TuffTorq K46 Repair Guide with Pictures

[P901]

A post script.

While the transmission work was going on with the machine up on the lift we fabricated
a set of stainless steel spindles to allow the installation of a pair of X485 front wheels, (Craiglist 75$)
Photos, stainless steel spindles, wheels installed.

Made a tire pressure gauge using a WIKA liquid filled gauge/pipe nipple/tire chuck to allow accurate pressure measurements
down into the single digits. (WIKA liquid filled gauges 0-30psi range on Ebay, ~20$)
The factory manual recommends 10psi but the machine rides much better and is much easier on the grass with 5psi.
Such low pressures can only be registered with an accurate gauge.
It was apparent while experimenting with the tire pressure, by visual indication that while on a hard flat surface the tire contact
area increased to the full width of the tread at the reduced pressure. With the ten pound setting the center of the tire was in contact
with the hard surface.
It may be realized that the recommended pressure which creates the reduced contact area places an increased point load on the turf.

andrew

 

[P901]

Yes, been thinking along those lines.
The problem at this point would be to raise the location of the vent plug.
After the first oil fill I had the oil level a tad high and I was getting a little bit of "sweat" from the vent
cap. No big deal, a couple of drops that were easily wiped up and then no more after that.
I`m thinking now that if I turn a brass collar of the same diameter of the vent plug opening in the transmission case with a slight interference fit
that I can press the brass collar into the vent plug location and then insert the vent plug into the top of the
collar and retain the venting function.
Research has revealed that the units with the reservoir tank, X360 for example, use the exact same part number for the cap on the reservoir tank
as the part number of the vent cap on the X300. The cap for the reservoir tank is the actual vent cap, therefore this is where the factory retains the venting function on the X360, they vent through the tank. Air would be purged into the tank during operation, bubble up through the oil and then when the unit cools
down fluid will be drawn into the transmission. After a few cycles all of the air would presumably be removed from the transmission.
An inch or two elevation on the collar should do the trick and I don`t think that there needs to be a lot of oil contained in the "tube reservoir".
Just so long as there is enough oil in the tube while running when the pump draws down the level under load.

andrew

 

[doxford jim]

It might then therefore follow in our thought process that there may be no reason for the K46 to have received a bad reputation but for the simple facts that without the ability to change out the oil along with the additional function of being able to purge all of the air from the system that the K46 is in fact not able to receive the basic service due any precision piece of machinery to facilitate a prolonged period of service and reliability.

Cheers, andrew

Which makes me wonder if this so called oversight, is by accident or design. I think this is a deliberate act and as such, ensures that TT makes more money from their transmission. The claim that the transmission does not need servicing (JD) is bogus and untrue.

Thanks

 

[idakiteman]

L110 JOHN DEERE INSTALLED NEW PUMP ,MOTOR,AND BLOCK WORKED ABOUT HALF HOUR THEN WOULDN'T PULL AGAIN ..BLED THE AIR PROCEDURE SEVERAL TIMES NO HELP .. TOOK IT APART AGAIN JUST TO DOUBLE CHECK BUT EVERYTHING WAS INSTALLED RIGHT ..THE BACK TIRES WILL ROLL A LITTLE WHEN I PUSH THE MOWER AND THE ROD IS NOT PULLED .. ANY IDEAS ????

If the rear wheels roll w/ freewheel lever pushed in, then either the hydraulic circuit is open/leaking somewhere (or insufficient oil) or gears are stripped or not engaging as they should. I'd start by looking at the gear train (since that's easiest to inspect), starting w/ the reduction gears #42 & 66 (kit 100) in tufftorq website diagrams and follow the gear train thru the differential to the axles, looking for broken teeth or other issues that prevent engagement of mating gear pairs. If that looks good, take another look at the hydraulic side assembly: is some part in backwards?, or check for proper assembly of the bypass pin in the centercase and everything that contacts that pin: the washer between motor & centercase, and the bypass shaft & lever & rod. Good Luck

 

[pooleo]

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.

