Hard Shifting Tranfer IN/OUT of high/low sometimes - M929/A1 w/Allison

jaws4518

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I searched the forum on "hard transfer case shifting" and found a lot of good discussion on the topic. Maybe what I am experiencing is normal operation, but thought I would ask the question again. I'm not sure that I am having any problems but here's how my truck acts when you shift from high to low in either direction. First, it seems to shift fine if you are rolling a little or moving within the speed range limits. I wouldn't say that it is always a super smooth process. Of course, you must shift into 'N' first, then press and hold the actuation button for a couple of seconds, then pull or push the shift-lever in a easy fluid motion feeling your way through neutral to high or low. It's not always perfect shifting but probably the nature of the beast. So... the hard-to-shift problem I am asking about is when the truck is barely moving, or not moving. Usually shifts ok if I'm barely moving, but a little more difficult. If the truck is not moving, then it's kind of a "roll of dice" to get it to shift somewhere from being stuck in between high and low. I never force it. When I get in the stuck position, I just feel for that sweet spot then it shifts right in. I usually have to cycle the transmission in and out of gear a time or two, to get things back into sync. I need to review the shifting procedures again in the TM, but haven't yet. I think my M818 acts pretty much the same way. It's on jack-stands right now so I haven't been able to compare the two.

So, is what I'm describing normal? Any maintenance suggestions?
 

simp5782

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Sometimes you have to give it a little motivation but putting it in gear and then pulling it up to release the bind.

You can however remove the unlock solenoid ground wire from the steel plate on the drivers side of the transmission. cut the wire. add in a longer one and ground it to the bellhousing on the transmission bellhousing. It will give you a better ground. Behind that plate isn't very good an the plate is painted so it is a known problem for connection..

You can also get rid of the air pressure lock cylinder on the top of the transfer case that keeps air pressure on that shift lever. When you depress the button it unlocks the torque converter and unlocks the air solenoid on top of the transfer case and allows it to move. They alot of times don't work. By doing the single line system you will not have the lock on the High, N, Low shift. It is mostly made so that you can't just kick it out while driving or in the cab. It is just a safety for that but can be a pain for us.
 

jaws4518

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Okay, so it's normal. After I asked this question the other day I went out to shift it while parked. It was smooth as ever to my surprise. I guess smooth operation depends on locking and how the gear mesh is lined up for a smooth shift. I found that shift slow and easy works best.
 

74M35A2

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Sometimes you have to give it a little motivation but putting it in gear and then pulling it up to release the bind.

You can however remove the unlock solenoid ground wire from the steel plate on the drivers side of the transmission. cut the wire. add in a longer one and ground it to the bellhousing on the transmission bellhousing. It will give you a better ground. Behind that plate isn't very good an the plate is painted so it is a known problem for connection..

You can also get rid of the air pressure lock cylinder on the top of the transfer case that keeps air pressure on that shift lever. When you depress the button it unlocks the torque converter and unlocks the air solenoid on top of the transfer case and allows it to move. They alot of times don't work. By doing the single line system you will not have the lock on the High, N, Low shift. It is mostly made so that you can't just kick it out while driving or in the cab. It is just a safety for that but can be a pain for us.
Info like this is really beneficial. In addition to the common rebuild mis-hap of incorrect air line swapping to the T-case itself, something like this comes from real experience of playing with this stuff.
 
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