Speedometer and Odometer Not Working Correctly On Allison 545

Forum for both AC and DC electrical components. From engine alternator to dashboard, inverter to batteries, and everything electrical in-between.
Post Reply
Posts: 5
Joined: Sat Jun 11, 2022 6:59 pm

Speedometer and Odometer Not Working Correctly On Allison 545

Post by Tange206 »

Hello freinds,
I have a question pertaining to my 1991 Safari Serengeti which I just bought. The electronic Speedometer and Odometer don't work correctly, when I turn the RV on the speedometer goes from 0 to 15mph without any acceleration or even movement and when I turn the RV off it goes back to 0. The Odometer sometimes spins too fast and sometimes doesn't spin at all.

Shifting feels good through all gears, there is no slipping or jumping of gears. The only problem I can see is that the speedometer and odometer won't work. Also, I think there appears to be a cut sensor of some sort (which might be the transmission temp sensor) off the torque converter.

The transmission is an Allison 545 and it's an electric speedometer. Any thoughts or troubleshooting advice would be greatly appreciated.

537a1f7189d23800702116db2e9909a68a9a0a32-1.jpg (400.71 KiB) Viewed 32 times
537a1f7189d23800702116db2e9909a68a9a0a32-2.jpg (642.79 KiB) Viewed 32 times
Posts: 2
Joined: Fri Mar 18, 2022 11:51 am

Re: Speedometer and Odometer Not Working Correctly On Allison 545

Post by DPRoska »


I'm not sure how much help this is. I own a '91 Safari Sarengeti (Hi Tech) model. My Speedometer was acting up so I investigated and found the sensors, removed them, and did a bit of research.

Mine, off a 4/5 speed Allison is a mechanical sensor, that is coupled with an electric sensor. The mechanical part includes a small sprocket-type wheel that inserts into the transmission and touches a type of flywheel, causing it to spin. The sensor wheel is attached to a small square cam or axel and hence, turns another mechanical interface to create a voltage. I believe the voltage is then sent to a third device, behind the dashboard for regulating a signal to the actual speedometer. The speedometer may have an Oshkosh logo, and not easy to find.

I could send you a photo of the sensor(s), however not seeing how to do this on the safarifriends website.

I tried to rebuild the mechanical side of the sensor(s), and it worked great for a while, until I downloaded an AP to serve as my speedometer, so I removed it from the transmission. One of the places I called, after many hours, wanted $400 to replace the sensor, and so just using the AP for my alternative solution.

The photo you included appears to be a temp sensor, and looks nothing like the speed/odometer sensor(s).

Kind Regards - Doug R.
1991 Safari Serengeti (Hi-Tech), paired with Cummins and Allison Trans
Posts: 391
Joined: Sun Oct 27, 2019 11:34 pm

Re: Speedometer and Odometer Not Working Correctly On Allison 545

Post by TDJohn »

The sensor pictured in the photo with the cut wires is the rpm sensor for tach. Sorry, I don't recall where the speedometer sensor is, possibly on the output shaft of the transmission tail shaft housing?
'95 Serengeti, Cummins C8.3-300
Allison 6spd.
Post Reply