Speedomter error
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From: Fairview, North Carolina
Speedomter error
I have a 91 Dodge 3/4 Ton w/ 4WD- 3 speed auto (non overdrive)- replaced sending unit and now speedometer runs 12-15 mph slower- took part out and it's identical with old part and dealer says it's correct- suspect its for the OD tranny but no other part listed- any suggestions
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From: Mustang, OK
Re:Speedomter error
Out of curiousity, how much was the sending unit? Did you make sure you rotated the speedo gear housing and bolted it down in the right position? If you look at the gear tooth housing for the speedo, you will notice numbers written on the top, (30-35, 25-30 etc.) there will be a number on the yellow gear tooth that goes into the transfer case (4wd) or tranny (2wd). this will show the number of gear teeth that is present. You should then take the "V" shaped clamp and line the slots up with the numbers. If in the wrong position though, most of the time the speedo wont work at all.
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From: Fairview, North Carolina
Re:Speedomter error
the unit was about $60 bucks- there aren't any teeth as this is an electronic unit that screws into the side of the case- the connection is electronic- my original sending unit went out twice- 89K and 147K i put this one in after living w/ a dead speedometer for about 2 months- it works perfectly just 12-15 mph slow- 50mph is about 64 or so- i took the unit out and back to the dealership who spent a lot of time looking it up but all the numbers matched up- he says they only list one- i think that's the problem (unit for the newer units w/ od) but there aren't any other parts listed- if i could find an aftermarket source i would look into that- thanks for your response<br><br>
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Re:Speedomter error
OkieB,<br>That's what I thought at first, but I personally checked the sensor on FATRACING's truck. It is totally different than the one on my 95. On the NP205 case, there is only a threaded fitting for the sensor to connect to. No numbers or adjustments like on later models. First I thought about the OD/no OD question - but shouldn't make a difference: driveshaft speed is driveshaft speed. The error does seem to indicate that difference margin though. But then another thought - this 91 has 3.08 ratio diffs, not 3.54's. As I understand it, the dealer didn't ask about gear ratio - so how would the pcm know how to translate driveshaft speed to road speed (since adapter is not adjustable)? Must be more than one speedo adapter - despite what dealer says. I tried looking for the adapter aftermarket - and found a couple. Nobody asked about gear ratios. Guess I'll have to drag out the 'scope & check the signal output. BTW - tires are stock size. <br>Thx,<br>-Scott
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From: NorCal
Re:Speedomter error
While the NP205 transfer case doesn't have the traditional speedo pinion adapter, the driven gear threads into the case and might come in different tooth counts to correct the speedometer.<br>My book also shows an adapter between the transfer case driven gear and the speed sensor that looks like it is a reduction gear unit. This would allow precise calibration of the speedo when the final gear ratio and tire size are known.
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Re:Speedomter error
[quote author=ZONE5AB link=board=9;threadid=9893;start=0#95741 date=1043356142]<br>While the NP205 transfer case doesn't have the traditional speedo pinion adapter, the driven gear threads into the case and might come in different tooth counts to correct the speedometer.<br>My book also shows an adapter between the transfer case driven gear and the speed sensor that looks like it is a reduction gear unit. This would allow precise calibration of the speedo when the final gear ratio and tire size are known.<br>[/quote]<br>Thanks for the info. The day I looked at my buddy's truck, it was cold & windy, & the 205 has the usual leaking seal - so wasn't real inclined to get up close & personal with it at the time. Will check into it more closely, hopefully somewhere warmer... ;D<br>Thanks,<br>-Scott
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Re:Speedomter error
Fatracing,
I am a dodge owner but not the dodge expert, however i run a salvage yard for mercedes and bmw, both of which use electric speedometers and similar sensors.
The sensors are basically a looped wire inside a magnetic housing that generates a signal when a toothed wheel passes.
The signal is interpreted by the speedometer itself. Signal can be mis-interpreted if the gap between the toothed wheel and the sensor is too small or great, but other than that it only performs the one duty.
Check to see if your sensor may not be seated correctly, but other than that, i'd bet you have the right part, different problem. Good luck!
-RATCHET-
I am a dodge owner but not the dodge expert, however i run a salvage yard for mercedes and bmw, both of which use electric speedometers and similar sensors.
The sensors are basically a looped wire inside a magnetic housing that generates a signal when a toothed wheel passes.
The signal is interpreted by the speedometer itself. Signal can be mis-interpreted if the gap between the toothed wheel and the sensor is too small or great, but other than that it only performs the one duty.
Check to see if your sensor may not be seated correctly, but other than that, i'd bet you have the right part, different problem. Good luck!
-RATCHET-
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