Parts Catalog Accessories Catalog How To Articles Tech Forums
Call Pelican Parts at 888-280-7799
Shopping Cart Cart | Project List | Order Status | Help



Go Back   PeachParts Mercedes-Benz Forum > Mercedes-Benz Tech Information and Support > Diesel Discussion

Reply
 
LinkBack Thread Tools Display Modes
  #1  
Old 03-11-2021, 09:54 PM
Registered User
 
Join Date: Aug 2019
Location: Ellicott city, MD
Posts: 229
Speedometer registers 5mph fast

Hi,

My 1983 300d has a speedometer that registers 5 mph too fast.
The odometer works perfectly.
The tires are the recommended size for the car.

Any idea what may be causing this. It currently has 83K miles on it and it has always been this way since my ownership of 17K miles.

Thanks.

Reply With Quote
  #2  
Old 03-11-2021, 10:09 PM
Banned
 
Join Date: Nov 2020
Posts: 188
Normal. Mechanical speedometers were never accurate.
Reply With Quote
  #3  
Old 03-12-2021, 02:25 AM
Registered User
 
Join Date: May 2007
Location: Out in the Boonies of Hot, Dry, Dusty, Windy Nevada
Posts: 9,657
Your 83 300D should have the 3:07 Differential.
To check it, look at the Differential from the rear.
lower left corner scrape off the grease/grime and
there is a set of #`s stamped.

The Spedo has a part # also 123 xxx xxx xxx
use to have a list of what #`s went with what Diff.
Some one may have it.
The Diff and Spedo are a set that go together.

Yeah could just be off because of being mechanical.


Charlie
__________________
there were three HP ratings on the OM616...

1) Not much power
2) Even less power
3) Not nearly enough power!! 240D w/auto

Anyone that thinks a 240D is slow drives too fast.

80 240D Naturally Exasperated, 4-Spd 388k DD 150mph spedo 3:58 Diff

We are advised to NOT judge ALL Muslims by the actions of a few lunatics, but we are encouraged to judge ALL gun owners by the actions of a few lunatics. Funny how that works
Reply With Quote
  #4  
Old 03-12-2021, 08:31 AM
Registered User
 
Join Date: Oct 2020
Location: Michigan
Posts: 29
My 83 300SD does the same
Reply With Quote
  #5  
Old 03-12-2021, 09:40 AM
Registered User
 
Join Date: Jan 2006
Location: Tucson, AZ
Posts: 5,358
Search function.

http://www.peachparts.com/shopforum/diesel-discussion/238488-backyard-speedometer-adjustment.html


http://www.peachparts.com/shopforum/diesel-discussion/230116-any-way-calibrate-w123-speedo-2.html
__________________
“Whatever story you're telling, it will be more interesting if, at the end you add, "and then everything burst into flames.”
― Brian P. Cleary, You Oughta Know By Now
Reply With Quote
  #6  
Old 03-13-2021, 02:18 AM
Registered User
 
Join Date: May 2007
Location: Out in the Boonies of Hot, Dry, Dusty, Windy Nevada
Posts: 9,657
That`s a few years back, forgot about adding to these posts.
Haven`t taken a spedo apart in a few years. they are pretty simple.




Charlie
__________________
there were three HP ratings on the OM616...

1) Not much power
2) Even less power
3) Not nearly enough power!! 240D w/auto

Anyone that thinks a 240D is slow drives too fast.

80 240D Naturally Exasperated, 4-Spd 388k DD 150mph spedo 3:58 Diff

We are advised to NOT judge ALL Muslims by the actions of a few lunatics, but we are encouraged to judge ALL gun owners by the actions of a few lunatics. Funny how that works
Reply With Quote
  #7  
Old 03-13-2021, 03:41 AM
Registered User
 
Join Date: Aug 2019
Posts: 949
Quote:
Originally Posted by dsvw View Post
Hi,

My 1983 300d has a speedometer that registers 5 mph too fast.
The odometer works perfectly.
The tires are the recommended size for the car.

Any idea what may be causing this. It currently has 83K miles on it and it has always been this way since my ownership of 17K miles.

Thanks.
If you have a 1985 speedometer in a 1983 car then it will show 5mph faster at around 70MPH.

