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D160 Automatic Transmission

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I have an issue with my mid 1970's D160 garden tractor.   Plowing snow over the weekend it begain to make an awful grinding sound come from what appears to be behind the motor.  Once this happened,  all the hydraulic stop working and the forward reverse lever seem to be stuck in the middle position.   I shut down the tractor and was able to release the value on the pump and tow the tractor back into the garage.   When towing it back to the garage,   I noticed the rear wheel where moving ok (with the release valve open)  In the garage,  the forward / reverse lever will move back and forth.   I did attempt to restart the tractor again without any luck.  The sound seemed to be the same. 

 

I am speculating that I have a pump issue on the hydrostatic drive.   It' not the spline coupler with I know can spin out.   I did have this happen about 10years ago and at that time,  I removed the pump and had shop replace the shaft.   This time,  the shaft is definetly spinning the pump making a sound that I can only describe as a high pitch grind combine with what sounds like gravel rolling around inside of the a barrell. 

 

Does anybody out there have any advise?    Is there any checks that I can do to make sure it is the pump?  I friend has suggest lifting up the rear end and seeing if the wheels spin in opposite directions by hand (with our without valve closed?)   Is it possible that I may have damage something in the rear end?    I did notice after replacing the spline on the pump 10 years ago,  the tractor would still roll backwards with the value closed and the tractor not running.   I was not concerned at the time the tractor seem to move fine forward and reverse.

 

I do use the tractor for many task.  I have the rotor tiller,  snowblower,  deck,  category 0 connection with back blade.   It's a nice little tractor and I would like to keep it running.   It has the Onan 16hp engine which I have only had to rebuild the carb back about 10years ago due to some lugging issues.   For the most part,  engine is good burns a little oil (I change it every month in the summertime), and runs best on 90 REC gas.

 

If anybody has any recommendation for how to troubleshoot the most recent problem,  veryify it's the pump,  rule out any other possilbe rear-end damage, and possible recommend next steps,  I would be greatly appreciative.    Thanks  Marc   (FYI,  I live in Western Michigan between Grand Rapids and Kalamazoo).

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Down load the Sundstrand manual from here, it has a good set of diagnostics.  I suppose your friend was concerned about sheared differential bolts but since it rolls OK that is less likely.  You said the noise was behind the motor did you mean the hydro motor on the transaxle?  Or up by the engine e.g. your hydropump area??  Any signs of metal in the fluid???

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Might want to start by removing the 4 bolts that hold the engine to the frame and any pto parts in the way - slide the engine forward a little and separate the pump from the flywheel coupling. I'd suspect from your description the swash plate exploded - exactly what I've heard 2 of the older Sundstrand pumps do and that's pretty terminal for interior damage to them. Some just crack, lose pressure and sound like heck, but can be repaired pretty easily - others it's not the case. You could remove both spark plugs and rotate the engine by it's crank shaft and listen or feel for any binding in the pump too - might want to try that first.

 

The differential bolts as Paul mentioned and your friend was an issue prior to '76 models - they were too small as well as the differential side plates were too thin . They could shear the bolt(s) off and lodge the pieces between the bull gear and the transaxle housing, breaking or cracking it pretty good - most will start leaking oil right away- look at the area where the front of the drawbar hitch contacts the housing closely for oil or cracks. It's common to see an early D with a brazed differential housing - one early fix as well was folks boring out the holes for 3/8" hardened bolts - but the side plates could still fracture. Later models had heavier/thicker plates as well as the larger bolts - a later model rear end will bot up but it's not a fun job to change it out , nor repair an old one with the newer parts. Actually, almost nothing on a D is fun to work on but they are a beast and for their age/size they can do a lot of work and take the abuse of plowing pretty well - just can't beat on it hard nor ram into banks, ever...coupling at the pump usually goes first, as you know.

 

Not a whole lot of info on the D's compared to other models - but we're here to help.

 

Sarge

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From what you are saying, I personally would pull pump &  Hyd motor at a minimum, & tear both down for inspection & include inspection of final drive unit & strainer screen. I had a screen come apart (both ends came off the screen) & let contamination into hyd. pump, but I caught it before pump or motor were destroyed beyond refacing. I would say at a minimum you are looking at replacing the pump. As Sarge said check bolts in bull gear also.

