dieselcarpenter

When I got my truck the speedometer/odo/trip did not function, I crawled under and found that the speed sensor and gear reduction calibrator were loose (bout to fall off) so I tightened it up, fixed right? wrong. I checked the shafts and the speed sensors shaft was round most of the way up. So, put a new one on, fixed right? wrong. I checked to make sure both units work together by spinning them, they seem to, unless its a false positive, works in my hand and not on the truck (tried hand tight, wrench tight and wrench snug). Pulled the cluster and the conections looked good, and the needle is not stuck. The shaft locks into the t-case positivley but I haven't checked to see if the t-case is spinning, could be the wiring, everything I could see looked good, the rest is buried in the truck. Is there a fuse, relay or somthing behind the speedomter itself in the cluster thats bad? My chiltons manual has some wiring diagrams but the speedo is nowhere to be found, They think my model year has a cable are there any better manuals out there? I like the haynes but they dont start the cummins until 94 and up and the chilton has every truck dodge made crammed into one little bookare there any diagrams online? Please help!!!!!!!!!!!!!!!!!!

PS maybe an after market like autometer is an easier choice?

rockfoot

I pulled my speedometer and read out the incoming leads to the where the speedometer was supposed to be plugged in. One pin is ground, one pin is +12vdc and the other pin reads millevolts to ground. I did notice that at about 60 mph, the millivolt (which actually varies with the speed) reading was about 60 millivolts... and varied accordingly. I had alligator clips on the pins and the voltmeter resting on the console between the seats. If you do not have that varible millivolt input from the speed sensor, the speed sensor is not putting out. That could mean that it is bad or it is not spinning or a bad connection.... there is no fuse from the speed sensor to the speedometer. There is a fuse to the +12 vdc to the top pin.... You can also jack up the rear end so you won't have to do this riding down the road....

rlyons

Mine is 2 wheel drive but the gear was loose on the output shaft of the transmission and slipping. I removed the output flange and shimmed the gear tight and have not had a problem since.

rockfoot

Just checked the book (fsm) The top pin is ground, the middle pin is +12vdc and the bottom pin is the input from the speed sensor

dieselcarpenter

Where? on the back of the cluster?

dieselcarpenter

what should the sending wires from the sensor (only two) read?

rockfoot

The wire that ends up at the speedometer from the sensor goes to the bottom wire of the speedometer. If you have you dash bezel off and the plastic cover over the gauges off, there are three screws holding the speedometer in. Remove those three screws and you can pull the speedometer straight out. There will be three pins that plug into the speedometer that are now exposed. The top pin is ground.. the middle pin is +12 vdc and the bottom pin is from the speed sensor. With the rear wheels off the ground and the engine running with the transmission in gear, the speedsensor pin (bottom pin) will indicate a millivolt reading if it is working. The reading is taken between the bottom pin (+) and the top pin (-). As the motor speeds up, the millivolt reading should increase.

dieselcarpenter

Thanks, Ill try it out!

BearKiller

Unless a 4wd is different from a 2wd, you can also remove the drive-head from the transmission and chuck the pin in a drill.

Have someone operate the drill, while you take the readings.

It doesn't take much drill-speed to really make the speedometer climb.

Also, some models require the drill be in REVERSE, while others work forward.

Using the drill can be done without the engine running.

dieselcarpenter

great idea!

gomerpile

well you might also be in the same boat as me just your odo/trip gears are broken. if thats the case if you fix the gears you odo will work but the speedo still wont work.i checked the pins and got current all around. so i installed a tach b/c i couldnt find any speedos in a junkyard and the factory one costs $350 last i checked (11/18/2006). so now i just went and bought a garmin e-trex from wally-world.com for $160 and mounted it on the dash.