TuffTorq K46 Repair Guide with Pictures

[ehb]

I have just taken apart the rest of my K46AM. The pump and motor feel quite alright (very little play of pistons in bores), but the center case has some wear. Less than I expected though, except for those nasty scratches around the holes. I think I won't even replace the pump and motor and see what I'll do with the center case (sand it or mill it or coat it or replace the surface with something harder.. I'm not sure yet).

The differential gears are NOT made of steel but chrome plated powder metal and have serious tooth decay.
The other gears have wear all around too, so I will replace the whole gear part and add shims in the proper thickness in the process.
Straight cut gears can transmit more torque than angle cut ones too and in this application, noise surely doesn't matter.

I'm very confident the early oil change I did (mine had drain plugs, so it was convenient) saved the hydraulic parts from silvery-mineral-oil-death. The gear part however is terribly assembled/designed and can't be expected to last more than the 250hrs life time rating. It's not the quality of parts that's bad, simply their arrangement.

This is a little saddening, as even the K46 could have been a great transmission with only tiny bit more investment in production. I can't imagine an engineer screwed this up. The unit has to have been deliberately worsened by people higher in the command chain. "Make it break and make it cheaper!".
So regarding your questions andrew, I think you're in the ballpark with your numbers. There might even be more K46 around.

Now I too would like to know if the K66 and up have similar flaws.

Best of luck to the other rebuilders,

Stefan

 

[idakiteman]

I believe the unit is designed to fail. No matter how many times you (could) change the oil, the basic design is flawed. You have hard steel drums with what essentially comes down to having teet, under spring tension (plungers and springs), grinding into a soft aluminum case. You could change the oil every 2hrs. The unit will still fail. The center case should have been designed out of brass.

I asked Derrick at TuffTorq if the a main difference between K46/T40 trannys (reliable for mowing only, on flat ground, in mild temps, and even then often marginal) and the higher end trannys built for ground engaging applications was if the centercases of high end trannys were made of steel or some harder metal. He said "NO"....the higher end trannys starting at K57/58 incorporate an added "charge pump". This "charge pump" is a third "revolver" like device (similar to pump & motor) that mates to T40/K46 centercase, on the round face on the opposite side of centercase from the pump. In T40/K46, that centercase face is UNmachined (since nothing rides on it), but in K57 it is machined smooth to mate w/ charge pump. This charge pump in K57/58 achieves more sustained oil flow & a more reliable oil film to keep pump & motor revolver faces separated from metal-metal contact with their mating centercase faces. Above the K57/58, they start adding oil change capability and filters to boost lifetime, and maybe other things. So, centercases in the more durable trannys remain aluminum but it's better protected by oil film. K58 use begins in the X304 thru X360. But those are 1" axle machines. You can get the exact same K58 design durability in 3/4" axles with the K57. That's why TT sells the T40/K46 to K57 "upgrade service", and doesn't upgrade to K58. They upgrade your tranny to K58 durability but keep the axles compatible w/ your 3/4" wheels (that's a K57). Note that JD does NOT sell any tractors having K57, so there is no standard model of K57 available from TT that would drop into your JD tractor. K57's are all designed for other manufacturers & brands, so unlikey they'd fit the unique JD specs (transaxle mounting hardware, control levers, axle lengths to fit frame & fender widths, length of tire mounting sleeve bushings that go on axles just inboard of tires, etc.) . But TT will upgrade your T40/K46 internals to K57/58 durability, while keeping all its other components so it'll fit your JD tractor. Alternatively, you could find a K57 tranny and swap axles & external mounting hardware from your T40/K46 into it...but that probably costs more than having TT do the upgrade. Anyway, far as I've learned, centercase material in X360 is still soft aluminum just like T40/K46, and they use other means to boost durability.

 

[P901]

Good day Stefan,

Thank you for the photos and the description of the service that your machine has encountered.
You say your estimate of service time is ~400hrs, this then would be beyond what John Deere has given us
as a life rating of this component, 250hrs or ~10yrs if I recall correctly.

