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12 Speed Poppining Out Of Gear


Warpman89
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hey guys, i got an 88 r688st with the trtxl1070b 12 speed, and lately it has been popping out of gear. it happens in 4H under a load while accelerating and in 5H while coasting. It does not happen in any other gear or in direct range in 4th or 5th, only 4th High and 5th High. Whats the deal here? Its got about 375000 untouched miles, so is it just getting old or what? thanks

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I'm going out on a limb with this but, Warpman i'm sure you may have thought of this also. I would think the linkage to the 4th and 5th gear is out of adjustment.

The other side of me wants to think it might be cause you are living too close to Rob and we all know weird stuff goes on over there. But I hope that's not the case.

mike

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I'm going out on a limb with this but, Warpman i'm sure you may have thought of this also. I would think the linkage to the 4th and 5th gear is out of adjustment.

The other side of me wants to think it might be cause you are living too close to Rob and we all know weird stuff goes on over there. But I hope that's not the case.

mike

Naw, I don't think it has much to do with the proximity to myself but I would put stock in wear of the shift forks, rails, and poppets. Of course this would be a great time to rebuild the air cylinders, and ensure the operating pressures from the output of the regulators is where it should be.

Rob

Dog.jpg.487f03da076af0150d2376dbd16843ed.jpgPlodding along with no job nor practical application for my existence, but still trying to fix what's broke.

 

 

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Naw, I don't think it has much to do with the proximity to myself but I would put stock in wear of the shift forks, rails, and poppets. Of course this would be a great time to rebuild the air cylinders, and ensure the operating pressures from the output of the regulators is where it should be.

Rob

Maaaan i'm glad I was hoping that was the case. :pat:

mike

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Naw, I don't think it has much to do with the proximity to myself but I would put stock in wear of the shift forks, rails, and poppets. Of course this would be a great time to rebuild the air cylinders, and ensure the operating pressures from the output of the regulators is where it should be.

Rob

well, where do you think i should start? would you agree that there is nothing wrong with the main box? the issue must be something to do with the splitter, right?

or is it the opposite, is the problem in the main box? it just occured to me that 4th and 5th are probably shifted by the same fork, however, like i mentioned before, the popping out only occurs in High range split...

Edited by Warpman89
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well, where do you think i should start? would you agree that there is nothing wrong with the main box? the issue must be something to do with the splitter, right?

or is it the opposite, is the problem in the main box? it just occured to me that 4th and 5th are probably shifted by the same fork, however, like i mentioned before, the popping out only occurs in High range split...

I'm not that versed in that transmission so others would be able to guide you better inside the guts but the top cover containing the air cylinders unbolts easily. It is not difficult to rebuild that part. I would say the 4th, and 5th speed are actuated by the same fork but it sounds to me like the actuator fork from the low, to the high side is not fully engaging due to faulty parts. This could be an air regulator that has went bad outputting too little air pressure to hold the sliding clutch gear in position, a worn shifting fork that pushes and pulls the slider clutch gear, or internal leakage withing the shift cylinders that control the low to high transition. With the top cover off of the transmission, a lot can be ascertained by looking at the working parts. You don't need to drain the oil to do this either. As you rebuild the shift cylinders, go through the "selectair" valve, (shifter handle) in the cab also.

Rob

Dog.jpg.487f03da076af0150d2376dbd16843ed.jpgPlodding along with no job nor practical application for my existence, but still trying to fix what's broke.

 

 

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Also make sure the trans to flywheel bolts are still tight and not loose enough to let trans gap open.

Hi Glenn, I'm sure you meant trans to flywheel housing bolts are still tight.........

Rob

Dog.jpg.487f03da076af0150d2376dbd16843ed.jpgPlodding along with no job nor practical application for my existence, but still trying to fix what's broke.

 

 

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I'm not that versed in that transmission so others would be able to guide you better inside the guts but the top cover containing the air cylinders unbolts easily. It is not difficult to rebuild that part. I would say the 4th, and 5th speed are actuated by the same fork but it sounds to me like the actuator fork from the low, to the high side is not fully engaging due to faulty parts. This could be an air regulator that has went bad outputting too little air pressure to hold the sliding clutch gear in position, a worn shifting fork that pushes and pulls the slider clutch gear, or internal leakage withing the shift cylinders that control the low to high transition. With the top cover off of the transmission, a lot can be ascertained by looking at the working parts. You don't need to drain the oil to do this either. As you rebuild the shift cylinders, go through the "selectair" valve, (shifter handle) in the cab also.

Rob

Service Hint!

You can pull the large pto cover on the side of the rear section and watch the spliter work from there by having someone operate the switch while you look in the pto opening!

