M923 A2 HI LO Stiff shifting Problems

[Ultra Mag]

Been plowing 40 inches of snow 112 Hrs eat sleep in M923 A2. The Hi Lo shifting is areal PITA Had to keep airing down to get into hi or lo.Please help my arm is ready to fall off.

 

[VPed]

I have found that some trucks do not have the shifter adjusted exact enough so the electrical switch makes contact when the truck is in neutral. Try wiggling the shifter handle within neutral while pushing the button on the t-case shifter. Do this with the engine off but the truck aired up. With the engine off, you should hear the solenoid click when the switch closes. When you hear the solenoid click, shift the t-case.

If the adjustment is the culprit, your particular truck made need the shifter pushed forward while shifting the t-case or it may need to be pulled every time you want to shift the t-case. Once you determine the direction your truck needs fudging, you can make an adjustment to the shifter cable length (at the transmission) so that neutral on the shifter switch better matches neutral on the tranny. That could wait for a warm sunny day though, once you find the trick. Till then, just push or pull on the shifter as appropriate while shifting the t-case. Of course, this all assumes that is your particular problem. My experience is that it is pretty common though. It takes just a minute of listening for the click to find out if it is. Good luck.

 

[acme66]

X2 on checking the switch. I have also had good luck with lubricating the pivot and linkage and a few drops of air-tool oil in the interlock solinoid inlet line. Three trucks, one had issues with linkage, one the solenoid and one the switch. I think it comes from sitting but once you get her moving they seem to stay moving. Good luck!

Ken

 

[74M35A2]

These are great points, thanks and I'll check mine also. I thought there was another thread that said if you have to air down as he is describing, it could also be incorrectly routed air lines from a depot rebuild, was common? Hats off to the east cost snow. Hope you are making good money on it. Send us some action pics from the cab!

 

[Wildchild467]

I heard quite a bit of them were routed incorrectly. There are threads out there showing the correct way to route them. It does not seem that hard of a thing to check and if they are routed wrong and you fix it, it seems like an easy win. That would be fantastic!

 

[M35A2-AZ]

When I got one of my trucks the solenoid wires were not hooked up.

 

[73m819]

Also the anti shifting lock is not needed unless you have a wrecker where the lock keeps the transfer from going in gear while using the back end, just remove the air supply, plug both the air line and the shift lock. this is the same as airing down.

 

[WV New Guy]

I initially had some issues and once I lubed the linkage and started working the linage every week she works just fine now.

 

[timntrucks]

ill do these things and see where my problem is. thanks guys for posting this

 

[Ultra Mag]

ill do these things and see where my problem is. thanks guys for posting this

Thanks everybody for the help. Fixed one today with some adjustment & lube<BATA BING BATA BOOM.

 

[Swamp Donkey]

Also the anti shifting lock is not needed unless you have a wrecker where the lock keeps the transfer from going in gear while using the back end, just remove the air supply, plug both the air line and the shift lock. this is the same as airing down.

This is a picture of what Ron is talking about. I have my spare removed so this is a topside view. Remove the line from the cylinder and solenoid. This leaves you two holes to plug that have 1/4" NPT threads. You'll find an appreciation for stubby wrenches even if you do it from the top.

Mine was always easy to shift but the cylinder had an internal leak that was pressuring the T-case. It now shifts even better though. You don't have to worry about the button anymore after doing this.

 

[74M35A2]

A little more on this please. This part is not required on M939's unless it is a 936 wrecker? Then why is it installed on all other 92x's? On my 925A2, this is doing nothing, or is my reading of this incorrect (maybe)?

 

[Swamp Donkey]

A little more on this please. This part is not required on M939's unless it is a 936 wrecker? Then why is it installed on all other 92x's? On my 925A2, this is doing nothing, or is my reading of this incorrect (maybe)?

The cylinder pushes a rod that locks the T-case lever in the position you set it. When you push the button on the end of the shifter it operates the solenoid which sends air to operate the cylinder and lock rod. The cylinder is "air applied / spring return". This is why when the button acts up you can ease shifting by knocking down system pressure with the brakes. This is also why the T-case will be constantly pressurized if the cylinder seal leaks air. By removing the air line you effectively have no position lock for the shifter. It takes a lot to knock the shifter out of gear without the lock. If it does happen then it just got knocked out of gear...unless it's a wrecker.

I'm guessing here since I don't have a wrecker but I think the transmission must be in gear with the T-case in neutral to engage the PTO. If the shifter were to fall into gear with the PTO engaged, you'd probably either have movement of the truck or driveline damage. Neither of those would be good and make the lock necessary on the wreckers.