1985 cars had a 2.88 axle and your 83 should have a 3.07
Reply With Quote
  #8  
Old 03-13-2021, 03:53 AM
Registered User
 
Join Date: Aug 2019
Posts: 949
Easy to tell which speedo you have by looking at where the 3 dots are:

3 dots at 77mph - 2.88 speedo

3 dots at 72mph - 3.07 speedo
Reply With Quote
  #9  
Old 03-13-2021, 09:25 AM
Registered User
 
Join Date: Jun 2006
Posts: 320
Quote:
Originally Posted by christuna View Post
Easy to tell which speedo you have by looking at where the 3 dots are:

3 dots at 77mph - 2.88 speedo

3 dots at 72mph - 3.07 speedo
Oh, you good people make me laugh and I appreciate it!
After decades of working on 617s/W123s, I *still* learn things...

See the attached picture of the original speedometer from a 1985 300D.
Attached Thumbnails
Speedometer registers 5mph fast-picture.jpg  
Reply With Quote
  #10  
Old 03-13-2021, 09:33 AM
tyl604's Avatar
Registered User
 
Join Date: Feb 2008
Location: Atlanta, GA
Posts: 3,640
Yep, love this forum. Who knew? I am headed out to look at my speedo in the '81 300SD.
Reply With Quote
  #11  
Old 03-16-2021, 03:43 PM
Registered User
 
Join Date: Sep 2012
Location: Wilmington, NC by the Atlantic ocean
Posts: 2,530
I don't know where you're located but most major towns will have a speedometer shop - in the Detroit area it's Bob's Speedometers. They'll have some kind of chassis dyno so they can roll the car up and do a speed correction. Generally they'll make a small speed correction box to go between the trans and the speedo cable - problem fixed. At the worst they'll make you a correction table to post near the speedo but I've only seen that happen once at Bob's. BTW - when I worked at the GM Proving Grounds all of the test vehicles had that correction chart stuck to the speedo so us test drivers could drive at the actual speeds for the test cycle and not the indicated speed so they KNEW their speedos were off!

Dan
Reply With Quote
  #12  
Old 03-17-2021, 01:24 AM
Banned
 
Join Date: Nov 2020
Posts: 188
Quote:
Originally Posted by christuna View Post
3 dots at 77mph - 2.88 speedo

It depends if the car is a CA model with the 722.4 or Fed model with 722.3 with 1.48 or 1.44 3rd ratio
I have two 2.88 speedos, one with three dots at 74mph other at 77.
Reply With Quote
  #13  
Old 03-17-2021, 11:29 AM
Registered User
 
Join Date: Aug 2019
Posts: 949
Quote:
Originally Posted by Felching View Post
It depends if the car is a CA model with the 722.4 or Fed model with 722.3 with 1.48 or 1.44 3rd ratio
I have two 2.88 speedos, one with three dots at 74mph other at 77.
Good point but the 722.4 was only installed on CA models and only in 1985 so it's a rare speedo but at least we know that it has 3 dots at 74
Reply With Quote
  #14  
Old 03-17-2021, 01:58 PM
Registered User
 
Join Date: Jun 2006
Posts: 320
Quote:
Originally Posted by christuna View Post
...the 722.4 was only installed on CA models and only in 1985 so it's a rare speedo but at least we know that it has 3 dots at 74
To be clear: My above referenced "1985 300D" is a CA model and indeed, has the factory installed 722.4XY.
Reply With Quote
  #15  
Old 03-18-2021, 07:46 PM
Registered User
 
Join Date: Dec 2006
Posts: 3,941
I know this sounds weird, but the speedometer, trip odometer and the odometer are all separate instruments, geared off the one speedometer cable. If you've verified that the trip and regular odo's have the correct reading, then the instrument is correct for the car, and well matched to the tires and diff. That means that the only problem is that the speedometer is reading low. That can be easily adjusted by pulling the needle and repositioning it slightly. Before you begin, use a short length of speedometer cable to drive the speedometer with an electric drill. Not the speed reading. Then just adjust the needle so that it reads 5mph faster.

Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not 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 On
Trackbacks are On
Pingbacks are On
Refbacks are On




All times are GMT -4. The time now is 03:11 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2024 Pelican Parts, LLC - Posts may be archived for display on the Peach Parts or Pelican Parts Website -    DMCA Registered Agent Contact Page