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John Deere 455 L&G Tuff Torq K92 Hydro Rebuild

59K views 29 replies 8 participants last post by  Dunkelstar 
#1 ·
I removed the Tuff Torq K92 transaxle assembly from my 1995 JD 455 L&G tractor tonight. Will open it up and do a rebuild parts needs assessment starting Saturday afternoon. I have the service manual. Any advice appreciated.
Original post below which describes the operating issues that caused me to pull the K92 out of the tractor tonight.
Thanks,
Ken
***********************
This is a question about my 1995 John Deere 455 diesel L&G tractor. I am the second owner and have owned it since 1997. The fluids and filters have been changed well within recommended service intervals. The engine runs great on this 1400 hour machine.
The problem started a week or so ago. Only when riding forward, there was a noticable whine noise in the hydrostatic transmission or transaxle. The whine noise which was speed dependent became progressively louder. Finally, the tractor stopped moving in the forward direction. When depressing the forward pedal there is a ratcheting noise but the tractor does not move forward. It does move normally in reverse. The mid-PTO drives the 54" mower deck like it always did. It mows great in reverse but the neighbors ask a lot of questions when I do that.
I have the Technical Manual and Parts Catalog. After doing some reading, and noticing the pin was not up on the FRONT directional control valve under the fuel tank, I replaced it with a new valve (Part # AM121248 because I do have the #40 Loader attachment). When I replaced the directional control valve I also changed the transmission filter, drained and replaced the fluid with new JD Low Vis Hygard. There was no noticeable metal in the drained fluid. It looked like it always does when I change it.
The work done so far has not corrected the problem of no forward motion. The ratcheting sound remains when one depresses the forward pedal. Reverse motion is normal and quiet.
Any suggestions appreciated.
Thanks,
Ken

P.S. I am a newbie on this forum. I have an engineering background, a rather complete set of tools and willingness to do the job. Work on my own cars, truck and motorcycle.
__________________
Ken
1995 John Deere 455 (Diesel)
 
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#3 ·
Sorry no suggestions for you, I will be curious on how difficult it is to tear your hydro down and reassemble. I have the same rear end on a 425 with a leak between the center case (the one with the relief valves on top) and the main housing. At this point the leak isn’t bad enough to warrant repair, but some day…. Pictures would be great.

Good luck.
 
#4 ·
The K92 is now apart. After 1400 hours of operation in my 455 tractor, it looks remarkably good inside with one exception. On the left side, behind the brake friction and steel plates, there is a bearing (CH14828) that holds the left end of the input gear shaft (AM878405). The gear is part # AM878401 and comes in a matched set with the input bevel gear. The bearing CH14828 has completely failed. Will update this thread with some cost details and photos when I start the reassembly.
Ken
 
#8 ·
Here is an opportunity. The Tuff Torq K92 out of my JD 455 tractor is completely apart. 100% of it is disassembled. All bearings and seals have been removed from the main case. I had some machining work done to clean up the bearing recess for the bearing that failed (see original post above). If someone want pictures of anything inside a K92 please ask. By the way, it is pretty amazing how many parts fit into that trans case!
I should also mention that a very thorough service manual on the K92 is available for download from Tuff Torq's web site. It is a great supplement to the John Deere Technical Manual.
Ken
 
#9 ·
Well my leak on my 425 is getting worse, I am thinking that I’ll have to fix it soon. I would be interested in pictures of parts between the transaxle center case and the main housing. How difficult was it to work on the hydro unit? I would consider myself a novice at mechanical work, I’ve done oil changes, brakes, and carb work but that’s about it. I’m hesitant about doing the work myself but certainly can’t afford to have a dealer do it.

I have the TT K92 service manual, to get to the seals between the center case and main housing it appears that I would need to remove the hydro from the rear end, remove the charge pump, remove the center case. Sound about right?

Any feedback would be appreciated.

