BAC Forum

General Boards => Technical Support => Topic started by: David T. Richelderfer on July 15, 2020, 03:45:00 PM

Title: Allison 4000 blinking gear selection
Post by: David T. Richelderfer on July 15, 2020, 03:45:00 PM

I release the parking brake and hit the D button.  The pad shows me a blinking 6 for the gear range of 6 forward gears and the transmission does not engage.  I hit the N button and get a solid N, then hit the D button again.  The D stays on (doesn't blink), the transmission engages and off we go.  What's going on?  What is the blinking 6 telling me?  I am not finding this condition in the Allison troubleshooting manual.

Title: Re: Allison 4000 blinking gear selection
Post by: Gerald Farris on July 15, 2020, 04:39:57 PM

David,
What was the engine RPMs when you tried to shift into drive? Excess engine RPMs will give you that condition.

Gerald

Title: Re: Allison 4000 blinking gear selection
Post by: Mike Shumack on July 15, 2020, 04:51:21 PM

See if there are any trouble codes stored. Do you have a "Check Trans" warning light on your dash (and if so, does the light work)?

Title: Re: Allison 4000 blinking gear selection
Post by: Bill Lampkin on July 15, 2020, 04:52:39 PM

Our idle speed is right at 700 rpm, for reference; no blinking lights.

Title: Re: Allison 4000 blinking gear selection
Post by: David T. Richelderfer on July 15, 2020, 06:36:46 PM

It happened twice on the drive to Hermiston, Oregon from Yuma, Arizona.  I think the first time I had started the engine and set the idle up to about 900 RPMs to get the air built up faster after dry camping overnight.  I don't remember if I reduced the idle before pushing the D button.  It would be irregular for me to not press and hold the foot brake before de-actuating the parking brake and pressing the D button.  Pressing the foot brake automatically returns the engine to idle speed.  So... I don't know for sure if the engine was at its normal idle speed of about 700 RPMs.  The second time we had to stop in line on US395 South of Burns Junction for road crew maintenance.  I think I shut down the engine because the pilot-car had to return from the other end of the one-way traffic section... about 10-15 minutes.  I started the engine, de-actuated the parking brake and pushed the D button and a 6 flashed, then pushed the N button, then again pushed the D button and a 6 flashed again, then pushed the N button, then pushed the D button again... and off we went.  I am pretty sure the engine was at normal idle speed this time.

I do not remember seeing any dash lights on but I don't remember looking for any either.  Many of my dash lights are hidden behind the upper curve of the steering wheel... so unless I lean to one side I will not see most of those dash lights.

Title: Re: Allison 4000 blinking gear selection
Post by: Eric Maclean on July 16, 2020, 03:12:03 AM

David
I have to agree with Gerald I believe what you're experiencing is a shift inhibit which can be caused by many things including too high an idle RPM.
Check in the coach assist I just gave Steve the Allison 4000 troubleshooting manual.
I also have the mechanic tips guide if you PM me your email address I'll send you a copy.
Eric