Lost Reverse on my D200?

[gzx3sc 0]

My D200 will take a spell every now and then where it looses reverse. It's only happened twice after pulling a yard roller for awhile. The fluid never got past 140 degrees F so it's not like I was working it too hard. It also won't hydraulically slow down when going from forward to reverse. I've read about the acceleration valves and all of that but I don't see what could go wrong with them? The manual talks about small passages ways that might be clogged? Anybody have an idea? :hide:

[wheeledhorseman 574]

I have a D-200 with a Sundstrand reversing problem as well it works fine going forward but in reverse it will just about creep for a few moments if I'm lucky. I've checked the motion control linkage system which appears to be moving the valve lever as it should. The oil is clean and at the correct level, I haven't changed the filter as if blocked the tractor wouldn't go forward. The implement lifts work fine - its just reverse that doesn't work.

As the pump and motor are separate I was thinking of slackening off the four unions at the motor end to compare how much oil comes out in forward and reverse mode next in an attempt to identify if the fault lies in the pump assembly or the motor.

Come on guys - someone out there must have encountered this reversing issue before.

[wheeledhorseman 574]

In view of the overwhelming lack of responses I'm going it alone with no previous hydro experience and just the Sundstrand manual for help. The fualt finding procedure when a tractor goes in one direction only lists just three possible causes to investigate starting with the linkage.

As previously mentioned the control linkage seemed to be working ok but decided to take the side panel off and check it out in detail. Discovered that by design it only allows a small amount of lever movement for reverse compared with forward presumably to limit the reversing speed. To make sure that this observation was correct I dismantled the linkage system leaving just the lever on the pump. Even being able to put the lever into full speed reverse made no difference to the lack of movement so the fault does not appear to be with the control linkage.

The next port of call according to the manual is to check out the charge check valves on the pump, the reverse check valve being situated between the push valve and the charge valve on the other end of the pump so it was off with the other side panel. The problem was that there doesn't appear to be one on my D200. The casting on the pump has never been tapped to take a plug and the internal end of the shaft is blanked where the valve would seat. At this point the purpose of the two hydraulic valves mounted at the rear under the fender became apparent. They are plumbed into the motor and I assume perform pretty much the same function but in a more robust way. The valves are mounted into an aluminium block and look identical so I carefully unscrewed them and swapped them over the theory being if one was defective the tractor would now go backwards but not forwards. It actually made no difference so I guess both of these valves are ok.

The final port of call is to check the reverse acceleration valve which relies on oil bleeding through a tiny hole in the metering plug to make it work and which, if blocked, would prevent the valve from working. Oil would simply flow from the high presure circuit to the low rather than passing through the motor. Removing the valve is quite straight forward but prepare to catch some oil which will empty out from part of the hydro motor. Dismantling the valve was not as straight forward as the manual makes out in suggesting it is held with a cloth. Holding it a firmly as I could it simply wasn't possible to budge the hex head of the metering plug to remove it.

It being the end of the day I decided to leave it till tomorrow. The valve body is machined aluminium so will be easilly damaged but I guess I'm going to have to grip it lightly in a vice between a couple of bits of soft wood. On the plus side the body has what are termed 'relief flats' on one side which should help to stop it turning as I undo the hex head of the metering plug. I'll keep you posted. I will get my tractor to go backwards again!

[multihobbyguy 35]

I wish I knew something about hydro's so that I could help you out. Seems like you are chasing down the culprit. Good luck tomorrow!

[gzx3sc 0]

The acceleration valves for forward and reverse seem to be held in place totally different than the check / relief valves for the accessory hydraulics which has me puzzled. They appear to have a big slot for a "huge" screw driver to get them out. I've yet to come up with a tool to get them out and they are deep in a counter bore! These need to be checked for dirt etc. I'm sure I'm reading the same manual as the other guy trying to figure this out. I had the same thought on the remote relief valve but I've not seen a schematic to know how its plumbed and if it truly is for forward and reverse? It probably is but I'm not 100 % convinced.

I changed the oil and filter against my better judgment knowing full good and well that wasn't the issue but what the hey. It didn't help by the way.

Now I'm in the process of replacing the pump. After using it doing some drag leveling it was fine until it sat for about 10 minutes then it would barely pull itself forward back up to the barn. After the oil change the pump was noisy and wouldn't hardly go then took off like a bullet. I'm guessing the pump was trying to self prime and when it did I had he lever full forward. If the pump replacement does the trick (assuming I don't have a bum pump as a spare) then at least we know it's in the pump. Taking a pump off is a royal pain in the back side. I'm a mechanical engineer from Purdue and the guy that designed this arrangement should be shot! Probably a Rose grad. :hide:

[can whlvr 993]

good luck guys,i had a sundstrand from a c 160 rebuilt a few years back,i tore it apart and found it was fairly complicated and a bunch of parts broken,so i broke down and had it fixed professionally,and it works like brand new(it should for what it cost)but im glad i did

[wheeledhorseman 574]

Hi Rob

I guess between us we've got to puzzle this out for ourselves . I too discovered the big slot deep in the bore where the reverse check valve is located but as there is no thread in the bore assumed wrongly that it was a blanking plug. The Toro site exploded diagram shows much more clearly than the Sundstrand manual that there is indeed a ball bearing and spring valve behind it. Someone before me had obviously tried to 'unscrew' it without success though it is difficult to see what could go wrong with this apart from a broken spring or a bit of grit (but from where?) stopping the ball from seating.

