Allison Automatic Transmissions Exclusive to School Buses
I was thinking how many Allison automatic transmissions are operating in North American school buses. There must be thousands (probably more)….no other brand that I know of is being used more than Allison.
Automatic transmissions are by far the best drive train component to run in any fleet simply because it takes away the distraction of shifting a manual transmission. The driver just has to push ‘Drive’ and Go.
James Allison started His company in 1915 building the first heavy duty automatic transmission. He also started the Indianapolis 500 Speedway in 1909. Go to the history of Allison Transmissions to get the complete story behind the company.
They accomplished a lot through the years with new technology along with their numerous contributions starting with the First World War.
Using Allison Automatic Transmissions In Our Fleet Operation
We are using the 2000 and 3000 Series automatic transmissions in our fleet and they have done very well through the years. Back in 2005 we started getting MD 3000 electronic transmissions which were controlled by a TCU (transmission control unit).
They were good and the only weakness at the time was the OEM bus wiring which really made things difficult for a while. The first buses we received were not shifting and codes were constantly active.
After working with the dealer we found the transmission wiring from the battery to the TCU had been spliced half way along the frame with regular (unsealed) butt connectors.
This caused mayhem with the operation of the transmission. The corrosion was so bad in the connections that the voltage drop would not let the shifting work properly. There was a discussion between the bus and transmission OEM dealers about who owned the wiring harness that was at fault. Everything worked out in the end and the problem was fixed.
Working Experiences With Allison Transmissions
After the factory wiring problem life was good in the transmission department for a long while until minor little problems popped up with the connections and wiring harness. The WTEC II system that we were working with had a main feed connector into the transmission control module which housed shift solenoids and sensors.
That connector was exposed to the elements and created codes and shifting problems. We found ways to protect that connection from snow and moisture which made a big improvement.
Later the wiring developed resistance problems to the output speed sensors, vehicle speed sensors, turbine speed sensors and other related parts that sent data to the TCU. This caused poor shifting and other faults with the transmission.
We found the best fix was to totally replace the wiring on the suspected circuit front to back. This worked well instead of trying to locate a bad spot in the wire.
We started to stock rolls of coaxial wiring so complete replacement could be accomplished. This wire had the extra shielding wrapped around the wiring so the data signals don’t get affected by outside interference.
Allison Transmissions and Prognostics
The present day Allison transmission offers a really unique software that monitors oil and filter life and tells the driver when service is due. An icon shows up on the dash in the form of a green gear with a wrench.
This light is telling us whether we have to change the oil or the spin on filter. After servicing is done the monitor is reset using the Allison Doc software.
The process starts all over again…..this is a very impressive system and makes maintenance scheduling a breeze. The proper oil has to be used in Allison transmissions for this program to work accurately. At present since we started using the 2000 series models there has been absolutely no mechanical problems.
There was one time the wiring rubbed through externally on the frame which caused shifting hassles but that is the only time I can remember having an issue. On top of oil and filter monitoring is the health monitor that looks at clutch wear and related parts that helps prevent major break downs before they occur.
Allison Prognostics is ingenius and for us fleet guys it brings less maintenance planning and major break downs saving time and money.
Thanks for checking out this post and I hope you got something out of this information. Please comment and share 🙂