Help Please - Saf T Liner won’t go into neutral

[Curious Slug]

Right. It’s been a long while since I’ve posted here, which is mainly out of laziness and a lack of time. Sorry, I had planned on being a more active member of this community but our situation significantly changed and I’ve had no time. I’ll explain that later.

Our bus is nearly finished (I’m going to update the build thread from the road) but we’ve hit a problem. I was hoping that some of the more mechanically minded amongst you can help...

The bus won’t go into neutral after it’s been put into drive/reverse. It can go between drive/reverse, though sometimes you have to mash the button a couple of times and really press the break hard.

Important stuff -
Thomas 1998 MVP Saf-T-Liner (40ft pusher)
Cummins 8.3l
Allison MD30-60

Other info -
The bus sat being renovated for a year without moving. Developed a problem with the compressor - wouldn’t go into gear because the tanks didn’t build up pressure. Towed to a garage, compressor switched out. Drives now, just not going into neutral without turning the engine off and restarting. I need to get it safety certified before we change the use, mechanic said that he can’t sign it off unless it can go into neutral (referenced standing at road works as an example of when this is could be a problem). He said he thought it was related to the interlock, though I’m not sure if that’s correct as I didn’t thought the interlock was related to ignition.

Any help/advice you can give would be amazing, we’re really up against it and this has been causing quite a bit of stress! Thanks.

 

[ewo1]

When I bought my bus, drove it home from Kentucky, a week later it would not start and then it would not go into gear after I got it started.

Problem turned out was in the electronic messaging from the Transmission (TCM) and the shifter keypad.

Basically it was a wire that was not completely broken but broken enough to create problems.

Here are two link to my threads on this.
One is how I fixed it and the other is for a MD3060 troubleshooting manual.

Hope this info helps you out!

MD3060 - dead/dark shift panel
http://www.skoolie.net/forums/f33/md3060-dead-dark-shift-panel-24837.html

WTEC 3 troubleshooting manual
http://www.skoolie.net/forums/f33/wtec-3-troubleshooting-manual-24965.html

 

[Curious Slug]

Awesome reply, thanks. Sounds like you went through some stuff!

The fact that the keypad isn’t very responsive makes me think the neutral issue might be something to do with that, but I have absolutely no idea about this stuff. I’ll perhaps start there.

Can anyone elaborate on the interlock thing - is this at all a symptom that could be related to the interlock?

 

[ewo1]

I am by far no expert on this subject but my curiosity won't let me let it go....

Surfing the net I found several posts from other RV forums and it appears to me that the WTEC system is not so tough to diagnose.

It's either a failure in the wiring, problem with the VIM and on occasion the keypad does go bad.

On my bus, a 99 Amtran, the VIM is located in the rear engine compartment, passenger side. Big black box with the remote key switch start.

Inside the box is the VIM circuitry, 6 relays and two fuses.
All the relays on mine seem to be the same.
If yours is like this, double check the relays to see if they are the same and swap positions on them, move them around.

One of those relays is your neutral relay.
By swapping them around, if you neutral problem resolves and now something else is failing then I would suspect a bad/failing relay.

Another thing you should do is visually and physically inspect all connectors of the trans / WTEC wiring.

Unplug and replug all the connectors. If you have any dirt of corrosion on the pins themselves by unseating and reseating it might clean up the problem connection.

Also do not be afraid to give a very slight tug on the back side of the connector, where the wires come to the plug.
If they become corroded internally where you can not see it, it will create a high resistive open, simply a bad connection.
Current will have problems going thru a high open and could create intermittent signal flow to the TCM and or key pad.

IT not hard to do this just dirty and uncomfortable being under the bus but this is what any shop you go to will need to do anyway so save yourself the diagnostic money for real problems.

In MHO, I would tend to think that most wiring problems will be at the back of the bus where the wiring gets most road water /salts onto the connectors.

I uploaded a diagram, female plug to dash pad, that I made showing the pinouts on the connector for the push pad itself. simple voltage and continuity checks to do. This is where I started and it got me on the path to finding a bad wire.

Also another link to an Allison WTEC troubleshooting manual. Very comprenhensive, 400 pages!

http://ww2.justanswer.com/uploads/H...ison_transmission_md3060_trouble-shooting.pdf

Once you take a look at the manual, while the system performs many complex functions, the push pad control system is not that difficult to troubleshoot, just takes some time and patience.

Here is another link, one that I used to start my dead dark panel repair. Very informative and very brief instructions on how to troubleshoot both the WTEC 2 & WTEC 3 systems.

https://www.transmissioninstruments.com/troubleshooting/


good look and keep us posted!