned 1 tooth on driven gear is about 3 miles an hour. use known car or truck with accurate speedo to check after you replace outside gear they cost about 5-10 bucks from your local gm dealer.add teeth to driven gear(outside gear) to slow down subtract teeth to read faster.

[ March 25, 2003: Message edited by: airworld2 ]</p>
__________________
airworld2
Reply With Quote Quick reply to this message
  #6 (permalink)  
Old 03-25-2003, 04:46 PM
Member
 
Last photo:
Join Date: Sep 2002
Location: USA
Posts: 490
Wiki Edits: 0

Thanks: 0
Thanked 2 Times in 2 Posts
Post

I like this calculator it makes it so much easier.
Reply With Quote Quick reply to this message
  #7 (permalink)  
Old 03-25-2003, 04:57 PM
Jon's Avatar
Jon Jon is offline
Hotrodders.com Administrator
 
Last wiki edit: Removing stuck fasteners Last photo:
Join Date: May 2001
Location: Colorado
Age: 37
Posts: 3,206
Wiki Edits: 7314

Thanks: 0
Thanked 12 Times in 9 Posts
Post

Here is a link to a search for "speedometer calibration" in the Hotrodders Knowledge Base. Hope that helps .
Reply With Quote Quick reply to this message
  #8 (permalink)  
Old 04-02-2003, 09:37 AM
Member
 
Join Date: Nov 2002
Location: Beverly Hills
Posts: 442
Wiki Edits: 0

Thanks: 1
Thanked 0 Times in 0 Posts
Post

Thanks Jon for the tip on the hotrodder's knowledge base. I have not learned how to use this site altogether yet, so the link really helped. I bought a new speedometer driven gear after doing the calculations and the fix is less than 1 mph off. Fantastic! The total cost of the fix was $3.35. Hard to beat and I don't have another gizmo to fail on me. Thanks to all with tips, ideas and advice. This continues to be the best site for information!
Reply With Quote Quick reply to this message

Recent Transmission - Rearend 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:
If you do not want to register, fill this field only and the name will be used as user name for your post.
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



All times are GMT -6. The time now is 03:57 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.