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Komatsu D38E-1 Pops out of Reverse

John C.

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The machine pops out of reverse but all the pressures are good. It doesn't matter which range it is in. Machine has a joystick control for direction, range and steer right or left. When in reverse it seems to me that the control has no detent left and easily pops out of gear. I checked the parts book which only shows a detent for the range selection. Basically turning the handle changes the ranges. There is nothing shown on the spools for direction. Looking at the diagram, it looks like only the opposing springs at the bottom of the spool hold the lever in place. I can't figure that out to be true without taking the whole thing apart. There is no hydraulic diagram showing the control in the service manual.

I'm looking for anyone who has some experience with this control before I start shutting the machine down and finding out that parts are in another country and weeks away. What holds the lever in the reverse position?

Thanks for any information.
 

Dave Neubert

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I would think it has some type of detent have you checked the linkage to make sure it is going all the way in reverse
 

John C.

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I had the boot off and checked the feel between the poppets and there is a little free play. The parts pages and the book breakdown for the control don't show a detent but I'm thinking there has to be something in there that holds the poppet down. I just don't want to put the machine down to pull the control and explore the guts of the thing. i might have to anyway. Thanks for the response.
 

Vetech63

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Back in the day I know a lot of the fiat-allis stuff used oil pressure that held a joystick position just like a detent. Not sure on this machine.
 

John C.

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I have the service manual. It doesn't show or say anything.

I was thinking of that but I'll have to take the thing apart to find out. It's looking like that is going to be the case.
 

Jgm

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Hi John, I don't have experience on that model in particular, but i had a look at my book, as you noted no plan, but it looks like it just a spring which holds it, like you mentioned. Just out of curiosity, does it hac
 

Jgm

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Hi John, I don't have experience on that model in particular, but i had a look at my book, as you noted no plan, but it looks like it just a spring which holds it, like you mentioned. Just out of curiosity, does it hac
Does it have a check valve, not that is leaking back to tank, but it's possible it held with pressure
 

John C.

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Thanks for the response. What do you mean by hac?
 

John C.

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I was thinking that in order for it to be held by pressure it would need some kind of pilot oil. An internal passage or a hose from the actual direction valve.
 

John C.

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I haven't got it fixed but I have figured out a few things. Went to the work site yesterday and with the engine not running I tried to move the transmission lever into gear. It just flopped back and forth. The engine has to be running in order for the control to detent into forward or reverse. I checked the book again and found a section that describes the operation of the thing. Basically there is a passage through the middle of the spools that go down and across to the bottom of the opposite direction spool and pushed it up. The are pushed from the top by a rocker block and the pressure keeps both spools in contact with the rocker at all times. If one is down, the other is up. I tried to order seals and new springs. Springs I can't get. One of the wiper seals I won't have till the end of October. Two O rings I won't have till the middle of October.
Is anyone else seeing parts supply slow up?
 

Vetech63

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I haven't got it fixed but I have figured out a few things. Went to the work site yesterday and with the engine not running I tried to move the transmission lever into gear. It just flopped back and forth. The engine has to be running in order for the control to detent into forward or reverse. I checked the book again and found a section that describes the operation of the thing. Basically there is a passage through the middle of the spools that go down and across to the bottom of the opposite direction spool and pushed it up. The are pushed from the top by a rocker block and the pressure keeps both spools in contact with the rocker at all times. If one is down, the other is up. I tried to order seals and new springs. Springs I can't get. One of the wiper seals I won't have till the end of October. Two O rings I won't have till the middle of October.
Is anyone else seeing parts supply slow up?
Yeah! No one is stocking much inventory. Even the simplest things I am having to have brought in from elsewhere. Election related?....maybe.
 

John C.

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I'm thinking more about bugs than politics.
 

John C.

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The machine got dropped off at my shop last Friday and I immediately ripped the transmission and steering valve out of the machine and tore it down. I had picked up all the seals the day before. Removing it from the machine is not as simple of job as it looks. Getting the fittings loose for the hoses was a bugger. The number 8 hose female fittings were next to a cut out in the cylinder block and you can only get about a quarter to a half a flat turn on the fitting. I thought I was going to go have to buy a cheap 15/16" wrench and grind down one side to get it to clear but I was able to use an old half length wrench to just get enough turn to get them loose. The two hard lines on the front were a real bugger. IMG_1338.JPG
 

John C.

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I removed the bottom half of the valve from the top half and looked into the spring wells for the transmission forward and reverse and there was some crud in the bottom. The machine is an older one but only has about 3,300 hours on the clock. Anyway it isn't something that I hadn't seen before. These spring wells are connected at the bottom. When you pull the handle back to go into reverse, a passage in the spool sends oil to the bottom and across which pushed the other spool up. That is what holds the direction in place. When you push the handle forward, you move the front spool down and reverse spool gets pushed up which cuts off flow and puts the transmission in neutral. 01 Valve Apart.jpg 03 Debris.jpg
 

John C.

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To pull the spools out you have to unscrew the nuts from the upper and the spool comes out the bottom. There are seals in the top which are a bugger to push in. The spools are beveled so when you push them up from the bottom they ease into the seal lips. The center spool is a rotary which is used for selecting the speed range. I cleaned the whole thing up and put it back together. I think one key to making the thing work is that those top nuts have to be adjusted so there is no free play between the tops of the spools and the crown ring above. There was about a half an inch of free play between the forward and reverse spools when I took the valve out. It seems they can only be adjusted when the valve is removed from the machine. It is kind of a cruddy design. Putting the valve back in was way worse the getting it out. You can't get a wrench on the nuts on the hard lines at the front of the valve. I had to get them as tight as possible and then use a hammer and chisel to get that last bit of tight. Anyway once I got that in I started looking for the oil leaks in the compartment. There is a safety shutoff valve underneath that shuts off oil to the transmission and steering valve above. I checked with the dealer who said there were two o rings on the spool in that valve and that there was an updated valve. I changed that out and the machine works and doesn't leak in the limited test I could do in my driveway. I'll know better when they put the machine back out on the job. 06 Leaking Safety Valve.jpg
 

JPV

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Nice job and write up John, I ran one of the first one of those that Pacific North Machinery (now Modern) got when Komatsu took the dozer line over from Dresser. The only real change that I could see was that single stick control and I liked it just fine.
 

John C.

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Thanks for the comment. It's a nice machine to run but not much fun to work on. The other part of this job was to reseal the ends of the spools for the hydraulic valve. I'll make another thread to show what that was about latter. There is a lot of marginal engineering in these machines that require a step by step approach to fixing something. If you are trying to repair item D, then you have to get there by removing items A, B and C first.
 
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