Bus Not Going Into Gear

[El Fudge]

I took delivery of a 1998 Saf-T-Liner with a Cummins 8.3l and Allison MD3060 recently. Unfortunately, I wasn't there for delivery so never saw it moving but it arrived under its own steam. The bus starts fine, after the compressor does it's thing the bus revs nicely in neutral. BUT I don't know how to get the thing going! How do I get it into gear?! The touch panel seems unresponsive, I can't select Drive or Reverse. When I press the Mode button, a light comes on but that's about it. Sorry, this seems a stupid thing to post about.

The air pressure is low as the seat has been disconnected from the air supply and not capped. This comes up as a red light on the dash and I can hear it. But the brakes seems to operate (I can hear them come on). Help!!!

 

[bluebird90]

First fix the air leak so the air pressure can build up. Many buses have a safety feature that prevents the trans from going into gear with low air pressure.

 

[RHOMBUS]

How low is the air? Is the buzzer going off? Are the air gauges showing less than 60 psi?

You can get a little plastic air valve from Home Depot or similar to close that line. I have several places I've done that while I'm building my bus. I got mine at Runnings for like $7 each.

Here's an example:
https://www.homedepot.com/p/Watts-Quick-Connect-1-4-in-Plastic-Straight-Valve-PL-3011/100112645


I'm not sure all of the ways the md3060 communicates with everything, but low air pressure *might* prevent the system from letting you put it in a gear. If you can't get the air up to 90psi on the 2 gauges, then I'd go cap that line.

After that, if it still won't shift, there are ways to get the transmission to show codes on that shift module to make sure it's actually communicating. I'll have to look up how that's done.

Again, first thing is charging the air system. I'll dig through my electrical diagrams and see if the low air pressure circuit does anything more than make the buzzer and light go off.

 

[david.dgeorge07]

My Thomas saf t liner with a 3060 will shift even if air pressure isn’t up. That doesn’t mean your will though. May be different.

The mode button is unrelated, and is had no function in our busses. For pto on dump trucks and stuff.

Is it blinking when you try to shift? That is what mine does if something is not right, like idle speed is high. It shows N but then will blink R or 6 if I try to put it in gear when something is not right for it.

 

[cadillackid]

definitely make sure the high idle is off.. there is a wire input for as shift interlock on the allisons that it wont go into gear if say your wheel-chair lift is not fully stowed..

-Christopher

 

[El Fudge]

Thanks all. I'm going to try to cap the air hose and will make a bit more of a detailed report of what is going on. Just to be sure, I would just press the D button on the panel to get it into gear, right? Foot on brake, like in some automatic cars? Anything else super simple that I might have missed?

 

[david.dgeorge07]

Thanks all. I'm going to try to cap the air hose and will make a bit more of a detailed report of what is going on. Just to be sure, I would just press the D button on the panel to get it into gear, right? Foot on brake, like in some automatic cars? Anything else super simple that I might have missed?

That’s how mine works. High idle turned off (mine goes off automatically when the brake is applied), foot on brake and parking brake turned off is how I do it usually.

I have heard of the shift controller going bad. Hopefully not what is the problem here.

 

[El Fudge]

Hey all, sorry for the delay in coming back. Good news is that it moves! I capped the line with some tape (not perfect, but works for now) and let the air build up to about 70psi. Foot on the brake pedal, shifted into first and moved a foot. Now I've just got to shovel snow to get further than that. Thanks for all your help.

 

[Tango-SKO]

Glad you ID'd the problem and it was simple. Good luck with the white stuff.

 

[Native-SKO]

In a pinch, a golf tee will plug the plastic air line.