Air brakes wont release /trans wont move from neutral

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Air brakes wont release /trans wont move from neutral

June 24, 2020, 02:20:29 pm

Good morning Fortravel GODS, I went to move my coach this morning backed up about 30 foot all ok tried to move forward nothing, backed up 10 foot all ok tried to move forward nothing now air brakes wont release /trans will only go into or show neutral NO codes everything seems normal other then that . What is a good place to start troubleshoot? thanks in advance Tonka

1996 u-270
8.3 cummins
build #4794

Re: Air brakes wont release /trans wont move from neutral

Reply #1 – June 24, 2020, 02:29:06 pm

Parking brake release isn't working. The coach will back up cold with parking brake on but has to be released to move forward.

Re: Air brakes wont release /trans wont move from neutral

Reply #2 – June 24, 2020, 05:00:06 pm

What is your air pressure? If under #60 they won't release.

Re: Air brakes wont release /trans wont move from neutral

Reply #3 – June 24, 2020, 05:20:06 pm

Any audible or visual alarms showing on the dash?

Parking brake not releasing is a mechanical problem with air system. See question above on air pressure.

Transmission not going into gear could be a electronic problem. What is idle rpm? If idle is too high, trans will not go into gear.

Re: Air brakes wont release /trans wont move from neutral

Reply #4 – June 24, 2020, 05:40:45 pm

Build full air pressure and try to release. If no joy, repeat and repeat again. I had a DD-3 can stick at Rocky Mountain NP on my bus. I must have tried at least 50 times when it finally released. Never did that again but I rebuilt it when I got home.

Pierce

Re: Air brakes wont release /trans wont move from neutral

Reply #5 – June 24, 2020, 06:34:54 pm

So air pres at 120 #
HWH green travel light lit no other warnings
Park brake light lit when park brake applied goes off when released (sounds normal) can see pres drop on air gauge
RPM at about 525 at idle
Both N's are lit on allison keypad (looks normal)

Re: Air brakes wont release /trans wont move from neutral

Reply #6 – June 24, 2020, 07:18:47 pm

Quote from: tonka – June 24, 2020, 06:34:54 pm

Both N's are lit on allison keypad (looks normal)

So, nothing happens when you use the keypad? Pushing buttons does nothing at all? I would try pulling the pad connectors and replacing. Same with Allison computer but keypad first. Possible corrosion spray on the connectors before you plug them back in.

If pressure drops, sounds like your brakes are releasing. Don't know about yours but our coach does not need the brakes to be released for the transmission to work normally.

Pierce

Re: Air brakes wont release /trans wont move from neutral

Reply #7 – June 24, 2020, 09:50:43 pm

A '96 U-270 has ADB-1560 not "S" cam drum

https://www.foreforums.com/index.php?action=media;sa=media;in=1701

Mike

Re: Air brakes wont release /trans wont move from neutral

Reply #8 – June 25, 2020, 09:23:13 am

Quote from: Pamela & Mike – June 24, 2020, 09:50:43 pm

A '96 U-270 has ADB-1560 not "S" cam drum

https://www.foreforums.com/index.php?action=media;sa=media;in=1701

Mike

You're right. I forgot about disk brakes, so please tell me this: Can you see the movement of the arm on the slack adjuster?

Re: Air brakes wont release /trans wont move from neutral

Reply #9 – June 25, 2020, 10:21:03 am

You can see the slack adjuster move

Re: Air brakes wont release /trans wont move from neutral

Reply #10 – June 25, 2020, 11:39:27 am

How were you able to back up if shift pad was in neutral? Or did this problem just come up after you moved the coach?

Re: Air brakes wont release /trans wont move from neutral

Reply #11 – June 25, 2020, 11:54:50 am

Quote from: bbeane – June 25, 2020, 10:21:03 am

You can see the slack adjuster move

So, would you say that if it doesn't move and does after a gentle tap with a hammer it's time to service the mechanism?

And just asking out of curiosity, if you try and shift that transmission "in a hurry," will it safety out?

Re: Air brakes wont release /trans wont move from neutral

Reply #12 – June 25, 2020, 12:34:29 pm

So the first time I backed it up and stopped it would not go forward then I moved it back another 10 feet and tried to go forward and nothing now no reverse no forward. Put Trans back in neutral ,brakes locked up Seems like both problems happened at the same time. Am I missing a connection between the 2 systems that prevents brakes to release? Just seems like more then a coincidence! Thanks for all the ideas so far.

