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Discussion Starter · #1 · (Edited)
I am looking at this John Deere LT 155 and the transmission will not turn the wheels on the ground when engine running. When you jack it up and get all pressure off the shaft turns a little...but when you grab it with your hand it will stop without much pressure. Does this sound like major problems inside? The splined shaft with the pulley on top the tranny is all good and is not stripped by the way..everything there spinning like it should. The plastic fan is like new so no worries there.

I was trying to find the name of this tranny on some nameplate stamped or riveted somewhere but I can not find one. I think it might had been some sort of decal or sticker towards the back of the mower..which I guess would be front of tranny or back?? But it fell off because I can see the adhesive mark where it was. Any other stampings anywhere else in the tranny housing I might find to tell the exact kind of tranny it is? I am thinking it is a Tuff Torq K51 B but I am not 100% sure. Reason I say this is some guy told me all 155s had this type of tranny?


Also I noticed one of the keys that side in slot in the wheel shaft was missing when I removed the tire. The tire looked to be recently replaced as it still smelled new. Would not having this key cause the tranny maybe to overheat and burn up because one side was maybe spinning and one side was not? The side which was missing the key was on right hand side...I will call it the passenger side like on a car.




















 

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the mad scientist
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I am looking at this John Deere LT 155 and the transmission will not turn the wheels on the ground when engine running. When you jack it up and get all pressure off the shaft turns a little...but when you grab it with your hand it will stop without much pressure. Does this sound like major problems inside? The splined shaft with the pulley on top the tranny is all good and is not stripped by the way..everything there spinning like it should. The plastic fan is like new so no worries there.

I was trying to find the name of this tranny on some nameplate stamped or riveted somewhere but I can not find one. I think it might had been some sort of decal or sticker towards the back of the mower..which I guess would be front of tranny or back?? But it fell off because I can see the adhesive mark where it was. Any other stampings anywhere else in the tranny housing I might find to tell the exact kind of tranny it is? I am thinking it is a Tuff Torq K51 B but I am not 100% sure. Reason I say this is some guy told me all 155s had this type of tranny?


Also I noticed one of the keys that side in slot in the wheel shaft was missing when I removed the tire. The tire looked to be recently replaced as it still smelled new. Would not having this key cause the tranny maybe to overheat and burn up because one side was maybe spinning and one side was not? The side which was missing the key was on right hand side...I will call it the passenger side like on a car.


The transmission is a TT k51b JD part # AM122742

Sounds to me that the pump is toast, unless the relief valve is stuck.
 

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Discussion Starter · #3 ·
I am looking at this John Deere LT 155 and the transmission will not turn the wheels on the ground when engine running. When you jack it up and get all pressure off the shaft turns a little...but when you grab it with your hand it will stop without much pressure. Does this sound like major problems inside? The splined shaft with the pulley on top the tranny is all good and is not stripped by the way..everything there spinning like it should. The plastic fan is like new so no worries there.

I was trying to find the name of this tranny on some nameplate stamped or riveted somewhere but I can not find one. I think it might had been some sort of decal or sticker towards the back of the mower..which I guess would be front of tranny or back?? But it fell off because I can see the adhesive mark where it was. Any other stampings anywhere else in the tranny housing I might find to tell the exact kind of tranny it is? I am thinking it is a Tuff Torq K51 B but I am not 100% sure. Reason I say this is some guy told me all 155s had this type of tranny?


Also I noticed one of the keys that side in slot in the wheel shaft was missing when I removed the tire. The tire looked to be recently replaced as it still smelled new. Would not having this key cause the tranny maybe to overheat and burn up because one side was maybe spinning and one side was not? The side which was missing the key was on right hand side...I will call it the passenger side like on a car.


The transmission is a TT k51b JD part # AM122742

Sounds to me that the pump is toast, unless the relief valve is stuck.
Any photos of how the pump looks and where it is located in this unit? Also the valve?
 

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Diesel Power
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Also I noticed one of the keys that side in slot in the wheel shaft was missing when I removed the tire.
OK lets take a step back here. First, it would be normal for only one wheel to spin with the back of the tractor jacked up and the engine is running with the forward pedal pushed down unless the machine has diff lock and it is engaged(yours does not). Second, if you happened to grab the axle shaft that was not supposed to be spinning at the time it would feel like the trans was slipping. Third, if you replace the keys on both axles and install the wheels and drop the rear onto the ground, what happens then? Also, with both keys installed and both wheels on with the machine up in the air it would be normal (when the engine is off) for the wheels to spin in opposite directions when you spin one by hand....does that occur? Finally, is the free wheel valve all the way in? We see this problem here all the time when someone changes a tire and forgets to put the key back into the shaft. Some guys actually have bought machines for dirt cheap because the PO thought the trans was shot, and it was just the missing key.
 