 

[73m819]

The cylinder pushes a rod that locks the T-case lever in the position you set it. When you push the button on the end of the shifter it operates the solenoid which sends air to operate the cylinder and lock rod. The cylinder is "air applied / spring return". This is why when the button acts up you can ease shifting by knocking down system pressure with the brakes. This is also why the T-case will be constantly pressurized if the cylinder seal leaks air. By removing the air line you effectively have no position lock for the shifter. It takes a lot to knock the shifter out of gear without the lock. If it does happen then it just got knocked out of gear...unless it's a wrecker.

I'm guessing here since I don't have a wrecker but I think the transmission must be in gear with the T-case in neutral to engage the PTO. If the shifter were to fall into gear with the PTO engaged, you'd probably either have movement of the truck or driveline damage. Neither of those would be good and make the lock necessary on the wreckers.

Yes, this is true, all the 939 series have the same transfer case with the wreckers having a pto, it is easier just to put the lock on all the transfers, I guess they were worried that the transfer would get bumped out of low at a bad time ??, the wreckers have the lock to keep the transfer from dropping into hi when the back end is being used, this could kill somebody, cause truck damage.

 

[74M35A2]

Understood. I didn't know this, thank you. Is this solenoid the only thing actuated by the push button in the end of the T case shift lever? I think that button is also somehow tied to the torque converter? Mine is slightly goofy, if I push the chrome button in while at an idle in neutral, the truck will jump forward about one inch, and it is repeatable. This is while not moving the lever, but just only pushing the button.

 

[sd39u]

My M923A1 will not shift into the low transfer. I push in the button and pull up on the handle but it does not shift into low. I haven't tried to force it for fear than I wouldn't be able to get it back into high transfer.

Presume the instructions on this list are a good place to start?

Thanks

Eric

 

[Swamp Donkey]

Understood. I didn't know this, thank you. Is this solenoid the only thing actuated by the push button in the end of the T case shift lever? I think that button is also somehow tied to the torque converter? Mine is slightly goofy, if I push the chrome button in while at an idle in neutral, the truck will jump forward about one inch, and it is repeatable. This is while not moving the lever, but just only pushing the button.

It does operate the lock up solenoid too. This is to help with shifting on the fly. I don't do it so it's not an issue for me. I pulled these paragraphs from the -10 Operators Manual. I removed some non-pertinent information to shorten it up. Actual pages 003-7 & 003-8

C. TRANSMISSION 5TH-GEAR LOCKUP SOLENOID VALVE - Activated by transmission control switch and transfer case switch, the 5th-gear lockup solenoid valve directs main oil pressure of transmission to the transmission governor system. This puts transmission in 5th-gear, creating less drag on transfer case synchronizer which permits smoother shifting from one transfer case drive range to another. Refer to TRANSFER CASE CONTROL SYSTEM OPERATION, for further details.

TRANSFER CASE CONTROL SYSTEM OPERATION The transfer case control system converts four-wheel driving power into six-wheel driving power, provides smooth shifting of transfer case into high or low driving ranges while vehicle is in motion, prevents transfer case from being shifted with transmission in gear, and provides hydraulic power for auxiliary equipment through PTO.

2. In order to shift the transfer case from one driving range to another, an interlock system working in conjunction with the 5th-gear lockup solenoid is used (MT654 transmission only). This system prevents the transfer case from being shifted unless the transmission is in neutral.
3. With the automatic transmission, several actions must occur in order to shift transfer case from one driving range to another. Because of the interlock system, the transmission must be placed in neutral. The transfer case shift lever switch must also be depressed.
4. The transfer case control system, through use of a PTO driven by the transfer case, also provides hydraulic power to operate the crane and rear winch on M936/A1/A2 wreckers.
5. Major components of this system are: A. TRANSFER CASE SHIFT LEVER SWITCH - When depressed with transmission in NEUTRAL, signals interlock solenoid valve to exhaust air pressure from interlock air cylinder and actuates lockup solenoid. B. TRANSFER CASE SHIFT LEVER - Is pushed down to HIGH for light load operations, and up to LOW for heavy load operations. Six-wheel drive is achieved automatically when transfer case shift lever is placed in LOW.

 

[73m819]

Everything else will stay working as before after the air is cut from the transfer shift lock, only now you will be able to shift the transfer easier and on the move.

 

[CNC2013]

I know this is old but I have not found a full answer to performing this. What I mean by that is, what do you do with the 2 open lines after you disconnect from the cylinder and solenoid? I understand plugging up the holes with the 1/4”NPT plugs but none of the threads explain what to do with the open lines that supply the air. I assume plug those as well right?

 

[simp5782]

I know this is old but I have not found a full answer to performing this. What I mean by that is, what do you do with the 2 open lines after you disconnect from the cylinder and solenoid? I understand plugging up the holes with the 1/4”NPT plugs but none of the threads explain what to do with the open lines that supply the air. I assume plug those as well right?

https://youtu.be/N7--6jxGDBM

Connect the bottom and top supply ports in the frame rail block together. its the simple solution