My speedometer is possesed!

[magking1971]

It started a few months back but driving along and it will start bouncing around like wipers on high, It only starts when I get above 40mph though.
Any ideas what could be going on?

 

[gandalf]

It started a few months back but driving along and it will start bouncing around like wipers on high, It only starts when I get above 40mph though.
Any ideas what could be going on?

I'm going to guess that you have a manual transmission. Otherwise, with an automatic, you would also be complaining about being in limp mode.

My '92 has a sensor on the rear differential which talks with the speedometer, and the TCM if you have an E4OD. When that sensor goes out the speedo starts doing weird things, and the E4OD goes into limp mode because it's receiving an out of parameter reading. As I recall the sensor is on the front side of the differential, the upper portion. Its easy to replace.

 

[icanfixall]

I believe 92 and up trucks had an electronic speedometer run by a sensor in the top of the differential. Below that year they were still a cable driven speedometer. Now you have two distinct trucks in your sig so it would be helpful to know what truck your refering to so we can better help you. WAG is not going to help but its something to know. I kind of feel like Ken does and your talking about the 94 in the signature and its a standard trans. But its a guess none the less.

 

[Ruger_556]

If it's a cable drive it can come loose of the clamp under the floor pan and do all kinds of interesting things...

 

[theguruat12]

If it's your '84, it's 99% one of two things. I have had this happen twice. The first was a worn-out DRIVE gear in the transfer case (or tranny if it's a 2x4), the second was a worn out DRIVEN gear on the end of the cable that connects it to the drive gear. Drive was something like $25, driven was $9. Extremely easy fixes.

Again, that's if it's your '84.

 

[magking1971]

Whoops, Yah it is my 93 (I put wrong year in my sig) and is the E4OD
It is not in limp mode but the speedo is just flipping out more and more.
What is the part called?

 

[jay_t]

My was bouncing only around 65. I replaced the sensor but not the plug on the end of the wires that connect to it. It settled down pretty much, now it happens only from time to time at 65. The next thing for me is to swap the connector out.

 

[pedro_8149]

my 92' does the same thing when it gets upwards of 50mph+ it starts flickering erratically. I do not have any limp mode issues, ive replaced the sensor, checked the wires for breakage. and still does the bounce around all over. im stumped where to go look.

 

[magking1971]

$21.03 And I have a new speed sensor. Now to install and see what happens.

 

[pedro_8149]

Did it help any? Ive tried 3 differnt ones and no luck yet

 

[BigRigTech]

I have the same issue with my 92, not as severe with the 1995 Powerstroke wiring now in the truck but still there. I', going to replace the wiring from the firewall to the diff sensor and that should cure it. The sensor is new already.

 

[magking1971]

I finally got it changed during lunch at work and drove home last night, works perfect!
Thanks for all the help!