Thanks
 
#10 ·
The JD455 is running again and did its usual nice job mowing the lawn yesterday. This followed the repair process of mating the original hydro pump, motor and center case to a more or less complete gear box that I bought used on E-Bay. Now I can rebuild the original gear case without time pressure and will probably keep it as a spare unit. The original problem was a bearing failure manifest as no forward motion of the tractor accompanied by a ratcheting noise when pressing the go pedal. The bearing that failed was JD Part CH14828 (Koyo 6005 or equivalent) and supported the left end of the Input Gear Shaft.

One thing I want to highlight for now is that it is a good thing to have more than one reference when doing such a job. For example, the Tuff Torq K92 service manual on Page 38 does not show the two O-rings that seal the shaft of the swash plate where it exits the Right Cover of the Transaxle Case. The O-rings (a.k.a. "packing") are shown in the JD Parts Catalog as Part # CH17653 on page 50-4. Trust me, the O-rings are required. It is possible to install the O-rings after the transaxle is installed in the tractor but it is a hassle. The O-rings took care of the leak!

I will post some pictures of the parts as requested in particular by
JWILL1776. Photo posting will occur prior to Friday.

More to follow.......
Ken
 
#11 ·
JWILL1776

There are three PDF format photo files attached of the hydro assembly including the center case, charge pump and motor. Note the six O-rings on the back of the charge pump housing. The old ones were really out of round (cross section) and were all replaced upon reassembly.
Hope this helps you. Please ask any questions that may come up.
Thanks,
Ken
 

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#12 ·
itsagass,

Thanks for the pictures they should help. I did purchase the JD service manual and downloaded the TT K92 manual.

I really need to pull off my seat pan to understand where my leak is coming from, my best guess is the seal between the center case and main housing. In your opinion would I have to remove the entire transaxle to take off the charge pump, motor, and center case? I know the service manual says to but that seems like a lot of stuff to disconnect.

It appears that these three groups come off in sections and not all in little peices, is this your experience? I hoping to get in there and replace the seals with minimal disassembly.

Any special tools required that you can think of?

How long did it take you to get the transaxle off the machine? I’m thinking a second set of hands might be useful for this.

Its probably going to be a few weeks before I can attempt the repair, the grass is growing to fast…..
 
#13 ·
I have more pictures. If there is anything you need in the way of photos or part numbers please let me know.

The "seal" that you mention between the center case and main case is a gasket. Before going through all of this, one might also want to check if the vent valve on top is venting fluid due to an overfill but I assume you already checked that.

As far as what can be removed without removing the transaxle assembly from the tractor frame, the hydro pump does come out and that is how the JD Tech Manual recommends to remove it. It MIGHT be possible to remove the entire hydro front end (pump, motor and center case) from the transaxle with it in the tractor frame but there are some things that may fall out in that process that are really best to keep clean and organized.

It is not difficult to get the transaxle out of the frame. These things (doing this from memory) have to come out or get disconnected and the first few have to happen anyway to get the pump itself out:

Drain trans fluid and filter. I recommend putting the empty filter back on after draining to keep residual fluid in the housing as you move it around.

Remove seat pan (rear fender assembly) one 6mm bolt on each side
of seat and four 6mm nuts and bolts holding floor pan to rear fender assembly. Bolt threads are 6mm. Hex heads are 10mm.

Remove tail light bulb holders from sockets and disconnect connector to seat switch prior to lifting seat pan off frame.

Lift and move fuel tank off to the side or disconnect the two hoses to fuel pump and fuel pump wiring connector and remove the tank completely.

Remove drive shaft from engine to hydro pump- two bolts @ pump end on splined shaft. Three bolts from underneath at rear of engine at coupler. You may need a strap wrench or other means to keep the coupler/shaft from turning as you loosen the three bolts.

If you are going to remove the transaxle completely from the frame you will need to disconnect on the left side the brake linkage and differential lock linkage. These are both simple cotter pin fasteners.

On the right side disconnect the linkage from the GO pedal to the swash plate linkage a.k.a. forward/reverse control arm. Access the bolt through the hole provided for this in the frame rail. You will have to hold the nut on the back side of the linkage.

The hydraulic lines and cylinder to raise/lower the mower deck can remain as they are.

Disconnect the connector for the PTO solenoid.

