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by **1991cummins** » Fri Dec 12, 2008 7:54 am

alright guys, some of you might remember that i was saying my speedo didnt work... well i bought another one out of a junk yard. installed it and it worked good for about six feet... but once it got up to speed, past 20 or so, the needle started bouncing and twitching and going wild. and when i floor it for just a second at like 35mph in 5th it jumps up to 70-80mph... its really confused... and idle it twitches a little and if i rev it in nuetral the needle jumps up... so i am confused.

so i assume bad guage, again... tell me this though, it get into december and mornings that are really cold 25*-30*(sorry northern guys, thats probably nothing to yall :lol:

) it reads accurate, very accurate, for long periods of time, every now and again it will twitch again, but only a 2-3 mph twitch, rather than 30-50mph twitch

by **KTA** » Fri Dec 12, 2008 8:09 am

Check your sender down on the transmission. I bet the drive is rounded off.

by **1991cummins** » Fri Dec 12, 2008 8:17 am

huh, yah, thats possible... another thing, the odometer doesn't work... at all...

but then again why would that cause it to read faster than i am going, wouldnt that make it read lower... cause i wil be going 20-30mph in third, and it will jump up to 70/80 sometimes even 90-100 mph...

by **dpuckett** » Fri Dec 12, 2008 3:42 pm

Check your wiring. If that's ok, it's likely your speed sensor, or something grounding/ shorting out along the way.

by **1991cummins** » Fri Dec 12, 2008 3:58 pm

yah, i have done a simple check of the wiring, and disconnected and reconnected my control module above the wheel well... i have another gauge for it, lol... so i could try that to... cause the speed sensor is brand new... i just bought it from auto zone a little while back cause it was cracked...

does anybody know why the cold would have an effect on it... i know it sounds silly, but every single cold morning it works well, and then after school when its hot, it sucks, and spazzes out

It sounds dumb to me, but the temp really does make a difference...

by **1991cummins** » Fri Dec 12, 2008 4:41 pm

checked the sender, still square...

by **PToombs** » Fri Dec 12, 2008 6:13 pm

1991cummins wrote:checked the sender, still square...

I think KTA meant the gear rounded off inside. :lol:

I wonder if the gear on the shaft in the trans is loose? When it's cold it the oil is stiff and it grabs, when it's hot the oil is thin allowing slippage.

by **1991cummins** » Sat Dec 13, 2008 7:47 am

oh... duh haha, well yah, idk... i will try to put in this next speedometer just to make sure its not the guage since i have it laying around, and then if its not that, start checking other things...

by **SChandler** » Sat Dec 27, 2008 10:42 pm

I would try the 90* piece coming off of the side of the transmission. My D250 did the same thing. I checked the wiring, I replaced the sensors, it would work fine for a few months, then it would slowly get worse until it quit completely. I took the 90* piece off (I think Dodge calls it a "speed sensor adapter" or something like that) and plugged the sender straight into the tranny. The speedo worked flawlessly other than reading 1.5x the speed I was actually going. I replaced the 90 and everything worked great. Mine had so much slop in it, the internal gears were barely engaging.

by **1991cummins** » Sat Dec 27, 2008 11:19 pm

huh, ill try that next? any chance that that the PCM is screwing up? and does it make a difference that in all three of the guages and have switched around with the odometer doesnt work...

by **SChandler** » Sun Dec 28, 2008 2:08 pm

The odometer is a separate issue if I remember right. It has some plastic pieces that get old and break, leaving it non-functional. Otherwise, the odometer should track miles based on whatever the speedometer is telling it.

by **1991cummins** » Sun Dec 28, 2008 2:19 pm

huh... well none of them work... so i dont know what to think, and one of the speedos only has 102k on it, so i would assume it's would still be in tact... god, i am fed up with this! grrrr :mad:

does the PCM have anything to do with my speedometer, or does it just run through there for cruise control equipped models? i bet its just grounding out somewhere... that i havent found... im guna go look again... and again

by **dpuckett** » Tue Dec 30, 2008 2:58 pm

1991cummins wrote: the speed sensor is brand new... i just bought it from auto zone a little while back....

There's your problem. I have quit buying anything electrical at parts stores. Have to bite the dealer bullet for this one.

I still say, if it's jumping up to 70-80mph, your sensor is toast.

DP

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