Diff lock stuck engaged

[2014pinnacle]

Hi guys I have a 2016 pinnacle with Mack axles the diff lock on the front axle keeps engaging on its own and I can’t get it to turn off? On the front axle on the drivers side at the bottom theirs a plate with 3 bolts and an air fitting going through it is that the diff lock? Can I undo those 3 bolts and pull it out?

 

[mrsmackpaul]

How do you know the diff l9ck is engaged 

 

Does it show up on a dash light or is it something you feel when driving

 

Paul

[2014pinnacle]

The light on the dash comes on and when you hit about mph the interaxle engaged message pops up on the message display screen. I popped the air line off the diff lock and sprayed some pb blaster and smacked the housing around it and the light has gone out and no problems since but I’d like to fix it right I’m sure this issue is going to come back again 

[Nobody454]

the message pops up as a safety reminder when you reach a certain speed. I would check the air solenoid that controls the function, I had several problems with the solenoids. They are all mounted together along the frame. I believe any "air" actuated switch is really electronic, and activates whichever solenoid it needs

 

[Vladislav]

To figure is the diff is currently locked or free I mean physically not judging by the indicating light you need to jack up one of the wheels of the axle and try spinning the wheel by hand. If the diff is free the wheel would turn forcing the prop shaft turning together with it. The tranny must be in neutral though. If the diff is locked the wheel would be locked to the other side wheel and as long as the latter touches the ground and can't spin the whell you check wouldn't go either. The problem is you need the parking brake loose on the tested wheel. So there's a need to loose the slack adjuster on the checked wheel or release the truck's brake having chocks put all over the rest of.

Actually it's important thing to investigate the diff lock operation physically. Because in theory when you see the light on it doesn't really mean the lock is in. And if you don't see the light it also doesn't mean the diff is free. The light switches on by a push switch in the axle. And if you for example have a wire broken the light wouldn't glow.

[Mark T]

They use a modular valve usually somewhere back in the right side of the frame. Likely something is going wrong in that area. Believe it or not, even stuff like the engine fan can have it's air from the back of the truck in some of them.  

[2014pinnacle]

Anybody know what’s behind the the 3 bolts that the air line goes through on the diff? 

[Joey Mack]

ok... the P.O.S. system is B.S.  it has a 25 MPH limiter... blah blah blah...   Just run an air switch of your own to the front diff, and make it work like they used to not to long ago...  the celenoid/servo bank on the left frame rail has the switch in it...   f-it... run you own. shut the original dash switch off so the ECU doesnt see it.... now it's up to you to shut it off when not needed... you can put a brake light switch in the air line attached to a buzzer, so you can be reminded that it's locked in, especially if you put a driver in the seat...  iv'e done this several times... Jojo