Tuesday, June 16, 2015

Allison 3000 Automatic Transmission Turbine Sensor Replacement

Allison 3000 Automatic Transmission Turbine Sensor Replacement requires removing the bottom module of the transmission using a transmission jack. The module weighs around 50 pounds so it's much easier to lower it down easily while feeding the harness through the access hole in the transmission housing.

The turbine sensor is internal and is easily replaced once the module is exposed. This code is not very common but it was plain as day when hooked up to Allison DOC software. You can view a graph while road testing and the turbine sensor communication dropped out while on the road. There are 3 sensors on the Allison 3000 models. The engine speed sensor, output speed sensor and turbine sensor.

All these sensors have to be working properly for the transmission to shift properly. They can be tested using an ohm meter. Depending on the ambient temperature the reading should be around 300 ohms. The video gives you an idea on what the module looks like when removed from the main body and where the turbine speed sensor is located.

The 3000 series are very durable and most of the problems were in the wiring. The plastic convoluted loom that the harness is wrapped in is deadly on the wiring insulation. Through time vibration causes the loom to rub on the wiring and eventually expose the copper wire to the atmosphere. Years ago we would run new wiring to a sensor because of the resistance caused by exposure to the elements.

The special wire was twisted and shielded that fixed a lot of communication problems, Using the Pro Link was the first tool available for troubleshooting. Now Allison Doc software is the only way to go. Also I have to give a plug to synthetic transmission oil which in the past I refused to accept because of the price.

Believe me it's well worth the extra cost. Our mechanical failures are non-existent since using synthetic oil. It lasts longer and does not break down in the heat. Our services are 3 years between oil changes. You can't beat that when in our case we're running 77 school buses.

Getting back to our turbine sensor code repair. When removing the module I want to point out that you need to remove the 32 fasteners by hand. The aluminum threads in the housing wear out..... especially the filter housing retaining bolts. It isn't a fun experience heli coiling the threads on these units. We have a Kent Moore tool jig to re-thread the holes which is the only way to do it. I use a speed wrench to remove and replace the bolts.

I hope you enjoy the video and please make a comment and share this post. Cheers!  

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