 

 I have started putting a stainless steel wire through the strainers so if the epoxy fails, the screen & end cap will not have a chance to go through the gears. I had a spare hydrostat for an exchange and got to looking at it, & the strainer had come apart on it too, so I tore it down & it was in worse condition than the one I took from the tractor. Can not up load pictures at this point, so I have to use the thousand words. Ron

 

 

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Thank you all for the advise.   However,  after closer inspection this evening,  it's definitely the splines on the outside of the pump shaft that stripped out.   I believe this is good news as there hopefully nothing inside the pump that gave out.   This is the second time the shaft strip out on me (once about 9 - 10 years ago).   Does anybody have advise on what else that I should check,  or do for securing the spline shaft once I get the pump repaired.   I will have to locate another coupler for attaching to the new spline shaft.  Any recommendation on where I could purchase one of these?    Thanks    Marc

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I have  used coupling in good shape. Someone should have a service bulletin for the recommended Loctite to put on it, I'm missing that one. I can email picture if you want. Ron

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I had the same issue - blown splines on the shaft and a destroyed coupling. The shaft size is very small considering the torque load it handles as well as any shock loads to the system. I ended up having the old coupling machined out on the inside and pressed in a steel center (instead of hard cast) from a later model C1*1 . Had to chuck the C's pump pulley in the lathe and cut the weld out - the center will pop right out . Had that cut for a key way and the pump's shaft machined to match it - problem with doing that is those parts have to be timed due to the splines and that part required the machine shop to make a jig to get it correct. I also bored for a set screw right on top of the key - this keeps it locked tightly to prevent any potential wear. So far, so good - but it was almost $400 in machine work alone and I did some of it myself here. It fits tightly with zero slop - since getting that engine perfectly aligned to the pump is nearly impossible they just wear the two parts out until a load causes it to blow those splines, not a great design and the replacement shaft isn't cheap either.

 

I beat my head against the wall plenty with this mod to improve how the coupling locks to the pump splines - their design that allowed it to float is what would destroy them, this doesn't allow that and so far I've put about 20hrs on this setup -

 

Like I said , between the machine work, a used pump , welding farmed out (something I rarely EVER do) and miscellaneous parts - the bill for this repair was close to $600. It lives again, so far.

 

Sarge

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13 hours ago, R. L. Addison said:

I have  used coupling in good shape. Someone should have a service bulletin for the recommended Loctite to put on it, I'm missing that one. I can email picture if you want. Ron

 

 

TSB #305 is the Service Bulletin

 

Loctite 680 is the recommended retaining compound

 

 

Edited by pfrederi

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Sarge has a great solution, but it is beyond my skill level (and i think the level of area machine shops).  In addition to using the locktite i I put a Bolt and washer in the end of the input shaft.  i wanted to preclude any in and out movement of the drive coupling on the input shaft caused by any flex/movement of the pump relative to the engine and any misalignment.  .  This transfers some of the stresses to the rubber connector...they are easier to find if it winds up wearing it out.  Did it almost three years ago so far so good

 

One thing I do not understand is why the shaft only engages about 3/4 of the drive coupling depth  :think:

IMG_3518.JPG

IMG_3519.JPG

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Exactly what I questioned when I saw the parts' design - wtf were they thinking ? Instead of making a new and longer shaft to be used in the D's pump design (coupling versus pulley) they ran basically the same pump (sans the second long swash plate shaft in early models) as the C-series - bad idea. The lack of engagement to that cast iron coupling is just over half way - it's impossible for that thing to withstand even a 16hp Onan or Briggs engine, let alone a single cylinder or God forbid twin cylinder iron block Kohler. Just far too much low end torque and vibration for it to last any length of time. To add to this, the engine mounting holes were sloppily sized large so there's a lot of potential misalignment - with age on the rubber puck section it puts that much more strain on the pump's shaft joint to the coupling, which is why they blow out the splines. The machine shops original desire was to make a new shaft for the pump and that probably would have been a better idea - at least to get it away from the cast coupling and go with a more modern clamshell type that won't slip as easily and can handle the torque.

