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Hi everyone,
Sense I'm working @ a Dodge dealer as a technician, I checked out this =
issue about tire sizes and speedometer readings.
Here is what Chrysler is writing on there MDS II computer.
"1997 and older Dakota.
The instrument cluster circuitry calculates the proper gauge pointer =
position based upon a vehicle speed message received from the Powertrain =
Control Module (PCM) on the Chrysler Collision Detection (CCD) data bus.
The PCM uses an input from the Vehicle Speed Sensor (VSS) and internal =
programming to decide what vehicle speed message is required. The PCM =
then sends the proper message to the instrument cluster on the CCD data =
bus.
The VSS is a hall-effect sensor that is installed in the transmission =
(two-wheel drive) or transfer case (four-wheel drive), and is driven by =
the output shaft through a speedometer pinion gear. Incorrect tire size, =
incorrect axle ratio, a faulty or incorrect speedometer pinion gear, or =
a faulty VSS can each result in inaccurate speedometer readings."
In other words, on -97 and older you can change the gear in the tranny =
to compensate for bigger or smaller tires. We can NOT calibrate =
speedometer with DRB III.
1998 and newer Dakota.
The instrument cluster circuitry calculates the proper gauge pointer =
position based upon a vehicle speed message received from the Powertrain =
Control Module (PCM) on the Chrysler Collision Detection (CCD) data bus.
The PCM uses a speed pulse input received from the Controller Anti-lock =
Brake (CAB) and internal programming to decide what vehicle speed and =
distance message are required. The PCM then sends the proper message to =
the instrument cluster circuitry on the CCD data bus. The CAB uses an =
input from the rear wheel speed sensor and internal programming, which =
includes a programmable pinion factor to compensate for different axle =
gear ratios and tire sizes, to determine what speed pulse output is =
required. The CAB then sends the proper speed pulse to the PCM on a hard =
wired circuit.
In other words, there is no tranny gear to replace on newer trucks. And =
with the DRB III you can only program the computer for 2 different tire =
sizes and I think 3 different axle ratio.=20
By the way I'm new to this list. I moved to the states last year from =
Sweden, and I really like it here.
I'm waiting for my new -99 Dakota R/T 5,9 Black CC Fully loaded. =
Hopefully I get it before this week is over.
The Swede/
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<META content=3Dtext/html;charset=3Diso-8859-1 =
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<BODY bgColor=3D#ffffff>
<DIV><FONT color=3D#000000 size=3D2>Hi everyone,</FONT></DIV>
<DIV><FONT color=3D#000000 size=3D2></FONT> </DIV>
<DIV><FONT size=3D2><FONT color=3D#000000>Sense </FONT>I'm working @ a =
Dodge dealer=20
as a technician, I checked out this issue about tire sizes and =
speedometer=20
readings.</FONT></DIV>
<DIV><FONT size=3D2>Here is what Chrysler is writing on there MDS II=20
computer.</FONT></DIV>
<DIV><FONT size=3D2><STRONG></STRONG></FONT> </DIV>
<DIV><FONT size=3D2><STRONG>"1997 and older=20
Dakota.</STRONG></FONT></EM></DIV>
<DIV><FONT size=3D2>The instrument cluster circuitry calculates the =
proper=20
gauge pointer position based upon a vehicle speed message received from =
the=20
Powertrain Control Module (PCM) on the Chrysler Collision Detection =
(CCD) data=20
bus.</FONT></EM></DIV>
<DIV><FONT size=3D2></FONT></EM> </DIV>
<DIV><FONT size=3D2>The PCM uses an input from the Vehicle Speed =
Sensor (VSS)=20
and internal programming to decide what vehicle speed message is =
required. The=20
PCM then sends the proper message to the instrument cluster on the CCD =
data=20
bus.</FONT></EM></DIV>
<DIV><FONT size=3D2></FONT></EM> </DIV>
<DIV><FONT size=3D2>The VSS is a hall-effect sensor that is =
installed in the=20
transmission (two-wheel drive) or transfer case (four-wheel drive), and =
is=20
driven by the output shaft through a speedometer pinion gear. Incorrect =
tire=20
size, incorrect axle ratio, a faulty or incorrect speedometer pinion =
gear, or a=20
faulty VSS can each result in inaccurate speedometer=20
readings."</EM></FONT></DIV>
<DIV><FONT size=3D2></FONT> </DIV>
<DIV><FONT size=3D2>In other words, on -97 and older you can change the =
gear in=20
the tranny to compensate for bigger or smaller tires. We can NOT =
calibrate=20
speedometer with DRB III.</FONT></DIV>
<DIV><FONT size=3D2></FONT> </DIV>
<DIV><FONT size=3D2><STRONG>1998 and newer =
Dakota.</EM></STRONG></FONT></DIV>
<DIV><FONT size=3D2></FONT>
<DIV><FONT size=3D2>The instrument cluster circuitry calculates the =
proper=20
gauge pointer position based upon a vehicle speed message received from =
the=20
Powertrain Control Module (PCM) on the Chrysler Collision Detection =
(CCD) data=20
bus.</EM></FONT></DIV>
<DIV><FONT size=3D2></FONT></EM> </DIV>
<DIV><FONT size=3D2>The PCM uses a speed pulse input received from =
the=20
Controller Anti-lock Brake (CAB) and internal programming to decide what =
vehicle=20
speed and distance message are required. The PCM then sends the proper =
message=20
to the instrument cluster circuitry on the CCD data bus. The CAB uses an =
input=20
from the rear wheel speed sensor and internal programming, which =
includes a=20
programmable pinion factor to compensate for different axle gear ratios =
and tire=20
sizes, to determine what speed pulse output is required. The CAB then =
sends the=20
proper speed pulse to the PCM on a hard wired circuit.</FONT></EM></DIV>
<DIV><FONT size=3D2></FONT></EM> </DIV>
<DIV><FONT size=3D2>In other words, there is no tranny gear to replace =
on newer=20
trucks. And with the DRB III you can only program the computer for 2 =
different=20
tire sizes and I think 3 different axle ratio. </FONT></DIV>
<DIV><FONT size=3D2></FONT> </DIV>
<DIV><FONT size=3D2>By the way I'm new to this list. I moved to the =
states last=20
year from Sweden, and I really like it here.</FONT></DIV>
<DIV><FONT size=3D2>I'm waiting for my new -99 Dakota R/T 5,9 Black CC =
Fully=20
loaded. Hopefully I get it before this week is over.</FONT></DIV>
<DIV><FONT size=3D2></FONT> </DIV>
<DIV><FONT size=3D2>The Swede/</FONT></DIV>
<DIV><FONT size=3D2></FONT> </DIV></DIV>
<DIV><FONT size=3D2></FONT> </DIV></BODY></HTML>
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