Info for a speedometer bounce

[efmoyer]

I'm writing this just to share my experience with this problem and hopefully help someone else that might have a similar problem

Problem:
96 Explorer: Speedometer slowly gets the bounce. First noticed it in higher gears shifting back and forth. After awhile the bounce gets worse, then transmission isn't sure when to shift. (Since the computer uses the speed sensor to know how fast the truck is moving) Sometimes stays in higher gear at a dead stop. Eventually, the speedometer does hardly anything and transmission has no clue what to do, pretty much undrivable, unless you shift manually and stay away from the highways.

Fix:
1. Started out by changing the speed sensor. (no change)
2. Pulled speed sensor out of transfer case leaving wires attached, removed plastic gear from sensor and attached cordless drill to the shaft and ran the drill while the ignition is on. (NOT STARTED) Found that the speedometer worked nice and smooth. That eliminated the console and wiring. Only 1 thing left.
3. Changed gear in the transfer case that drives the speed sensor. (Change both plastic gears right away.)

Runs like a top.

 

[Glacier991]

Great POST ! Thank you so much for sharing that. People who use search, and who have a similar problem can learn from your well done work (that is how a problem ought to be atacked in my view... logically.... Anyway GOOD JOB! and Thanks!

 

[Ray Lobato]

Good write up! Thanks for sharing the info.

 

[imblue]

3. Changed gear in the transfer case that drives the speed sensor. (Change both plastic gears right away.)

Runs like a top.

You changed the gear in the transfer case too?
The one on the speed sensor seems easy enough, but how did you change the (brass?) one inside the case?

Thanks,
Clint

 

[imblue]

Okay....i went to the dealer twice today to get the plastic gear that goes on the end of the speed sensor.
They had no idea what to look for. They couldn't find it in their catalogues or their computers.



The guy asked me for my VIN and tire size so he could try to figure out what to order.

Is there a part number for this that i could give to the guy?

TIA,
Clint

 

[imblue]

Never mind....

This was over in the "List of Useful Threads"....

New Teeth = (Current Teeth x Speedo Reading)/Actual Speed.

Manual Transmissions and all 4x4s:

16 tooth wine(C0DZ-A)
17 tooth white(C3DZ-C)
18 tooth yellow(C0DD-B)
19 tooth pink(C0DZ-B)
20 tooth black(C1DZ-A)
21 tooth red(C4OZ-A)

2WD Automatic Transmissions:

16 tooth blue(D0AZ-A)
17 tooth green(C7SZ-A)
18 tooth gray(C7SZ-B)
19 tooth tan(C7VY-A)
20 tooth orange(C8SZ-B)
21 tooth purple(D0OZ-B)

 

[410Fortune]

Dont let the colors fool you they are the same unit I wish they made 22 teeth hahaha my speedo is close but not perfect.

I have had 3 speed sensors, 3 speedo cables, umpteen gears (I have a collection of these suckers) installed on my truck over the years. The bouncy speedo needle is usually either a bad cable, a loose speed sensor/impoperly mounted gear, or a bad gear.

The more teeth you have the more it will bounce and the less accurate it is at slower speeds.

 

[imblue]

Thanks for the add'l info 410.

Well, I swapped-out the VSS - no change.
Then I replaced the driven gear (yellow, 18 teeth) - no change.
Next step is to change the drive gear inside the transfer case.
But the Haynes manual doesn't offer much help there.
I'm off to search the archives.

Clint (still feelin blue)