out of the blue the speedometer went crazy. if i am going like 50mph it reads 120mph what would cause that? o ya its in a 2001 ram 1500 5.2

is there a little plastic gear in the tail shaft like other cars. if anyone knows how i can fix this please let me know.

 

Your speedo is controlled electronically. I wouldn't know where to start? I wouldn't think it was a loose wire because then it would drop to zero. Maybe, one of the body control modules that control the gauge cluster is going bad.

 

well i used the power programmer and put is back to stock and that's when is happened and i tried to leave the programmer on to see if it would fix it but is don't. can it be the dash part its self or is there a little gear in the tail shaft of the tranny like a lot of other cars?

 

hold the trip odometer button in for about 5 seconds on the cluster panel as you turn the truck on, then release. Itshould do a cluster testand sweep the dials 25%then 50% then full sweep. It'll let you know if the problem's the gauges or the speed sensor in the rear diff.

 

no gear in your 01.

try this first - press and hold odometer trip meter while you turn the key to on. continue holding in trip meter until it says CHEK. then watch the instrument cluster for a series of test that light up each bulb, then swing the gauges through 3 positions. about 1/4, about 1/2, and then full. the test ends with a possible error display in the odometer. i think this is an adequate test of the cluster itself.

you have 2 speed sensors that provide information to the pcm. one is in the transmission tailhousing (2wd) or transfer case (4wd). the other is in the top of the rear differential. there is considerable debate about which one does what. neither sensor is overly expensive, around $20-25. if $ is not an issue, i'd change the transmission sensor first, and it that doesn't work, then the rear diff sensor. if you have buddy with a similar truck, you could try swapping sensors.
here's a nice application website for a recognized brand, SMP.
http://www.standardbrand.com/web_app...liccatalog.asp

 

ok never mind all the above. while i was typing that you came in with the hypertech info.
question - did you reprogram a different tire size with the hypertech ? it sounds like the pcm has the wrong tire size factor stuck in the pcm. you might try re-programming tire size with hypertech, and putting back in the stock size (about 28" i think).

 

just went out side and tried the odometer button it did a little check thingy and the all the gauges went to about 1/4 then 1/2 and the n all the way up to max on all of them so what does that mean?

 

It means your gauges are fine and not malfunctioning.

check the hypertech for tire size as dhvaughansuggests.The programmer can adjust the speedo for tire size. If you accidentally told it you have smaller tires it'll think the truck is going much faster than it actually is.

What size tire do you currently have? read the info on the tire sidewall to verify. Here's a calculator that can convert it to inches if you need to:
http://www.miata.net/garage/tirecalc.html

If you've got a tire like 245x75x16 it'll tell you in inches what you tire size is, then you can adjust the HT by .25" to match.

if you do all that and still have problems, then worry about the speed sensors.

 

it means the speedometer in the cluster is working fine.
and your problem is either in the pcm programming, or the sensors.

edit. dad-gum, squirrel is quick this morning. beats me to the punch every time.

 

gotta be quick to smash them squirrels.