The relief valve assembly under the rear fender is, I understand, to lessen the impact of going from forward directly into reverse while the tractor is moving. I guess that it was thought necessary on a D series due to its mass and therefore momentum being much greater than smaller tractors. I believe that this extra was dropped in later production of the D-200 so it couldn't have been that vital. Being connected between the two circuits I guess its function is to relieve excessive pressure during the 'jolt' whilst changing direction quickly, there being two valves which operate according to which circuit is at high pressure and which at low (i.e. forward or reverse).

I didn't get time to dismantle the accreleration valve from the motor today - hopefully tomorrow. Let me know if the transplant solves the problem - if it does then I'll have to make a tool to get that slotted plug out.

[shorts 182]

I'm not a trans specialist by any measure, but previous experience with auto/hydro transmissions would lead me to believe that the slotted plug may just need a magnet to pull it out, and maybe a little twist with a long skinny screwdriver to get it moving. I think that you are on the right track looking for foriegn object momentarly blocking a pinhole orfice somewhere in the control circuit.

[woodchuckfarmer 333]

I had a ford/jake 1966 that had a sunstrand hydrogear in it . It would stop moveing up hill. there was two large nuts(1 1/8 i think) that had a valve assembly under them.This valve was in a sleve that had an oring on the out side of it. the oring was partly gone. I replaced it and the tractor worked fine. to pull the sleve i used a welding rod with a small hook bent in the end. i had to do this about every 2 years . I never did figer out why this happend every so offen. It was like the oring just washed away. I hope this helps you out. This was just my problem with a hydro trans . Good luck.....woodchuckfarmer

[wheeledhorseman 574]

Wooo-Hooo! I think I've found the problem . It doesn't pay to cut corners - I only removed the reverse acceleration valve from the hydro motor (because the tractor doesn't go backwards). I managed to dismantle the valve but the tiny pinhole was perfectly clear. If I had removed both valves to start with then I might have found the problem sooner.

The spring that sits between the two valves has broken into four pieces! Yes there are four pieces, two sections of spring have wound themselves together. This little spring in the hydro sure must take some punishment!

Problem now is where can I get a replacement spring?

I don't suppose Sundstrand have an outlet for spare parts here in the UK so I guess I'll have to get at US stockist to ship me the spring. Any ideas who to go to?

[wh79d160 52]

I bought a D a few years back the the P.O. claimed he had just had the hydro rebuilt in. The company he wrote in the manual is L J Fluid power Inc. in Delton Michigan. The Ph # is 269-623-4150. I'm sure if they rebuilt it, they have parts or can tell you where to get them. I'm sure Kelly or some of the other guys up that way can verify. Good luck. I've found thru the years, most guys aren't very comfortable working on these enough to openly give any iron clad advice. Cross your fingers & say your prayers. :hide:

[shorts 182]

it looks like a spring inside a spring, also looks like a broken piece of spring peeking out of the small orfice in the left hand spool, you need to make sure that you find all of the pieces of the springs, they are hard and brittle so they have a tendency to shatter instead of just break cleanly in two.

Search online for the latest/newest most current part numbers and service bulletins both Sunstrand and for your trans by part and serial number to get the correct replacement parts.

[wheeledhorseman 574]

I've found thru the years, most guys aren't very comfortable working on these enough to openly give any iron clad advice.

I know what you mean Tom, I scoured the transmission forum only to discover that there are very limited responses made to hydro issues. Ok, so hydros are a bit of a mystery, even a bit scary to work on, but that was the case when I got my first car (automobile) way back in the 70s and had to take the engine to bits to fix it. Most of us think nothing of stripping an engine down confident that it will run again so why are we so wary of the hydro?

Rebuilding the hydro pump or motor is perhaps best left to a specialist though having taken some of the externally accessible bits out its amazing how confidence grows and the cost of a new spring (when I manage to source one) will be nothing compared to the time and cost of getting the whole transmission rebuilt. So guys, if you have solved any hydro issues please do share what you have found. :hide:

[gzx3sc 0]

Andy, how did you get the deep plugs out? Are they threaded? I replaced the pump on mine and the problem is solved but I'd like to fix my old pump. Glad to see you made major headway. Once I know how to get the plugs out, I'll take mine apart and see if the problem is the same. If so we'll know how to respond to the next poor chap that looses reverse. :hide:

[shorts 182]

The bigest issue with working on all hydrostatic transmissions is that the internal clearances/tolerances are very tight/close and critical to proper operation. for all practical purposes their are no internal seals or o-rings, it's all ID/OD machine tolerances with the oil itself being the seal, consequently precision measuring tools and cleanliness are important to sucessful repair/service.