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Service Hint!

You can pull the large pto cover on the side of the rear section and watch the spliter work from there by having someone operate the switch while you look in the pto opening!

I will have to give that a try. To make myself more clear, when i say "popping out of gear", i mean the shifter lever is literally moving out of gear into neutral in 4H and 5H. In 4H, when i split from direct to high and reapply the accelerator, if i don't physically hold the shifter in 4th it will start popping out, and even when i hold it in gear, it takes a little muscle to hold it in gear. 5th gear is similar, except it only happens when i am coasting, not under acceleration. 4th and 5th gear work fine in Direct, it is only when they are in High that this problem is occurring, so i am not sure if it a problem in the main box or the splitter box, or both...

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I will have to give that a try. To make myself more clear, when i say "popping out of gear", i mean the shifter lever is literally moving out of gear into neutral in 4H and 5H. In 4H, when i split from direct to high and reapply the accelerator, if i don't physically hold the shifter in 4th it will start popping out, and even when i hold it in gear, it takes a little muscle to hold it in gear. 5th gear is similar, except it only happens when i am coasting, not under acceleration. 4th and 5th gear work fine in Direct, it is only when they are in High that this problem is occurring, so i am not sure if it a problem in the main box or the splitter box, or both...

I just spent 25 minutes typing you a reply and the website threw me out during the upload, losing the information. Been a real consistent thing for the past couple of weeks. I'm now on a different computer.

Give me a call, 309-219-2070.

Rob

Dog.jpg.487f03da076af0150d2376dbd16843ed.jpgPlodding along with no job nor practical application for my existence, but still trying to fix what's broke.

 

 

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I just spent 25 minutes typing you a reply and the website threw me out during the upload, losing the information. Been a real consistent thing for the past couple of weeks. I'm now on a different computer.

Give me a call, 309-219-2070.

Rob

If the stick is moving about then its in the main box!Check for peices on the drain plug small ball bearings. the main shaft maybe floating!

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If the stick is moving about then its in the main box!Check for peices on the drain plug small ball bearings. the main shaft maybe floating!

Exactly.

Rob

Dog.jpg.487f03da076af0150d2376dbd16843ed.jpgPlodding along with no job nor practical application for my existence, but still trying to fix what's broke.

 

 

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Hi Glenn, I'm sure you meant trans to flywheel housing bolts are still tight.........

Rob

Thanks Rob for helping me out. I begin to need help more than i ever needed. I have been told that the trans mounting bolts being lose on the 12 speed can make them junp hi side on the splitter. Dont know because i have never had one before. I wished i did have one.

glenn akers

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Thanks Rob for helping me out. I begin to need help more than i ever needed. I have been told that the trans mounting bolts being lose on the 12 speed can make them junp hi side on the splitter. Dont know because i have never had one before. I wished i did have one.

Glenn I think both of our minds move faster than the fingers do. I don't need to think too hard on things I know well and try to convey the thoughts but have to proof read myself constantly to ensure what is thought, gets typed.

I have one of those 12 speeds but it supposedly has a problem and I've not torn into it yet.

Rob

Dog.jpg.487f03da076af0150d2376dbd16843ed.jpgPlodding along with no job nor practical application for my existence, but still trying to fix what's broke.

 

 

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thanks for the suggestions, i think i will check for the tightness of the tranny mounts and the bellhousing before i start opening stuff up, and if i still cant figure it out, i'll give Rob a call as a last resort... :P

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thanks for the suggestions, i think i will check for the tightness of the tranny mounts and the bellhousing before i start opening stuff up, and if i still cant figure it out, i'll give Rob a call as a last resort... :P

Yes , loose bellhousing bolts will cause this, and if the stick is pushing out as you say it is definitely in the main box. Also a loose fork will cause this , worn teeth on the sliding clutch and/or mainshaft gears, also a worn stub on the shifter and/or worn gate on the fork,also worn selective washers ,broken snap ring that hold mainshaft gears in place,broken detent spring . there is alot more pressure on the gears in high range .

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-UPDATE-

Started using it today but now when i shift to High on any gear, there is a loud "whining", and sometimes when i would put it back in Direct, the whining continued. if i shift to High while stopped and go through all the gears in High, skipping Direct, there is no whining, so im thinking that maybe the air shifter is not functioning properly. this loud whining only happens when i shift while moving so im thinking it just isnt shifting fast enough. all bellhousing bolts and tranny mounts are tight. driving in Direct only without splitting works but limits my top speed

so, how can i test the air shifter mechanism?

and, what would it cost to have the back half of my tranny rebuilt?

Edited by Warpman89
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