You mention the K66, I see where there is a vendor that offers this option as an upgrade, a bit expensive but
I`m certain it would lend to increased confidence in the tractor.
Curious that if we were to install a K66 then haven`t we simply installed a transmission that is larger than what would
have been required for a specific duty cycle. Of course this then would also increase the cost of the tractor outside of
what must have been determined through demographic studies for a certain segment of intended users.
To that end then, a loss of sales within that segment.

Also to parallel your thought, if the K46, K57, K66, etc. share the same method of construction and possibly share many of the same
materials, (the larger units do not use the sintered, [powder] metal gears?) then at some point in time these other units might as
well share the same failures simply at a later date due to the fact that they are able to be serviced and also that they may be
physically sized to bear more load.
No extraordinary information here with this !
One might wish to do a study of "Time between failures" versus increased cost of the larger units, has any true economy been realized ?

Would it not be of a great benefit to find that with a few shims and an oil change every now and then that the K66 upgrade would not be
necessary for the cost in the ~1,800$ range!

Yes, I would agree, any mechanical engineer would have recommended design specifications that would probably have produced a different
product. It is the same where I work, the quality of service delivered against the cost of delivering that quality.
These factors can be determined by people that do not have the direct relationship with the customer unto whom the quality of that
service is delivered.
It is not difficult to see then that there can be quite a disconnect between the two points of approach.

You say your unit came with the drain plugs and the reservoir tank.
Would you consider posting photos of these features?

Thank you, andrew

 

[ehb]

You say your estimate of service time is ~400hrs, this then would be beyond what John Deere has given us
as a life rating of this component, 250hrs or ~10yrs if I recall correctly.

Yes, and I think the hydraulic parts may still be ok (except for the center case). It wouldn't have lasted as long with the primary oil filling though.

You are possibly right in that a properly built K46 is sufficient for most of the jobs that can be done with the tractors it comes with. Especially when considering the information idakiteman cited two posts earlier. Thanks btw!
If the only addition is a charge pump, then I'm sure using the right oil and changing it often enough, we'll be fine.

You say your unit came with the drain plugs and the reservoir tank.
Would you consider posting photos of these features?

I'll post some up later, but you can also go to the parts catalog shop at https://www.tufftorqservices.com
When you choose Hydrostatic/K46 within "Catalog Shop", you'll see that almost all vendors except John Deere (and "Hop") have the extra tank. If you click on the illustration image of the K46AM, you'll also see the drain bolts.

I have yet to find a good solution for catching the side load. Since the axles are kept from slipping out by the c shaped retainers, a hardened distance piece that fits inside the final gear between the axles would be a good start. Neither axle could move in, because both can't move out. Then it's a matter of grinding the right washer thickness to adjust the differential gear clearance.
I would rather have a bearing somewhere, though.

Considering the oil: I know 10w50 is suggested, but since this is an engine oil, it's designed to keep particles in suspension (so they can be transported to the filter). A hydraulic oil such as HLP 100 (which has viscosities closest to 10w50) might be an even better choice, and afaik these rather let particles sink to the bottom, where they don't disturb anything. I'll use up my 10w50 before I try something stupid though. Please no oil discussion now though, they always end badly.

I'll drill and tap the original drain plugs to a larger thread, so I can fit at least M10 screws with a neodynium magnet in the middle.
It would then be a another idea to further split the gear and hydraulic compartment (with a flat piece of aluminium welded/glued in, directly under the fill plug, where that one magnet is located) so that less oil is interchanged between the two. The plugs independantly empty each compartment.

Further work will have to wait until replacement parts arrive...

I always have fun optimizing machinery, but honestly, it's more fun if it's just right to begin with...

Greets,
Stefan

 

[P901]

Good afternoon,

Thank you for the link to Tuff Torq.
I have been there before but did not focus on the "AM" variant.
It would appear as if the AM is a bit different than the model I have.
The AM has a reservoir tank that looks as if it is mounted on some type of an offset fitting.
The offset fitting appears to attach to the standard fill port which is located under the outer circumference dimension of the fan.
The offset fitting apparently allows the oil to flow from the tank neck under the fan and then into the gearcase housing.
Since the vent cap is located on the tank then there is no need for a second port in the gearcase
for a vent as in my model.
Now that I see that the Tuff Torq design engineers have produced a K46 type with the reservoir tank this is in a sense a confirmation
that the designer knows full well the value of periodic maintenance through the changing of the oil.
A bit disappointing that John Deere would not have included this option on the X300 even if the marketing department determined
that this segment of the group of end users was not inclined to perform this maintenance.
At the very least the type of user that would not even change the engine oil for example without taking it to the JD shop if the K46 transaxle had this feature it would allow the dealership to perform the service.