It takes a completely different mind set and approach to be sucessful, start thinking along the lines of clean room assembly, no dirt or dust, no grinding, no rags,lint etc, all parts have to be absolutely clean and within tolerance for a chance of sucess.

The other thing is availability of current technical information and parts, all of the paper printed info was generated pre production/release and finding the updated info can be a challenge at best without a direct connection to the manufacturers data

[wheeledhorseman 574]

Andy, how did you get the deep plugs out? Are they threaded?

I didn't get that far Rob before discovering the broken spring which sits between the forward and reverse acceleration valves in the hydro motor on the transaxle rather than the check valves in the pump. My problem appears to have been with the motor and yours with the valves in the pump, both are listed as likely culprets in the Sundstrand manual. The diagram below shows the design of the valve (ball and spring)and retaining cap or 'deep plug' (44) in the pump. It appears to have a threaded shaft that holds it in and applies pressure to the valve spring.

The bigest issue with working on all hydrostatic transmissions is that the internal clearances/tolerances are very tight/close and critical to proper operation. for all practical purposes their are no internal seals or o-rings, it's all ID/OD machine tolerances with the oil itself being the seal, consequently precision measuring tools and cleanliness are important to sucessful repair/service.

Message read and understood Paul. I try to be scrupulously clean when working on the internals of engines as it only takes one speck of grit to ruin a bearing shell or score a cylinder etc but I've been trying to be OTT clean on this job though I can't realistically achieve clean room with filtered air etc.

I am in the process of ordering a replacement spring but it will take time to cross the Atlantic. There's plenty of other work to do on the tractor to keep me busy but I'll put up a post when the new spring is installed.

[can whlvr 993]

thats great it is just a spring,could have been alot worse like mine

when i opened mine up i found a broken retainer ring,and some other parts were needed and one small part made at a machine shop,im very mecanically inclined but this was too much for me,i tried though just decided i wanted it to work right and last

[wheeledhorseman 574]

I quite understand Don. I mentioned earlier that I would get a pump or motor rebuilt professionally as well. Thanks for the photo though, with 360+ views already there are obviously guys out there interested in all this and it's becoming a good thread. So any more hydro faults and what was found to be wrong (even if you got it fixed professionally) would be great. Meanwhile I'm still trying to sort out a source for the spring. Hydro rebuild places use proprietary springs of which they obviously have an extensive range on the shelf. I found one in my spring box that was the right diameter and compressive tension but it was too short by about a half inch :ROTF:

[wheeledhorseman 574]

Got nowhere trying to get a spring from hydro rebuild people but the comment I got from one re the fact that proprietory springs are used led to me discovering that, like bearings, compression springs come in standard imperial and metric sizes. Using a mircrometer you measure the diameter of the wire the spring is made from, the OD of the spring, and its length. In metric mine came to 1.14mm x 7.62mm x 50.8mm. The diameter of the wire had to be measured well away from the fractured ends where it was clearly distorted. I put the numbers into the 'search for a spring' on the Spring Masters website and sure enough it's the a standard spring . (Spring Masters are a UK spring manufacturer but I'm sure there are similar outfits in the US). As one would expect it's actually an imperial spring, 50.8mm = 2 inches. As a double check they give the number of coils to the spring which I checked against the original having sort of pieced it together and the numbers matched. There was a minimum order value so I've ordered 10 as you never know when I might need one for my C-120 or someone else might need one. So progress is being made but I'll have to wait now for them to be delivered.

[neil 2,410]

lets hope that this will solve your problem Andy and that you can (SPRING) into action when its repaired GOOD LUCK

[wheeledhorseman 574]

Rob, I finally got round to fitting the spring that sits between the forward and reverse acceleration valves in the hydo motor. I haven't had much time to work on the D-200 in recent weeks so it had to wait till today.

Despite being obviously broken, and therefore I doubt the acceleration valves were actually doing anything useful, it turns out that this was not the cause of having no reverse. So it looks as though I'll have to make a tool to turn and extract the deep plug in the pump to check the reverse check valve there.

I started taking the panels off today to get full access to the pump. What a pain! To get the foot plate off, first remove the fender. To remove the fender, first remove the fuel tank and so on. Doesn't matter really as I have to take them all off for painting anyway but it would have been nice to have been able to crack on and see if the problem is with the valve in the motor.

It looks increasingly as though the fault I have may be the same as yours i.e. in the pump. Everything works fine except reverse. I'll get there though! I have to as I don't have a spare pump! On the bright side, I've fixed what was certainly a fault with the motor acceleration valves and which could perhaps led to the failure in the pump. In saying this I'm mindful of something you said at the start of this post.

It also won't hydraulically slow down when going from forward to reverse.

I'll keep you posted with any further progress.