Speedo Calibration - new tires
Thread Starter
Joined: May 2006
Posts: 4
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Speedo Calibration - new tires
This is a good one. How does one adjust the speedometer when you change tire sizes? The vehicle in question is a 2003 ram 2500 CTD. I can use a GPS to verify.
John Andres
2006 RAM 2500 CTD
'93 Hummer with a 2003 305hp CTD
John Andres
2006 RAM 2500 CTD
'93 Hummer with a 2003 305hp CTD
Thread Starter
Joined: May 2006
Posts: 4
Likes: 0
RE: Speedo Calibration - new tires
Update on this.
The 2003 drivetrain is going into a Hummer H1 with no provision for ABS. I was told by a service tech that the speedometer is controlled by the engine's PCM, not the ABS module. It can only be adjusted up/down ONE tire size.
SO is it controlled by the PCM (if so, that's a good start) and what about the tire size issue. I hate doing conversion math in my head as I drive.
thanks!
The 2003 drivetrain is going into a Hummer H1 with no provision for ABS. I was told by a service tech that the speedometer is controlled by the engine's PCM, not the ABS module. It can only be adjusted up/down ONE tire size.
SO is it controlled by the PCM (if so, that's a good start) and what about the tire size issue. I hate doing conversion math in my head as I drive.
thanks!
Professional
Joined: May 2006
Posts: 103
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From: Maryland
RE: Speedo Calibration - new tires
im not sure if this will help but i have seen speedo calibrators at http://www.jackit.com/gauges/superli...nsor.htm#dodge. hope that will help
Thread Starter
Joined: May 2006
Posts: 4
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RE: Speedo Calibration - new tires
Update on this.
Thanks for the link, I called tech support there and the tech seemed to think that the ABS computer was involved. Note, a RAM 2003 drivetrain is going into a '93 Hummer H1 without ABS. Ans is ABS necessary for the speedo to work.
I spoke to the service managers at a couple Dodge truck service centers. Neither knew for sure. One said that the ABS wasnt involved, that the ECM/PCM in conjunction with the transmission drove the speedo. I was so happy tearing apart my 2003 Ram CTD, I decided t buy a new '06. I disconnected the ABS connector to the rear diff and drove around the block, the speedo worked (and of course, the ABS light was on). Then I disconnected a connector on the tcase. Speedo still worked. I'll try disconnecting those and the front abs connectors as well. If it still works, Im in ok shape as the speedo isn't getting it's info from the wheel speed sensors. I dont recall if there are more than one electrical conector on the tcase. If they dont use a wheel speed sensor (tone ring), the tcase speed (low or high range) would seem a component to true vehicle speed.
Until I disconnect the front ABS, I really wont know for sure. Im inclined to think that the ABS isn't involved. Then assuming ABS isnt necessary, I wonder whether the TruSpeed unit will in fact work. One service techncian though that you could only adjust the speedo up or down a tire size, for $85 by the way.
Thanks for the link, I called tech support there and the tech seemed to think that the ABS computer was involved. Note, a RAM 2003 drivetrain is going into a '93 Hummer H1 without ABS. Ans is ABS necessary for the speedo to work.
I spoke to the service managers at a couple Dodge truck service centers. Neither knew for sure. One said that the ABS wasnt involved, that the ECM/PCM in conjunction with the transmission drove the speedo. I was so happy tearing apart my 2003 Ram CTD, I decided t buy a new '06. I disconnected the ABS connector to the rear diff and drove around the block, the speedo worked (and of course, the ABS light was on). Then I disconnected a connector on the tcase. Speedo still worked. I'll try disconnecting those and the front abs connectors as well. If it still works, Im in ok shape as the speedo isn't getting it's info from the wheel speed sensors. I dont recall if there are more than one electrical conector on the tcase. If they dont use a wheel speed sensor (tone ring), the tcase speed (low or high range) would seem a component to true vehicle speed.
Until I disconnect the front ABS, I really wont know for sure. Im inclined to think that the ABS isn't involved. Then assuming ABS isnt necessary, I wonder whether the TruSpeed unit will in fact work. One service techncian though that you could only adjust the speedo up or down a tire size, for $85 by the way.