It would be encouraging to put together a set of shims and possibly a selection of bearings that would comprise an aftermarket
kit for the upgrade to the K46.
Encouraging in the sense then that the owners of these units would have yet another option outside of replacing the standard parts
with the expectation of the same degree of longevity or selecting the K66 choice at almost 2,000$.

Is the next level transaxle in the "300" series the K58 on the X320 really that much more capable?
If so what is the reason ? T he ability to change the oil, physical size, charge pump ?

Cheers, andrew

 

[pooleo]

I asked Derrick at TuffTorq if the a main difference between K46/T40 trannys (reliable for mowing only, on flat ground, in mild temps, and even then often marginal) and the higher end trannys built for ground engaging applications was if the centercases of high end trannys were made of steel or some harder metal. He said "NO"....the higher end trannys starting at K57/58 incorporate an added "charge pump". This "charge pump" is a third "revolver" like device (similar to pump & motor) that mates to T40/K46 centercase, on the round face on the opposite side of centercase from the pump. In T40/K46, that centercase face is UNmachined (since nothing rides on it), but in K57 it is machined smooth to mate w/ charge pump. This charge pump in K57/58 achieves more sustained oil flow & a more reliable oil film to keep pump & motor revolver faces separated from metal-metal contact with their mating centercase faces. Above the K57/58, they start adding oil change capability and filters to boost lifetime, and maybe other things. So, centercases in the more durable trannys remain aluminum but it's better protected by oil film. K58 use begins in the X304 thru X360. But those are 1" axle machines. You can get the exact same K58 design durability in 3/4" axles with the K57. That's why TT sells the T40/K46 to K57 "upgrade service", and doesn't upgrade to K58. They upgrade your tranny to K58 durability but keep the axles compatible w/ your 3/4" wheels (that's a K57). Note that JD does NOT sell any tractors having K57, so there is no standard model of K57 available from TT that would drop into your JD tractor. K57's are all designed for other manufacturers & brands, so unlikey they'd fit the unique JD specs (transaxle mounting hardware, control levers, axle lengths to fit frame & fender widths, length of tire mounting sleeve bushings that go on axles just inboard of tires, etc.) . But TT will upgrade your T40/K46 internals to K57/58 durability, while keeping all its other components so it'll fit your JD tractor. Alternatively, you could find a K57 tranny and swap axles & external mounting hardware from your T40/K46 into it...but that probably costs more than having TT do the upgrade. Anyway, far as I've learned, centercase material in X360 is still soft aluminum just like T40/K46, and they use other means to boost durability.

Thats very interesting. So does the charge pump go where the filter currently is...?

Also, about the metal shavings. Aluminum I think would be the majority of the metal in the oil. Since aluminum in non-magnetic. So I believe this is also a desing fail. The revolvers of the pump and motor shave away at the case......leaving millions of particles in the oil. :shocked:

 

[P901]