 

[P901]

Good morning,

You raise very good points for discussion.
I recognized the type of pump when I opened the case. It is an adaptation, [miniaturization], of what we had in the Navy known as "Worthington" type pumps.
In the larger industrial applications the part of the pump that is angled is actually adjustable to allow for the control of the output of the pump.
In our transaxles this angled face is fixed and we control the output of the transaxle by the amount of oil flow which is controlled by the pedal position selected by the operator.
As you have noted the angled, "swash plate" face is of aluminum alloy.
A bit of side information, years ago when the first Porsche Carrera`s came into our shop with aluminum cylinders I was surprised to find that the aluminum cylinders did not have an iron liner !!
It was an aluminum piston against an aluminum cylinder at engine speeds up to 10,000rpm !! I wondered what Porsche was thinking, how was this engine supposed to last for very long. In fact these engines were very tough. As an air cooled motor they ran slightly loose tolerances and could take a beating on the race track.
It wasn`t until further study that we were informed that the factory had applied a plasma coating, "Nikasil" or "Alumasil" that had imparted a very hard and wear resistant coating to the aluminum that would allow this level of performance.
Has TT applied such a coating to this high stress area ? Would be nice if they did, probably not for a lawn tractor.
Wondering also, what about the K58 or K66 upgrades? Does the design of these units get away from the [chrome?] plated piston faces running against the aluminum angled plate?
And if so, is this one of the direct reasons that these other units last longer ? Or is it simply a larger unit that is more capable of handling a heavier load over time.
One might think that if the K58 or K66 has the chrome pistons running against the aluminum face what then is the real reason that these units last longer if it isn`t a matter of physical size ?
If we take physical size, (and therefore the associated capability granted by being larger and better able to handle the load), out of the equation and if the construction uses the same methods relative to the types of metal in contact with each other then do we come back to the question of the qualities of the lubricants.
The quality of the lubricant being in direct relation to its ability to resist wear over time within the confines of the breakdown of the oil over time.
Freshly changed oil then being much more able to protect the aluminum plate from the piston wear?
Also, if we ask ourselves, how long do we expect this unit to last before we conclude that we "got our moneys worth".
If I recall correctly the K46 has a recommended duty of 1hr of mowing time 25 times per season with a life rating of 250 hrs = 10 years.
Seems a bit short to me but maybe that is the reason the tractor is ~3,000$ as opposed to 5,000$ or more. We got what we paid for.
I would be satisfied if I got 20yrs out of a unit that I could replace for 500-750$ but thats my perspective.
As you say the unit will fail, when, then becomes the question and how can we prolong the point in time of that event.

Cheers, andrew

 

[aquacure]

Just an update. I was able to figure out that the idler pulley that the back of the belt rides on is adjustable and it fixed my problem perfectly.

Very nice thread, unfortunately I found it a little late. I was given a 2003 LT 180 with a bad transmission. I purchased the below link from ebay.

John Deere New Replacement Hydrostatic Transmission LT150 LT160 LT170 LT180 | eBay

I believe it is a 46C. I installed and have been able to mow my yard with it. But I have been getting some slippng, surging to full speed then slowing down, on hills I hear a squeeling from the front pulley and even saw a little puff of smoke once. I installed a new drive belt with the new transmission but it still seems like the belt is slipping on the front pulley. Is there an adjustment to this belt or should I try belt dressing? Or maybe something wrong with the pulley? Any ideas would be helpfull.

thanks

 

[ehb]

Hello everyone and thanks for all the information in here, made me pull my K46AM too. It came equipped with reservoir, drain plugs and steel gears.

I changed the oil when it had done about 50 hrs to 10w50. It was a really nasty soup back then and I really wondered how this could be in a "new" transmission. Now I'm guessing it should have at least 400hrs on its back (8 years of service, no counter until recently) with mowing steep terrain (mowed in a risky sideways angle) and snow plowing abuse with extra weight on the back (I'm a leightweight). I'm fairly sure that the oil change back then has made a significant difference in lifetime.

Symptoms so far were:
- Grinding noise when the differential had to work (bad sign, I knew it)
- A little loss of max. speed (also found out the lever hadn't been fully engaged anymore by the linkage)
- Rough speed changes. I remember it reacting softer, but maybe I'm remembering wrong.
- Noise that sounded like really dirty oil in a hydraulic system.... Ha ha.
- Axle movement in-out (each side independantly too.. really starting to worry), left and right (outer bushing shot) AND swivel motion (inner bushing shot, which definitely hints to gear damage too)

So this thread (and the OP's YouTube videos) were very helpful in the decision to rebuild the transmission.