 

The cost and technical work was possible from River Front Machine in Spring Valley - this is an industrial machine shop/manufacturer that has some very odd and specific machining capabilities, lasers and some machines I have no idea what they can do, but their staff is very good at it and they could handle my request pretty reasonably. I will say this - that steel center turned out to be softer than expected, we should have tested it prior to having to use the EDM machine to cut the keyway - that would have dropped the cost to half on what they had to do. Indexing the keyway to the splines on the pump/insert was the biggest amount of setup time as he had to build a jig - that insert is just plain steel and could easily be broach cut on a press with the right dies, then just machine the keyway position on the pump shaft to match - much simpler and cheaper. The other problem is trying to not only get a proper press fit of the insert to the cast portion, but welding it . That is some very dirty cast iron with a lot of voids in it - that's why it was so difficult to cut the blown splines out and get it to run on center to the shaft's center line. Trying to weld that dirty cast and get it to flow into the steel portion without wrecking the splines in the process was almost impossible - I'll be surprised if some day it doesn't fail there.

 

Honestly, the best solution would be for someone to start making new pump shafts that are longer and use a heavier nose section for the engine coupling. It would solve the entire problem in one shot and just use a more robust coupling design with a replaceable shock dampener. There is no available new style coupling that will fit the existing shaft's splines - it's just too small and a weak design for the given power and shock loads from the hydraulic system. A good CNC design shop could easily do them out of the proper material - but that first one is going to be very expensive, some of this stuff is like t-shirts, lol. It's cost from the engineering portion of making certain a commonly available coupling design can be used that will do the given job and last without destroying the shaft in the process - or the engine. Until then, it's replace the shaft, try to find a good condition coupling or if you hit the lottery, a NOS one and start over with existing parts. It is what it is and why so many D's get parted out, shame but it's the reality of it. This fix was my way of tackling the problem and it has been done before by others, maybe not just as technical but the same in the end.

Just be aware - that Sundstrand built shaft is made from some seriously hardened steel , and it's not just on the surface - they destroyed a lot of inserts cutting that key way.

 

Sarge

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The whole problem with this set-up is alignment. I have spent a lot of hours with a dial indicator aligning motor/pump shaves on hydraulic units in deep, dark, crowded, very hot, and needless to say very oily holes when I was playing machine repair-man in my factory idiocy days. We worked to get them as close as possible, and the good ones would run for years much to most of the time.

 

I think the best design is the pilots machined on the single cylinder engines with the machined adapters & Lovejoy type (rubber spider) couplings would last forever.

 

The problem is these tractors depend (by design) on the couplings to support part of the weight (especially if the pumps are low) and this allows the splines to start moving against each other, and as oxidation sets in, it acts as lapping compound and over a period of time failure is inevitable.

 

These pumps have no means for proper location so I don't know if a redesign would be worth the effort or not as these are no longer in production, but maybe it's worth a little wondering.   Ron

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I agree - a modern Lovejoy type would be the way to go - but the flywheel surface is there for a decent hub to an already machined surface, or an adapter could be used for the hub type. I've watched the setup guys at the power plants try to align 2,500hp pump motors correctly after a rebuild job , it's a nightmare that can last for days with shimming and testing - no fun I'd bet for those folks. Last outage they went 2 rounds with one pump and a motor overhaul job - first time it turned into a 2,500hp vibrator so they had to start over according to the plant engineer, no one was happy that week. During testing we could hear the thing during lunch clear over at our break trailer - it was that bad, never did find out what was wrong with it as they wouldn't say.

 

I dunno, wish instead it could have been a belt drive setup and not too sure that couldn't be done - but the whole issue then becomes the linkage system on top of trying to mount the pump itself, probably not worth the effort. The tractor overall is a beast and for it's time was pretty stout , especially that frame but with care and time they can be kept in service. Those couplings are becoming a real problem now as decent used ones are drying up quickly - that will be the death of this model unless someone solves that issue.

 

Sarge

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