I asked Derrick at TuffTorq if the a main difference between K46/T40 trannys (reliable for mowing only, on flat ground, in mild temps, and even then often marginal) and the higher end trannys built for ground engaging applications was if the centercases of high end trannys were made of steel or some harder metal. He said "NO"....the higher end trannys starting at K57/58 incorporate an added "charge pump". This "charge pump" is a third "revolver" like device (similar to pump & motor) that mates to T40/K46 centercase, on the round face on the opposite side of centercase from the pump. In T40/K46, that centercase face is UNmachined (since nothing rides on it), but in K57 it is machined smooth to mate w/ charge pump. This charge pump in K57/58 achieves more sustained oil flow & a more reliable oil film to keep pump & motor revolver faces separated from metal-metal contact with their mating centercase faces. Above the K57/58, they start adding oil change capability and filters to boost lifetime, and maybe other things. So, centercases in the more durable trannys remain aluminum but it's better protected by oil film. K58 use begins in the X304 thru X360. But those are 1" axle machines. You can get the exact same K58 design durability in 3/4" axles with the K57. That's why TT sells the T40/K46 to K57 "upgrade service", and doesn't upgrade to K58. They upgrade your tranny to K58 durability but keep the axles compatible w/ your 3/4" wheels (that's a K57). Note that JD does NOT sell any tractors having K57, so there is no standard model of K57 available from TT that would drop into your JD tractor. K57's are all designed for other manufacturers & brands, so unlikey they'd fit the unique JD specs (transaxle mounting hardware, control levers, axle lengths to fit frame & fender widths, length of tire mounting sleeve bushings that go on axles just inboard of tires, etc.) . But TT will upgrade your T40/K46 internals to K57/58 durability, while keeping all its other components so it'll fit your JD tractor. Alternatively, you could find a K57 tranny and swap axles & external mounting hardware from your T40/K46 into it...but that probably costs more than having TT do the upgrade. Anyway, far as I've learned, centercase material in X360 is still soft aluminum just like T40/K46, and they use other means to boost durability.

Thank you very much for the clarification !
andrew

 

[Voyager6]

Is the next level transaxle in the "300" series the K58 on the X320 really that much more capable?
If so what is the reason ? T he ability to change the oil, physical size, charge pump ?

Cheers, andrew

I have spent a lot of time looking at Tuff Torq's parts site and have observed the following:

The motor and pump are now the same between K46 and K58. In the past, the K46 may have had slightly lesser design motor and pump). The K58 has heat treated steel gears standard. The input shaft and bearings are heavier duty to be able to stand more load back to the engine. Fan and pulley are different sizes (actually there are two fans for K58, one where the fan is on top of the pulley, and the other when it is below the pulley).

As mentioned, it has the charge pump standard. It always came with four magnets and the new design filter. It has heavier duty differential gears and a larger (more teeth) reduction gear to get more torque out to the wheels. This can be seen in the exploded view on tufftorgservice's web site. It has a slightly larger case than the K46, so it holds more fluid. The K58H has hydraullic output and has an external resevoir and externally changable filter (tank and support have be be bought from Deere). The K58H has drain bolts, but the K58A, B, M and N do not, but drain starter locations are pre-drilled inside the lower case cover. Axles are 1" versus 3/4". Not a big deal, but bushings are larger to accomodate this and thus have more wear surface and it can take a bigger load. Unfortunately, the play in the axles/differential appear to be about the same. Shims could be used to keep things together better.

The motion (forward/reverse) lever is further out from the center line of the transmission and the front mounting holes are in a different location due to the larger case. This I learned from personal experience in upgrading my X304 from a K46 to K58. The linkage is adjustable and the K58 front mount is available from Deere for about $3.

The K57 upgrade for the K46 retains the K46 less-durable final drive, reduction, and differential gears and 3/4 inch axles. Most everything else is upgraded to K58 level parts.


Voyager6

 

[P901]

Thank you for the detailed report of your research.

I think your description of the installation of the K58 provides a bit of insight for those of us
that may consider making this change.

It would still appear that filter changes or cleanings along with regular oil changes cannot be time mis-spent.
Do the pistons in the K58 still contact the aluminum swash plate directly as in the K46 ?
I`m wondering if the actual mechanical wear in the K46 is known to be located primarily in a certain spot possibly there
might be an effective upgrade for that portion of the unit.
It would seem that periodic oil changes would reduce the wear on the pump faces but if it also occurs that the wear
is seen on the face of the aluminum swash plate it would seem to be an easy fix to insert a hardened steel plate
over the aluminum thereby removing that weakness once and for all.

Thanks again, andrew

 

[rburke65]

On post #83 the OP says.....I found it also helps in the initial test after the rebuild to gently roll both tires in the same direction to get the unit moving again. I am getting ready to reinstall the rebuilt transaxle and I notice that I cannot rotate both axle shafts in the same direction! Each goes in the opposite direction!! Did I do something wrong? Am I in trouble? Thanks again guys....