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Discussion Starter · #5 ·
OK lets take a step back here. First, it would be normal for only one wheel to spin with the back of the tractor jacked up and the engine is running with the forward pedal pushed down unless the machine has diff lock and it is engaged(yours does not). Second, if you happened to grab the axle shaft that was not supposed to be spinning at the time it would feel like the trans was slipping. Third, if you replace the keys on both axles and install the wheels and drop the rear onto the ground, what happens then? Also, with both keys installed and both wheels on with the machine up in the air it would be normal (when the engine is off) for the wheels to spin in opposite directions when you spin one by hand....does that occur? Finally, is the free wheel valve all the way in? We see this problem here all the time when someone changes a tire and forgets to put the key back into the shaft. Some guys actually have bought machines for dirt cheap because the PO thought the trans was shot, and it was just the missing key.

I tried putting new keys..starting her up and lowering back on ground..will not go move an inch. I jacked up again and started her up and wheels would barely move. I spin a little by hand then it moves tires little faster but I can stop the tires with my hand..so that is not good.
 

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Proud Wheel Horse Owner
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Step 1: Make sure that the lever that allows the tractor to be pushed around, is working, and moving the lever that it actuates on the transmission. The transmission won't power the wheels if it's stuck in free-wheel (push-me-around) mode.

Step 2: Make sure that the belt tensioning system for the transmission drive belt is working correctly, and that the belt is being tensioned properly. The transmission won't move the wheels if the belt is sliding on it's pulley, or the engine pulley.

Step 3: If you've confirmed the above 2 items to be good, and both axles DO have their keys in place (it will not move if the axles are just spinning inside the wheels because someone lost the keys), then the problem is inside the transmission

As you saw in my thread about repairing the trans in the LT155 that I had, the problem was simply clogged internal screens. I show a photo of the trans opened up, so you can see the screen.

If you have the skillset, tools, and a clean area to work, this is a DIY job. Simply remove the transmission, open it, clean the screens and polish the plates on both pump motors, reassemble, add 5w/50 synthetic to both areas of the trans, and you're back in business with a fully functional and completely silent transmission.
 

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Discussion Starter · #8 ·
Step 1: Make sure that the lever that allows the tractor to be pushed around, is working, and moving the lever that it actuates on the transmission. The transmission won't power the wheels if it's stuck in free-wheel (push-me-around) mode.

Step 2: Make sure that the belt tensioning system for the transmission drive belt is working correctly, and that the belt is being tensioned properly. The transmission won't move the wheels if the belt is sliding on it's pulley, or the engine pulley.

Step 3: If you've confirmed the above 2 items to be good, and both axles DO have their keys in place (it will not move if the axles are just spinning inside the wheels because someone lost the keys), then the problem is inside the transmission

As you saw in my thread about repairing the trans in the LT155 that I had, the problem was simply clogged internal screens. I show a photo of the trans opened up, so you can see the screen.

If you have the skillset, tools, and a clean area to work, this is a DIY job. Simply remove the transmission, open it, clean the screens and polish the plates on both pump motors, reassemble, add 5w/50 synthetic to both areas of the trans, and you're back in business with a fully functional and completely silent transmission.
Im not sure how to polish the pump plates or actually know how the pump looks up close to tell..I never opened these before. What does the screen look like very close?


By the way I tried the little pull push rod in back of the mower in and out many times....the one used if you want push the mower......Mower tranny still will not work. What did you use to polish the surfaces? How much oil to add once you put all back together as there is no measuring stick. Also if you measure what comes out..what if the thing was low on oil in the first place?
 

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Proud Wheel Horse Owner
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As I've mentioned, my photo shows the filter and one of the pumps. The filters simply get blasted out with carb cleaner, and then compressed air, until they are white and opaque again. The pumps come apart, and the plate(s) that the rotor(s) run against, get wet sanding on a flat surface with WD-40 or PB Blaster, on a piece of flat wet/dry 400 or 600 grit paper.

Re: fluid level. If yours had lost fluid, it would be an oily grimmy mess. So if you don't see that, it's not low on fluid.....it's simply stopped pumping because it can no longer suck any fluid through the filters. Or the pumps are worn out (not very likely).

Re: how much oil did I put back in. I filled it. Can't remember if it took more than a qt. It may have.
 

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Discussion Starter · #10 ·
Took tranny off today and opened oil cap. I am not sure what correct level should be. It is even with bottom hole. Is this what it is suppose to be? Also I flipped it to drain all oil out and it looks like only 3/4 of a quart came out and there is no more inside. Oil looks clean and not dark . I also see on the bottom of the casing a stamping K51. The decal or plate that was on the back of the tranny came off and so this is the only numbers I found to identify this one. Would this be just a K51 as I really thought it was a K51 B. I will break her into tomorrow and look inside. Wanna know about the oil level now though if anyone knows.


















 

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Former MTF Admin.
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IIRC from my rebuild of the K46, the fluid is supposed to be even with the bottom hole. What I can not recall is how much fluid came out when I did mine. but I was'nt concerned with that at the time. I imagine you will still have some trapped in the pump side of the tranny which will come out once you open the case. Don't know for sure on the K51 :dunno:. But when you go to replace the fluid according to Tuff Torq's chart it takes just a hair over 2 quarts of 5W50 synthetic https://www.tufftorqservices.com/EnvEEdefault/FlatHTML/TechInfo/docs/fluids.xml .

