Speedometer information.
 

Results from speedo survey.

The number we are interested in.

 

Speedo Number
MPH/KPH
Screw/Push cable connector
Chassis numbers *
Description.
500
KPH
Push on
From 24ZCH000 001 Onwards
Late KPH Speedo
510
KPH
Screw on
Up to 24ZBH200 000
Early KPH Speedo
805
MPH
Push on
From 24ZCH000 001 Onwards
Late MPH Speedo
820
MPH
Screw on
Up to 24ZBH200 000
Early MPH Speedo
1000
KPH
Push on
Syncro Speedo
1600
MPH
Push on
Syncro Speedo

* Note, chassis numbers are shown 24, this is, as you are probably aware for a pick up or crew cab, the same applies for other models, i.e. starting 25.

.
As found in the Bentley manual on page 90.30

Quote:
The number printed on the speedometer face plate below the word MPH shows the number of revolutions required by the speedo cable multiplied by 100 to travel a distance of 1/100th of a mile (52 feet, 9 inch)


Some thing else interesting that the book says is .

Paraphrased.
Quote:
speedo's after may '83 have to read higher than is actually being driven.


This is an american book though, not sure about the regs for european vehicles.

Speedo's with european calibration installed '84 to '85 have a basic calibration of +6.2 MPH with a (+) 5% of the actual speed being driven.
Example given as.
50MPH actual speed.
+ Basic tolerance 6.2 MPH
+ 5% of actual speed
is. 58.7 MPH maximum that can be indicated.

Speedo's with FMVSS (Federal motor vehicle. something or other) started in december '84 have a tolerance of +3 MPH.
so.
30MPH actual speed.
+ tolerance of 3 MPH
is. 33 MPH.

So, basically what that is saying is that your speedo will always over read. I have checked this personally with GPS and my personal speedo was found to be over reading by 4mph. Others too have checked and found theirs to be the same.

There you go, all the nerdy stuff you need to know about speedo's (not swimming trunks!)

Compiled with help from members of the brick-yard and club80-90 forums. Special thanks to Mark W.

 
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