I have now posted the requisite three replies and can get to my question. Is there a trouble shooting shop manual that will help me figure out what is wrong with my loader's transmission? I have a Schaeff 831 loader with a Perkins engine and Bosch Rexroth hydrostatic transmission. It should be a better machine than it is. What it does: Does pretty good in forward but is horribly sluggish in reverse. Before the "repair" mentioned below, it was the opposite. I avoid going down a slope for fear I won't be able to back up it, the diesel motor makes a serious effort but there is no power to the wheels in reverse. It will however, spin all four wheels in forward against a load. If I run it in high range it will go forward OK (not great since I like to GO) but will hardly get out of its own way in reverse, I have to downshift then upshift in reverse. I have spent $1700 for "repairs" by a heavy equipment shop in Fort Smith which for now shall remain nameless. They pulled the drive motor and pump, bench tested same and said all was good...it isn't. At least something isn't and I suspect it is some kind of control or adjustment. I checked it as best I could at the shop before loading it and bringing it home. I faced up to a 20' dumpster full of scrap on their gravel lot and shoved the dang thing all over the place. Terex bought Schaeff and they don't have shop manuals for this machine. Lawyers have prevented them from offering any help it seems but I did manage to contact one helpful fellow in Germany who sent me some specifications and an owner's manual. Rexroth have all kinds of general information including detailed specifications on pump, motor, some of the controls and inching pedal as well as fundamentals of operation for the type of system (though I have no idea why they have a swash plate pump driving a swash plate motor, guess it has something to do with torque). But they do not offer a shop manual or trouble shooting guide, if they did I would be happy to buy one. I keep thinking and hoping that the problem is something simple like an adjustment. One of you in this forum has to be an expert on this and able to supply some helpful direction.
I'm not an expert on exactly this type of equipment. But we have had Liebherr dozers for many years by us. And i have some hours both with the wrench and in the classroom... The hydrostatic ones. After your description it looks like your loader is not angling the pump or drive motor correct when u put it in reverse. I bet there is some problems with the system angling the motors when u put it in reverse. You don't say anything about the controll system for the motors. Is it electrical or hydraulic? And i mean how the motors is angled/controlled. And u don't say anything else on the topic to help us solve the problem. Is the high and low a gear in the drop box? Or is it done by the pump/motor? There can also be a problem with the return line restricting the flow when u go in reverse.(Valve) I bet the best help for u is to get in contact with some european guy who repairs this type of equipment... But, give us some more info, and i bet som others also can give some good advise on repair and foult finding.
Welcome to HEF cherokee101! :drinkup
Well...I wanted to see what kind of response I got before going into more detail. I need to get the system particulars such as motor and pump model to go a lot further and, not being in the right place now, I can't. But for starters, this thing is electric over hydraulic. There is an electric switch / shuttle lever on the dash for direction control and a rocker switch on the dash for hi / lo speed control. Direction is linked to a couple of servos on the pump linked to a hudraulic shuttle. The motor swash plate is controlled by pressure operated hydraulic valves in respons to load. Bosh Rexroth tells the story of their system as though it is common in many applications around the world including US. Well, stay tuned for more particulars and we shall see where this little trip goes.
Never worked on that paticular machine but i have Had head scratching moments with Rexroth Hydrastatics. Try swapping the control solinoids about. I.E Swap the solinoids from one side to the other on both pumps. The Solinoids in question. (One arrowed for clarity) They control the swash plate throw. You can Remove the Whole lot or just swap the the wires around. This will Elliminate Either the pumps or electrics. Ross
These systems seem unnecessarily complex but they are what they are. I'll give that a try. There is some kind of interlink on the brakes as well and I have wondered if that is hanging up. Just a service manual would be a huge help. It would also help a lot if I would educate myself on how to ready a hydraulic schematic. Thanks
If the shop thinks the pump is good I'd tend to believe them. When I first read your post I immediatley thought control circuit. I think Ross is on the right track with troubleshooting by testing individual circuits. The Bobcat AHC system would do the same thing when it got full of dust...the electric components would make the controls go berserk...or not work at all. To test this theory you need to be able to operate the directional shuttle manually and then test the machine without the electrics interfering. This could be dangerous!!!..not to the machine but people and objects in the area That aside it will tell you if the hydraulics is working properly....as does Ross's method of switching over the solenoids on the shuttles ....or even just the wiring, although a dodgey solenoid will then affect forward not reverse. Good Luck
Thanks for the replies. The shop bench tested the motor and the pump and said they are good. I know they at least took them off because the bolts and seating areas show as much. Hydraulic fluid tested as good for a machine with 6500 hours on it. The machine has been treated badly but the pivot pins and bushings on the articulation as well as the loader are in really good shape, just not much play at all. Reverse in particular seems like it has to wind up to speed and then it is not as fast as forward so I suspect, as do you, something in the swash plate control either electric or hydraulic. Now, in fwd or rev but more in reverse, it takes a whole lot of engine rpm to wind the thing up to go. As I manage to read the bosch promo literature this system has a hydraulic load sensing feedback loop that prevents engine stall by unloading either the motor or pump swash plate in response to increasing pressure (LOAD). You can sure feel this take effect as in when I went across a boggy pasture or up hill the thing slows down a lot and it does a good job becasue the engine sure doesn't load up. I think this transmission is not working properly but I also think it is designed for a specific job outside what I may ask it to do. That job being to work on relatively level surfaces, load the bucket with a lot of force but low speed and cycle to dump. Hydrostatically and automatically downshifting when the pile is hit with the bucket. Just irritates me that I can' pull the hill between farms without downshifting to creeper gear and having that engine roar with such sound and fury signifying so much so close to nothing. I had visions of this machine being a more comfortable, higher lifting capacity and non-turf tearing skid steer but it doesn't seem to want to be that. It may belong in a landscape dirt and mulch yard because it'll do that work well. Being a tool-carrier loading hay bales and woodlot cleanup and clearing with a brush rake and grapple may just not be its thing.