Take out the two bolts on each side of the frame that go into the axle housings of the transaxle. Preferably with a helper for five minutes, chock the front wheels and jack up the frame in front of the transaxle high enough so all transaxle components will clear the frame (it helps to first remove the two bolts that hold the transaxle dipstick). Removing the dipstick and its housing reduces the height one must raise the tractor frame to get everything clear of the frame. Pull the transaxle out to the rear. Lower the tractor frame on jackstands.

If you take the rear wheels off after separating the tractor from the transaxle it is now easy to get the trans unit on a bench. Estimated weight is ~ 100 pounds or so.

It took me about two hours to get the transaxle out and about 1/2 hour to put it back in. BY FAR, most of the time was spent in rounding up the parts.

There are two O-rings behind a snap ring and washer that seal the swash plate shaft. These sometimes leak. There are also seals where the mid-mount PTO shaft exits the case at the bottom front and a differential lock shaft seal on the left side near the back. There is also a seal cap on front of the hydro motor. The hydro pump is sealed at its rear face to the center case with six O-rings. The center case seals to the main housing with a large gasket. The hydro motor is sealed to the center case with a gasket.
The rear cover, right side case cover and both axle housings are sealed with silicone type form-in-place gasket material where they mate to the main case. There are also axle shaft seals out toward the ends of the axles.

Other than basic rachets, metric sockets, extensions, wrenches and pliers (for cotter pin and hose clamp removal), you may also need snap ring (retaining ring) pliers depending on how far you go into the disassembly process. As with any transmission related project, it is important to have a clean work table.

I am an engineer and a very experienced DIYer but a relative newbie on this forum. That said.....happy to answer any questions or provide photos, part numbers, etc. This forum has been a huge help to me.
Ken
 
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#14 ·
Ken,

Thanks for the detailed response, I printed a copy and will use it as a supplement to the other tech docs I have.

I got all my seals and gaskets on order through a local dealer, should have them in a week or so.

Since I’m a novice at this type of work I’m trying to enlist some help from a guy at work. He used to work for Sundstrand Aerospace the sister company of Sundstrand that made hydro units for JD many years ago. This gentleman use to be a quality engineer for the hydro units used in an aircraft to convert power from the jet engine to the generator. Off the top of his head he described the entire theoretical application of the hydro. It might cost me a few beers and a pizza but I should have some decent help.

The only other question I have was what type of sealant did you use on the diff lock washer? The local JD tech said there wasn’t a true seal there.

If something else comes up I’ll let you know.

Thank,

Jeff
 
#15 ·
Jeff,
Ah, the old beer and pizza bargain......good thing the IRS hasn't figured out a way to tax us (yet) on those deals.

You asked about sealant on the differential lock washer. My guess is you have the differential locking shaft seal in mind. This seal is John Deere part number M806040. If you really did mean differential lock washer please send more information on that.

The silicone sealant I used was from the JD dealer. The product name is Hylomar 101 Gasket Maker and Silicone Sealant. A 3 ounce tube was $10. I'm sure there are many products on the market that you could use as a suitable sealant.
 
#16 ·
Four photos are attached of the disassembled K92 transaxle from my JD455 L&G tractor noted in the original post above. I now have two complete transaxles. One has been operating well since re-installing in the tractor a month or so ago. The other one is completely apart. If anyone wants photos of anything else in the K92 please let me know. I will assemble the spare unit next weekend (July 17th or 18th).
Ken
 

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#18 ·
I just wanted to give my update on my situation. As stated before I was loosing about 12 oz of fluid per hour due to a leak. Thanks to advice from Ken and others I took the entire hydro out and replaced seals at the charge pump, center case, and motor. A friend of mine helped me complete the job, the whole thing took about four hours. $100 in parts compared to the $1200 a dealer wanted to charge me. I’m going to call my attempt a success event thought I still have very small leak ( One or two drips overnight after using the GT).