Re: Air brakes wont release /trans wont move from neutral

Reply #13 – June 25, 2020, 02:36:49 pm

Quote from: tonka – June 25, 2020, 12:34:29 pm

So the first time I backed it up and stopped it would not go forward then I moved it back another 10 feet and tried to go forward and nothing now no reverse no forward. Put Trans back in neutral ,brakes locked up Seems like both problems happened at the same time. Am I missing a connection between the 2 systems that prevents brakes to release? Just seems like more then a coincidence! Thanks for all the ideas so far.

I would take the problems one at a time and begin with the brakes.

With the wheels securely chocked, and using a helper that didn't have it in for me, I would the operating arm on each side and see if it moves when the parking brake is released, and upon application and release of the service brakes. As long as you're back there make sure the brake lights go on and off.

Re: Air brakes wont release /trans wont move from neutral

Reply #14 – June 25, 2020, 02:48:50 pm

Has this puppy got Maxies on it?

Re: Air brakes wont release /trans wont move from neutral

Reply #15 – June 25, 2020, 04:53:40 pm

Quote from: Old Toolmaker – June 25, 2020, 02:36:49 pm

and using a helper that didn't have it in for me,

I know little off subject, but I canceled my $1,000,000 life insurance policy after 3 attempts.

Re: Air brakes wont release /trans wont move from neutral

Reply #16 – June 25, 2020, 05:25:30 pm

Quote from: turbojack – June 25, 2020, 04:53:40 pm

I know little off subject, but I canceled my $1,000,000 life insurance policy after 3 attempts.

Said the man with the practically fly by wire Foretravel.

Is the transmission in your '97 U295 computer controlled?

Re: Air brakes wont release /trans wont move from neutral

Reply #17 – June 25, 2020, 05:26:55 pm

He listed it in the beginning as

1996 u-270
8.3 cummins
build #4794

Re: Air brakes wont release /trans wont move from neutral

Reply #18 – June 25, 2020, 05:29:27 pm

Tonka

Do you have the owners manual for the transmission? It does have electronic functions that will disable shifting if "Check Transmission" light is illuminated.

Re: Air brakes wont release /trans wont move from neutral

Reply #19 – June 25, 2020, 05:45:26 pm

Here is a copy of the manual I got off their site. Don't know if it your specific transmission or not. It is also for the 3000 series as well.

Re: Air brakes wont release /trans wont move from neutral

Reply #20 – June 25, 2020, 05:47:30 pm

Quote from: NancyS – June 25, 2020, 02:48:50 pm

Has this puppy got Maxies on it?

For those of you younger than a certain age, Maxi Brakes was the trade name for the first of the spring set parking brake. Before that all a truck had was a mechanically set drum brake and wheel chocks. I *think* Maxi Brakes* came on-line in the 1970s.

Article: The Brake System – Adding Spring Brakes – Flxible Owners International

*Not to be confused the Maxie Brakes, an add on lever to help you pull your parking brake valve open.

Re: Air brakes wont release /trans wont move from neutral

Reply #21 – June 25, 2020, 05:53:46 pm

Quote from: master2301 – June 25, 2020, 05:45:26 pm

Here is a copy of the manual I got off their site. Don't know if it your specific transmission or not. It is also for the 3000 series as well.

I love reading manuals.

"NOTE: Turn off the vehicle HIGH IDLE switch, if present, before shifting from N (Neutral) to D (Drive) or R (Reverse). D (Drive) or R (Reverse) will not be attained unless the shift is made with the engine at idle. Also, be aware of other interlocks that would prevent obtaining D (Drive) or R (Reverse). Examples are "wheelchair lift not stored" and "service brakes not applied" (service brake interlock present)."

Re: Air brakes wont release /trans wont move from neutral

Reply #22 – June 25, 2020, 06:00:48 pm

Quote from: Old Toolmaker – June 25, 2020, 05:25:30 pm

Said the man with the practically fly by wire Foretravel.

Is the transmission in your '97 U295 computer controlled?

Yes. That and the AC thermostats are the only things computer controlled in that coach.

Re: Air brakes wont release /trans wont move from neutral

Reply #23 – June 25, 2020, 06:10:53 pm

Maybe there is an air line run to the ECU or it reads a gauge?

Re: Air brakes wont release /trans wont move from neutral

Reply #24 – June 25, 2020, 07:09:58 pm

Quote from: turbojack – June 25, 2020, 06:00:48 pm

Yes. That and the AC thermostats are the only things computer controlled in that coach.

So I just gotta ask, and it's something you would do without thinking: Is there a brake interlock? As in: Do you need to apply the service brake before shifting?

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