Now it's on the workbench and I'm as well disappointed how bad everything fits together in there - by design. The dimensions of the distance pipes and shims simply were wrong from in the beginning, which resulted in this disasterous damage. However, I'm amazed it held up for so long anyways. The parts (especially the steel gears) seem to have been of good quality. Once fixed in a manner as andrew (P901) suggested in the last few pages, I'm very confident the K46 would last at least 500hrs before any serious damage happens (if the oil is appropriately changed).

I will take close-up pictures of the gear damage tomorrow.
When I make the parts (distance pieces and shims), I'll take measurements and post them too.

I'm contemplating placing axial load bearings somewhere in there, but I haven't come to a conclusion yet. My terrain often requires mowing in a sideways angle, so that would be a very neat addition.

Thanks again, especially andrew for his latest posts.

Bye,
Stefan

PS: I forgot.. I have yet to look at the center case, but I imagine it's badly worn. I was wondering how much an anodic coating would cost... Then again, I need to remind myself that I mostly want to mow grass with it...

 

[Kyle_in_Tex]

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.

Before you mentioned this, I was thinking if a person got the aluminum center case out and had it hard anodized black. Black anodize is very thin but extremely hard. Not sure if it wouldn't flake off at the port centerlines or not. The port edges would have to be really debured nicely with radii. Would probably cost about $75 at a plating shop if you got it oil free and spotless prior to taking it in.

P901, as you know, there is a huge difference between bare aluminum cylinder walls (AKA chevy vega), and nikasil lined cylinders. Nikasil and such requires diamond tooling or grinding wheels to put a nick in it.

I guess the proper solution would be to machine off some of the face of the centercase and make a locatable, harder metal wear face with matching ports. If you have a CNC mill and shop at your disposal...

My lawnmower is a 2005, bought new and I cut about 1 acre with it. It now has 183 hours on it. I've not been into the tranny yet.

 

[P901]

Black hard anodize, now that sounds like a darn good idea.

ehb, radial thrust bearings? This is an intriquing thought.
I have also noticed a bit of gear noise under a full load climbing a hill.
I believe some noise is to be expected from straight cut, or "spur" gears.
We may realize and take some notice of automotive history from the early
days of transmission design when the majority of the units utilized straight cut
gears.
I`m certain we are all familiar with that whining noise from a vintage truck transmission
in the old black and white movies as it accelerated through the gear changes, straight cut gearing.
This whining noise then was effectively removed by the angle cut of the gear teeth that we have in our auto
and truck transmissions today. Also keeping in mind the angle/spiral or "hypoid" cut that
we have in the differential gearing to promote silent running.
Understanding also though that the machinery necessary to make the angle cut gears or hypoid gears is
a bit more sophisticated, ie expensive, therefore straight cut gearing for a lawnmower is appropriate given the
common speeds and loads that we encounter.
So a bit of noise from the straight cut gearing is to be expected although I`m certain that
it does promote transmission longevity when the parts are fitted together properly.

Yes, the Chevy Vega, too bad they didn`t go the extra step and plasma coat the cylinders,
but that was a different time and place. Brings to mind one of the early models of Louis Chevrolet
that had IRON pistons and an air cooled copper cylinder head.
Surprising that this particular engine did not go too far. The reciprocating loads must have been
phenomenal !

I was surprised to see the one guy on this thread that had taken the 400 grit paper and a porcelain tile
as a surface plate to perform the restoration of the pump mating surfaces, nice field repair you`ve got to love
a unit that can be brought back to life that way.
If this unit can be repaired in such a fashion and we see some posts where the people report having
terrible looking oil with the unit still running along with a significant service time on the clock the K46 might begin the get the reputation for being a
fairly resilient unit given the fact that by design application it was intended to receive no care or maintenance.

Questions,

How many K46 are in service total ? 100,000 - 200,000 ??
If there are that many in service how many have failed ?
Out of the ones that have failed did they fail early, less than 50 or 100hrs and if so what was the service
to which they were exposed.
Of the total number in service how many have gone beyond the 250hrs life rating per manufacturer?
How far beyond?

It would be good if this information was available and accurate but unless I`m in a state of overly positive
thought it seems as if the K46 is not that bad of a unit and with a little care we should get our moneys worth.

Best regards to all, andrew