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For about 600 miles I had erratic analog speedometer operation (wrong speed indicated, then needle waived nearly continuously, then pointer feel off shaft). At the time the needle started waiving the vehicle speed function on the Magnum Intellidrive registers 0. The cruse control also stopped working. No apparent conductor breaks found so far on the Speedo sense wire. Has anyone else been through this and knows of the solution? Everything else appears to still work normally. Thanks in advance!
v/r,

Taylor Hudson
1998 Serengeti Sahara (4060), 3126 CAT (300 hp), Allison 3060W
acquired 2018, 24K miles

Following.
(My speedometer needle has been slightly pulsating for the last 100,000 miles).

Is your transmission shifting normally?

One possibility is the output speed sensor. From what I understand, the input and output speed sensors are the same and if you swap them and your speedometer works, you'll know the output speed sensor is bad.

https://www.scannerdanner.com/rv-mainte ... ssion.html

Transmission is shifting normally. Replacing the output shaft speed sensor as a try.

Last year I experienced what sounds as quite similar symptoms. My trusted mechanic found the problem came from a poor electrical connection inside the engine bay on the forward wall with his multi-meter I don't recall what the part was called. He cut off the old connection end and replaced it with a new. The speedo and the cruise control have worked fine since.
Good luck,
Glenn
1997 Safari Sahara
3126 Cat, Allison trans