I don't believe the designation of K51B or K51A makes much difference when it comes to the internal workings http://www.tractordata.com/lawn-tractors/000/0/7/73-john-deere-lt155-transmission.html just knowing it has the K51 TT transmission is key. The good folks at Tuff Torq could elaborate further and if you need to do replacement of parts, which I suspect you will, they will provide the parts and answer any questions you may have :fing32:.

One tip I can give you is, take lots of pictures when you open the case at all angles, they will be invaluable when you go to replace parts and put this back together. Looks like you have a good digital camera there with the pics you provided, so you're set to go with that :).

Best wishes in this endeavor for successful outcome :trink39:.
 

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Discussion Starter · #12 ·
IIRC from my rebuild of the K46, the fluid is supposed to be even with the bottom hole. What I can not recall is how much fluid came out when I did mine. but I was'nt concerned with that at the time. I imagine you will still have some trapped in the pump side of the tranny which will come out once you open the case. Don't know for sure on the K51 :dunno:. But when you go to replace the fluid according to Tuff Torq's chart it takes just a hair over 2 quarts of 5W50 synthetic https://www.tufftorqservices.com/EnvEEdefault/FlatHTML/TechInfo/docs/fluids.xml .

I don't believe the designation of K51B or K51A makes much difference when it comes to the internal workings http://www.tractordata.com/lawn-tractors/000/0/7/73-john-deere-lt155-transmission.html just knowing it has the K51 TT transmission is key. The good folks at Tuff Torq could elaborate further and if you need to do replacement of parts, which I suspect you will, they will provide the parts and answer any questions you may have :fing32:.

One tip I can give you is, take lots of pictures when you open the case at all angles, they will be invaluable when you go to replace parts and put this back together. Looks like you have a good digital camera there with the pics you provided, so you're set to go with that :).

Best wishes in this endeavor for successful outcome :trink39:.


2 quarts seems like a lot when mine drained only 24 ounces at the most so far. I wonder if a lot is left in the case somewhere as I not had a chance to open the case up yet. Seems to me the pump could not hold but a pint at the most? If one was to accidentally overfill it what would happen? As for your links you posted They will not work for me. It says page can not be found. :dunno:
 

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Hmm, well the links work fine for me, sorry you can't see them :dunno:.

The first link is just a chart from Tuff Torq showing the recommend fluid replacement for their transmissions IE: the K51 takes 2.25 liters which is just a tad over 2 quarts.

Second link is from tractor data showing the transmission in a LT 155 is a K51.

Third is the link to Tuff Torq's website. But you can locate it easily enough.

As far as overfilling, I don't think you can as the fluid would just come out the fill hole, but to play it safe, I would only use the recommended amount.

Visiting TT's website you will find the schematics and useful information on your transmission. I printed out their entire diagram of mine and it did assist us tremendously when doing the part replacement and getting it back together right.
 

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I am going to see how it goes with your K51 rebuild. I have friend that has a Scotts LT with K51A that stops moving after it gets used for few minutes. Looking forward to seeing what you find with yours.
 

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Father Deerest
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Lift up that little filter with a magnet tip, how much oil is on that side of the hydro. I top off the fluid to the bottom of the cap. The pump and motor and valve body may be shot as stated by another member.
 

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Discussion Starter · #16 ·
I opened up the transmission case tonight and took some photos. Not really sure what I can tell is bad by just looking in here. If anyone sees anything so far by these following photos that looks out of the ordinary feel free to add your comment.























 

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Discussion Starter · #17 ·
Just found this on a site explaining what to look for once you open up a hydrostatic tranny.....but I am not sure what exact part of the block to look at..a block for that matter. What portion is the block?


(The running surfaces of the cylinder blocks MUST be flat
and free from scratches. If scratches or wear are found on
the running surface of the cylinder block or center section,
replace the parts.)
 

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For some reason I thought I read that you were back in business.?? Sorry that you aren't.
 

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Father Deerest
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First clean an area and set out paper towel for later.What you are looking at is the hydro motor with pistons, between this and the valve body is the small hydro release pin, the 3 screws is the valve body this is going to be a little tight but will pop up from the spring loaded hydro motor under the valvebody. An axle runs from the valve body through the motor, fixed swash plate and the brake rotor, as you pull this whole assembly straight up the spring loaded pistons in the motor you are looking at will want to push the swash plate out so hold on to it. Set on the paper towel and slowly separate the assembly and inspect where the motors contact the valve body for scoring or excessive wear.
 

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Discussion Starter · #20 ·
First clean an area and set out paper towel for later.What you are looking at is the hydro motor with pistons, between this and the valve body is the small hydro release pin, the 3 screws is the valve body this is going to be a little tight but will pop up from the spring loaded hydro motor under the valvebody. An axle runs from the valve body through the motor, fixed swash plate and the brake rotor, as you pull this whole assembly straight up the spring loaded pistons in the motor you are looking at will want to push the swash plate out so hold on to it. Set on the paper towel and slowly separate the assembly and inspect where the motors contact the valve body for scoring or excessive wear.
Anyone have any photos of what actual scoring on the valve body will look like? I notice a lot of semi-circle scratches on the tubular pistons in the motor and pump..you can see on the photos I posted. Is this normal ?
 
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