Mechanical Repairs & Troubleshooting On Diesel Engines, School Buses and Related Operating Systems.
Monday, June 04, 2012
Allison Automatic Transmission Retrieving Codes
The Allison Automatic Electronic Transmission offers a quick method to retrieve trans codes without requiring the Pro-Link reader. This is for older models before Allison required shops to have the DOC software to have any hope finding out what the fault is.
The video above is all about a preset code which in this case is losing the "output speed sensor" signal to the Trans ECU. I unplugged the sensor connector and once you try to move forward the transmission defaults into 1st gear. Without an output speed signal the ECU does not know where the transmission output speed is at... so it goes into this mode to protect the transmission because of the programming set up by Allison.
The output speed sensor can be checked out with an ohm meter which averages around 350 ohms depending on ambient temperature. Of course the wiring and connections is a step that should not be ignored. Any kind of resistance in the 30 foot harness running to the driver's cab will give a false signal. Opens and shorts are possible as well since the wiring is exposed to the environment. CHECK OUT THESE PREVIOUS POSTS ON THE ALLISON 3000 SERIES AUTOMATIC TRANSMISSION
Last August I purchased a Bluebird AARE with a 8.3 300 Cummins and a MD3060R trans. What is the best way to determine the type of fluid in the trans? What is in there now is fairly clear with a tint of pink. I am fairly new to diesel mechanical but have 50 years automotive experience. Also this bus has 3 80k under seat heaters one 90k front heater and 2 45k drivers seat heaters. Since you operate in a colder climate is this overkill and how many could I remove and still be warm enough.
ReplyDeleteI am converting a Blue Bird AARE to
ReplyDeletemotorhome. It has a MD3060R trans that has sixth gear locked out so it is only using 5 gears. Engine speed is 1800 at 60mph, if I have sixth gear opened up it will drop rpm to 1600, what are your recommendations?
Allen
I have a 1998 MD3060 trans in a Dutch Star motorhome and I am having trouble with the exhaust brake. When it is switched on and I press on the gas pedel it use to disengage the exhaust brake but not anymore. All outher function of exhaust brake works fine,
ReplyDeleteThanks for any help
Ken
Allen,
ReplyDeleteI would keep the 1800 rpm 5 speed. That's a good combination.
Use Dexron IV in your trans.
Ken,
ReplyDeleteThe throttle has to send a signal to the exhaust brake indicating it's position. I'm guessing there's a switch at the pedal linkage to do the job. Make sure there is a circuit there and the switch is operating normally.
Ken,
ReplyDeleteIf you have an air throttle there will be an air switch in the rear engine control box. It turns off the exhaust brake when accelerating (has an air line running to it) but has to make contact to complete the circuit with throttle off. It used to fail on our buses regularily.
Ken,
ReplyDeleteI'm sorry I missed your comment about having a 40 ft throttle cable. I've never seen that as an option (on a school bus anyways).
There has to be some kind of on off switch to send a signal to the exhaust brake. Having an allison electronic transmission which uses the TPS means you need to check the trans. V.I.M (vehicle interface module) this is the interface between the trans. ECU and the engine controls.
There you will find relays and fuses to run the high idle, exhaust brake and anything else that requires a signal from the transmission side (i.e. throttle position, shift range etc.)
Do a search on my blog for "vehicle interface module"
or "VIM" for some background info and location.
John, not sure if my question was posted correctly. 2005 Allison 3000trv in Freightliner M2 cat 300, no codes from trans or eng. New batteries, at 3rd gear shift eng flares problem recurs even after adapts are reset. Sources suggest tone wheel, damaged drum "bumpS", speed sensor, wiring. What would you check first? Thanks
ReplyDeleteI have a 2005 Freightliner M2 with allison 3000 trv with 84K miles. The engine is flaring at the 3rd gear upshift. Shop resets adapts but then problem re-occurs. DOC shows no problems with trans, no codes on engine. Several sources offer damaged tone wheel on output, damaged converter "bumps", erratic speed sensors/wiring from trans to TCM. I would like them to start with the most frequent source of problem. Where would you look initially.
ReplyDeleteJohn, I have a 2001 FL60 with a 3126 cat and an MD3060P six speed automatic. A few days a go the truck felt as if it was skipping 2nd gear, it would shift out of 1st, then slow down then hit 3rd gear and upshift correctly though the rest of the gears. Then it stopped for a few days. I took it to a mechanic and he said there were no codes on the engine, He drove it, but he thought it was starving for fuel and recommended changing the filters. Today it started skipping 2nd again. It seems if I step on the accelerator hard it will shift correctly. I have changed the transmission fluid and filters and the fuel filters. What would you suggest I do next. Do you think this is transmission or engine? There are no codes appearing on the transmission push button display. Any suggestions would be greatly appreciated.
ReplyDeletehow do you lock out 6th gear on a MD3060P?
ReplyDeleteHow do you lock out 6th gear on MD3060P?
ReplyDelete