My advice, download the K92 service manual from the Tuff Torq site, maybe pony up the bucks for the JD service manual (I did, seemed to help). Get a second set up hands to help. No pry bars or use of excessive pressure and keep the whole operation clean. Oh, put down a huge piece of cardboard on your floor, there’s a heck of a lot of oil in there that doesn’t all come out through the drain plug.

Ken – Did your smaller replacement O rings from JD fit properly for the charge pump? (Five of them I think) I got the kit from the dealer and they were too big, there was no way I could get them to sit in the groove long enough to reassembly the pump, they would just poop out like they were oversized. $36 for that kit and only one fit properly, I ended up using my olds O rings for the time being, no leaks.

Thanks MTF!

Jeff
 
#21 ·
I’m not really sure on the cost difference between the two, I bought everything from a JD Dealer. Looking at the TT site I think you could get things cheaper, I just don’t have a good parts breakdown from TT with their part numbers. You could always call TT, I did once to ask some technical questions, very helpful. One shocker is the hydro oil from JD at $20 a gallon, you’ll need two.

Let me know if you need anymore reference material from JD, I might be able to help out and email it to you. :)

Jeff
 
#22 ·
Ok, just read the instructions on how to use the TT catalog site with parts diagrams, parts are definitely cheaper, that $36 dollar seal kit from JD that I was complaining about, $12 from TT. Arrrghhh!
 
#23 ·
I bought the oil already from Hogan Walker and some other items. They are cheaper on most of their stuff than JD, but they do not carry all the parts that JD does. Wasn't too bad, $15 a gallon and shipping was reasonable as long as you have a few items to buy. I changed the fluid and filter just to see if it would help. It didn't. I won't complain about the price too much. I changed the fluid in the tranny of my wife's volvo and they wanted $16 a quart for that stuff and I needed 10 to 12 quarts. Ouch!
 
#24 ·
Jeff,
Glad the leak is about gone.
The O-rings stayed in without moving around when I replaced them on the bench. The entire transaxle was out of the tractor.
Ken
 
#25 ·
Gungyspliff,
I was thinking about the problem you described of low speed with your tractor. Has it been getting worse over time or was it a sudden change and is now stable just slow. ? Is any metal apparent in the fluid? Do you have the service manual? If you have a loader, does that operate at the normal rate of movement?

If everything else seems normal and there are no unusual noises, one possibility is that your hydrostatic pump is either going bad, a valve plate is scored and bypassing fluid or a relief valve is bypassing high pressure fluid.
Ken
 
#26 ·
I am not sure what happened to it. I bought this used and it had been setting a while when I got it. I was told it had a problem with the transmission. I didn't pay much for it so I am not really worried about it. I changed the fluid and filter. The old fluid looked fine. I didn't see anything bad. No loader, but that would be awesome to have! The previous owner had all the manuals and parts book.
 
#27 ·
Brought this back from the dead . . . some good info in here. I'm going to have to replace the differential shaft seal and am not sure if the entire transaxle needs to be removed to do this.

Is is does need removed, what other seals should be replaced at that time? I was thinking the swash plate o-rings for sure. Thoughts?
 
#28 ·
Dunkelstar,
I have attached a photo that was included earlier in this thread on July 10, 2010 that shows what I think you mean by "Differential Seal". It is the seal around the differential locking shaft in the upper left (approx @ the 10 o-clock position) of the photo and is John Deere Part number M806040.

The honest answer to your question is I am not sure if you can get that seal out with the transaxle in the tractor frame. The seal is not a very tight fit in the case recess and, if you can get a tool on it, it is likely that you can get it out. Getting the new seal in should be straightforward once the old one is out. Of course, access will be easier if you remove the seat and rear fender assembly which you would have to do anyway if removing the transaxle assembly.
Hope this helps. Please report back your experience so that we all know the answer.
Ken
 

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#29 ·
Dunkelstar,
One more thought.....swash plate shaft O-rings and front PTO shaft seal (my tractor does not have a rear PTO) might be a good thing to replace if you can do without too much added effort. If you have no leaks where the hydro mates up to the gear case I would leave those alone unless you are "GOING IN" for more major work as I had to do on the bearing diagnosis and repair.
Ken
 
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