923a2 won't shift out of neutral

[Jim Timber]

I'd actually start with the low fluid check. There's a procedure for checking it cold so you can warm it up to then check it properly.

 

[TexAndy]

The cold check procedure requires shifting into D and R while it is running to "fill the hydraulic circuits."

But what I'm wondering is if that will even happening if it isn't actually shifting out of N.


Second question: Straight 10W motor oil ok? Will the detergents in motor oil cause an issue? Looks like 10W motor oil is ok, per the TM, but I don't know about commercial motor oil w/ detergent.

 

[Jim Timber]

You've never had this truck running under it's own power right?

 

[TexAndy]

You've never had this truck running under it's own power right?

Correct. I've had the engine running, but I've never seen the vehicle move.

 

[Jim Timber]

How long was it idling before you tried to shift it?

I'm wondering if it's just got air trapped in the circuits and you haven't worked it out yet to build fluid pressure.

 

[TexAndy]

Not very long. I don't think I'm getting high enough voltage out of the alternator to properly charge the batteries, so I've tried not to run it long enough to kill the batts.


Would it hurt the transmission to run the engine for 10 or 15 minutes with the selector in 1-5 and my foot on the brake?

 

[Jim Timber]

I'm not an auto tranny guy, but I don't think you'd have any problems if you had it in neutral or park.

It's a diesel - there's no spark plugs. You should be able to run it without an alternator once you get it started.

 

[Jim Timber]

You might want to call Allison tomorrow and ask them. I've never heard a bad word spoken about their stuff. I'd think their CS is probably pretty decent too.

 

[Suprman]

I would check the oil and coolant levels before running the engine. If oil and coolant are proper you can let it idle it will be fine. If the trans fluid is at the correct level and it won't go into gear and drive, I don't think any amount of idling will help. Did you try reverse and 1-5 one at a time? How does the trans fluid look and smell. Does it smell burnt?

 

[TexAndy]

Engine oil and coolant levels were fine.

I tried reverse, 1-5, and all the selections below 1-5 down to 1.

I didn't drain any of the transmission fluid from the pan, but what I saw on the dipstick looked fine. Didn't smell or taste burnt.

 

[Suprman]

You tasted it? If all fluids appear ok and it won't go into any gear then chances are you have a mechanical failure in the transmission. You can drop the pan, replace the filters and change the fluid and see how it goes. My personal opinion is new fluid won't fix it. Take it to an Allison dealer see what they say about it. Could be something simple inside or it could need a trans. Transmissions are like plumbing, unless you really know what you are doing it should be left to someone who does.

 

[TexAndy]

Allison tech in corpus said it sounded to him like a pin on the other side of the shift selector sheared off or fell off. Paraphrasing, don't recall his words exactly.


Which doesn't sound so bad, except I don't know how I'm going to get at this thing the way it is. I'm going to try adding a little oil to it and run it for awhile and see what happens but...

He said it would have to be really low for it to not build any pressure at all. So that probably isn't the issue.

I don't think I want to take it down there. I'm kind of in "If I can't fix it myself, I need to cut my losses and give up" territory.

 

[Jim Timber]

You can't get the pan off in the truck?

 

[TexAndy]

I probably can, it's just at a friend's place down the road. I don't want to drain the fluid and drop the pan over there and kill his good will.

I'm going to flat tow it with a deuce over here, first.

Hopefully, dropping the pan will allow me to see a little more.

 

[mkcoen]

Okay I'm looking at the -24P to see if I can identify where there might be a nut loose (other than the operator - sorry but thought a little levity might ease the tension).

Can you tell if the selector cable housing is moving when the shifter is moved to a different position? I wouldn't think it should be just checking. If the housing isn't moving can you tell if the end of the cable is moving? It should in order to move the selector.

There should be a shoulder pin held to the selector lever by a cotter pin. If everything in that line is there and moving correctly then it has to be on the inside of the housing. I wouldn't think it'd be too difficult to drop the pan at that stage just to check that the remote control lever is actually moving what it's supposed to on the inside of the housing. If you're going to just try to sell the truck with a bad transmission then it wouldn't be any worse as a "drained" bad transmission.

I believe Airbornebandsman has a 939 tranny (bad) for sale and it might be worth picking up just to take apart and see how the shift lever is supposed to work. You could always sell it as scrap when you're done deconstructing it.

Let me know if you want some help. I can come down Thursday (club meeting tomorrow and pest treatment on Friday).

 

[TexAndy]

I'm pretty sure the linkage is good. I can see the selector lever on the side of the transmission move when the shift selector is moved.

Thanks for the suggestions on the bad tranny. I'll give him an IM and see how much he wants for it.

Next step will be to get it over here and drop the pan, I think. You're welcome any time of course, but I don't know that we'll get much done yet. I'm still kind of trawling for opinions.

If dropping the pan doesn't let me access that shift control lever/valve, then it will probably come down to dropping the transmission itself. But I'm not quite at that point. I've never dropped any transmission, much less a big truck transmission. Don't know if I would need a special jack or if I could just build a cradle to support the transmission and use a couple of normal automotive jacks to lower/raise it.

 

[rtk]

Just as a FYI , if you have NEVER dropped a HD transmission , please be CAREFUL . The Alison is a good unit but it does have some heft to it . Things could get ugly FAST , at the very least is a good flat ground to work on and a proper HD transmission jack and a READ of the TM's . You will be twisting wrenches on some big nuts and bolts ,so take your time and take pictures of the before and after in case you forget where something goes . I know it will be expensive , but you might be better off dragging it to the Alison dealer , what is your time worth . good luck , bob k

 

[TexAndy]

Thanks for the concern. I will be careful.

Looking at the allison owner's manual, it does appear as if the control valve body sticks down into the oil pan cavity.

Will tow it back tomorrow if I get a free moment. Then I'll drain the oil, drop the pan, and see what it looks like and take a few pictures for ya'll.

I do appreciate all the help.

 

[TexAndy]

Ok... pg 5-309 of the TM is where I think the issue might be.

That's on volume 4 of 4 in the pdf series. Page 317 of that file.

That stuff looks like what the Allison tech was talking about.

 

[mkcoen]

Ok... pg 5-309 of the TM is where I think the issue might be.

That's on volume 4 of 4 in the pdf series. Page 317 of that file.

That stuff looks like what the Allison tech was talking about.

From the looks of that the nut wouldn't have had to come all of the way off just loosen enough for the shaft to slide out of the key and start spinning freely. If that's the case should be an easy fix. If the shaft is actually damaged then that bad tranny might be worth buying after all for spare parts.