Preempted sorry if this is in the wrong place but my truck has stumped me a little bit of history they came on about three days ago and it has no codes and it just randomly on my way home the abs and park brake light came on and the spedo bounced from actual road speed down ten to twenty mph then back up then down so on and so forth the problem isnt as noticable under thirty and its off until the truck gets on the road I have reset the computer by removing the negative cables then replaced them an hour later no luck so I removed them again and replaced the rear wheel speed sensor hooked up the cables and still no luck.the reason I put this hear is because for our trucks i can by a sensor that goes into the transmission from the parts store meaning ther is two sensor but my chrysler corporation repair manual says I only have one thought and ideas? if ther is no sensor in the tranny then its down to faulty new sensor, wiring or abs computer (most likey) but pcm could still be at fault just a FYI each time the batterys were disconected and reconected I checked for codes a total of three times and have received nothing

Preempted sorry if this is in the wrong place but my truck has stumped me a little bit of history they came on about three days ago and it has no codes and it just randomly on my way home the abs and park brake light came on and the spedo bounced from actual road speed down ten to twenty mph then back up then down so on and so forth the problem isnt as noticable under thirty and its off until the truck gets on the road

Rear speed sensor is bad...

I have reset the computer by removing the negative cables then replaced them an hour later no luck

Do it again now because disconnecting the batteries wipes out the APPS calibration so now do a APPS calibrate. Disconnecting the batteries will NOT reset or erase any error codes!

so I removed them again and replaced the rear wheel speed sensor hooked up the cables and still no luck.

the reason I put this hear is because for our trucks i can by a sensor that goes into the transmission from the parts store meaning ther is two sensor but my chrysler corporation repair manual says I only have one thought and ideas?

The rear speed sensor controls the speedometer and odometer. But the speed sensor in transmission I think is for shift control more so.

if ther is no sensor in the tranny then its down to faulty new sensor, wiring or abs computer (most likey) but pcm could still be at fault just a FYI each time the batterys were disconected and reconected I checked for codes a total of three times and have received nothing

So that means one of the front sensors is bad too...

Also ABS/BRAKE light will not reset till the vehicle is moving. So if the problem is truely corrected the lights will go off after a short distance.

Rear end speed sensor is for the speedometer so if the speedo is wigging out then the rear sensor is bad. But if the speedometer is smooth and correct then one of the front 2 ABS speed sensors is failed.

Front axle sensor location on the bearing. (4WD drive)

Thanks much for staigtening that out so I got a bad new rear wheel sensor? and I only have rwal on my truck so I only have that one sensor on the pumpkin that I replaced.Now if you correct the problem it will go off automaticly correct? what is the best way to test that sensor or possibly the cab because the output shaft sensor(sensor I was looking for and wondering about) which is only in 4 speed autos goes straight to the pcm according to wiring diagrams so that shouldnt even throw the abs light correct? I hope its not another comp prob who needs abs anyway

I think you misunderstood Mike a bit, The front wheels each have an ABS sensor, the rear differential has one on top of the diff housing. Take it out and see if it has a lot of metal on it as it is magnetized and will pick up the metal debris from the rear end oil and this will make it erratic. I have found in most cases that if it is erratic the sensor is still good and is just full of metal particles, if it has a lot of metal on it I would also suggest a rear diff oil change and inspection for potential issues. Once the problem is corrected the ABS light will go out by itself after the computer sees all the signals it likes after it is rolling, sometimes it takes longer than other times to reset itself. Edit I missed the part where you already replaced the rear sensor, So I would say its a front wheel sensor issue.

Thanks much for staigtening that out so I got a bad new rear wheel sensor? and I only have rwal on my truck so I only have that one sensor on the pumpkin that I replaced.

Now if you correct the problem it will go off automaticly correct? what is the best way to test that sensor or possibly the cab because the output shaft sensor(sensor I was looking for and wondering about) which is only in 4 speed autos goes straight to the pcm according to wiring diagrams so that shouldnt even throw the abs light correct? I hope its not another comp prob who needs abs anyway

Ok if you got RWAL then its this way...

But still if you replace the sensor and roll the vehicle the ABS module will clear the light on its own...

Thanks much for the help guys and wild and free Im sorry but I dont have front wheel sensors since I only have rear abs and so far all is pointing at the C.A.B. controller thanks much its greatly apprechiated and if you got any tips let me know because it now looks like this two digit repair just turned to a tripple digit repair or more

Did the old sensor have any metal filings on it when you pulled it out or damaged on the tip in any way?Do you have any unusual noise from the rear end? Just trying to rule out physical mechanical failures before jumping into the eletronics any deeper.

The old one came out in pieces so I honestly cant say though I will take the new one out tomorow and examine it because I had to drill part of it out I had the diff cover off a cpl days ago and for 280,000 I'd say you cant ask for much more from a rear end with that kinda usage good even wear on the ring gear and everything is nice tight and noise free on the flip side this is the second time I changed the oil this year soley because I do it every spring as well as tranny and tcase now everytime I've changed for the past two years it still has that gold color though a little blacker understandably no weird smells and my magnets are relativly clean(fyi its a "no slip" or limited slip option rear end) dk exactly how it works but this spring for the first time it was solid black and a little thick also the magnet had metal shavings and 3 solid chunks of metal that were a lil smaller than a piece of pea gravel kinda got freaked out pulled the diff out and kinda went through it and found no damage on the pinion or ring gear or tone ring the bearing looked good and the rear end speced out there is a clutch pak in there that is part of my spiders that looked worn but usable and the spiders appeared good so I put her back in and wen I had the cover off a cpl days ago the fluid looked brand new and the end wore in well btw I did use gear marking paint to make sure the contact patch was right so I'm not positive but I'd say its not the rear end I will post in the morning as to the condition of the new sensor. Thanks a bunch for all the help that you have provided to this point it is greatly apprechiated

Sensor is clean and clear and appears to be in perfect working order... Any ideas? thanks much in advance all the help is always greatly apprechiated

sensor was clean a couple of days ago and after checing all the wires and computer my only thought was wiring harness till yesterday after I was pulling a 20ft enclosed trailer I decided to look at the sensor again and sure enough little pieces of metal stuck to the sensor. cleaned it put it back in then I could get up to 40-50 before my light would kick on same as what it was doing the day I changed it. was the sensor clean a cpl days later after I replaced it because I cleaned out and changed the diff fluid? now comes the million dollar question if it is the rear end does anyone know wher I could find a good used dana 80 to put in place of that 70 and if not does the 70 require a press or spreader to rebuild? Im pretty sure its just the power lock thats taking a dive... Thanks in advance any thoughts help or comments are always greatly apprechiated

To swap to a dana 80 you will need to shorten the drive line about 1-1.5 inches as the housing is larger or get a driveline out of a D80 rig, get the longer plates that go under the u-bolts on top of the leaf springs and get the lower u-bolt brakets that go under the axle as the axle tube diameter is bigger on the D80. Other than that it is a bolt in unit. I know all this because on my 02 I did a D80 swap into it a few years ago. I got all the parts off a totalled out pickup for 1000 bucks and resold my D70 for 900 bucks. Not hard to do either. As far as needing a spreader, no, I have rebuilt literally dozens and dozens of Dana diffs and have never used a spreader.

Thanks Wild and Free for that information I just got back from trailering a boat 100 miles to storage and now the spedo is never right I plan to look at the sensor again but would you think the problem is not actually the rear diff? considering when the light is off the rwal always kicked on no matter what even if the tires werent sliping and that was right after I cleaned the sensor...

I am not saying it isn't something else wrong, I was just giving you other ideas to check before throwing expensive electrical parts at it.