Loader info Is this Loader C/pivot with the engine transverse, poss a Perkins Phazer??? I had a pig of a game with one I also have a few pics the traction pump drove into 2 motors on the drop box that is bolted to the rear axle, I think it must be the only one left working in the U.K. 2 questions have you checked the oil tank and filters /fitted new filters. did it just start to play up for no reason, tctractors
These things seem to be common on the European Continent. Yes, it has the center pivot, transverse perkins engine a traction pump, aux pump and a bent housing motor on the drop box / transaxle. It didn't just start to act up but it was pretty much like it is when I got it. I had problems getting it up the ramp onto the trailer in high range. When I had the motor and pump checked I got it back and it had lots of power in forward, sort of, and had the previous forward problem in reverse. I have checked the fluid level but have not replaced the filter since I don't know where to get one.
I may know your fault Today cherokee I had to sort an Hydraulic drive fault with a Schaeff SLK 871 loading shovel, this is a rare banger to find in the U.K. anyhow the fault was the thing would hardly move in forward (gone progressively slower over an afternoon) but would run as normal in reverse, on the Rexroth pump where the high pressure pipes come out of the pump is a pressure control valve at each end of the block, on the top of this block about directly above the high pressure pipes is the pressure test points (mini-mess style couplings with plastic caps) the first thing to do is swap over the pressure control valves to see if the performance in direction is reversed, (improved forwards or reverse) I think an 1.1/4 A.F. spanner will fit these valves and only a small amount of oil should spill out when the complete valve is removed, if this swapping of valves shows any difference in it's drive, then you will know this is the problem, the valve to the rear is the forward pressure control the valve pointing to the bucket is the reverse pressure control, strip down only the faulty valve, it's most probably the PTFE type O ring fitted on the piston plunger (the outer most part you unscrew) if you carefully hook a small pick under this seal and remove it ( underneath this seal is a rubber O ring do not remove this) you can turn this seal around and refit it onto the barrel then screw it all together and away you should go, you should reset the pressure to the same as the other valve, I can tell you the method if you need it, finaly all those swash plates are there because the loader has 2 speeds??? If this helps you sort your loader your cost is " NOTHING " as you dont even have to buy an O.ring All the best tctractors
Filters In the 871 I changed 2 filters both under plastic caps in the hydraulic tank,the one filter for the traction drive blocks easily (it filters from the inside out). tctractors
Fan Dang Tastic! Most interesting fix. It makes sense, warms up, o-ring creeps, seal not effective, bleeds by and no power? That is a little cartridge valve isn't it? I am most anxious to tie into the machine when I get to the farm. I have my dental pick ready to tackle the problem. I was afraid to open the hydraulic system for fear the oil would all pour out. Swash plate if for that funnly load sensing process and anti-stall plus the two speed tranny. That might make sense also, the motor swash plate moves for the two speeds and the pump swash plate moves in response to pressure to prevent engine stall. I'll check that filter as well. I will investigate with renewed enthusiasm and let you know how it turns out but it will be after Christmas. A very much appreciated note today! Thanks.
Valve. yes cherokee it's a cartridge style pressure control valve, it has 3 hexigon nut sections the piece with the PTF O,ring on is the smallest hexigon section , if you look at its surface the leading edge will be worn off, pick it off carfully, then turn it 180 and refit it onto the plunger , squash the O,ring back into shape with your fingers,then carfully refit the plunger into its cylinder,a small screw-driver prod about will help ,to reset the working pressure you will need a 6'000 psi clock and a union to fit the test port (or the quick coupler pipe) then stall out the drive in a bank of dirt, measure pressure on good forward valve (about 5'000 psi) swap over valves and stall out forward drive again with bucket in a bank of dirt and adjust the smallest hex part on cartridge with an allen key in the end, the electric side of the transmission is very simple, the mag valves on the pump are forward /reverse the other mag valve is high /low the 871 is 24v, the best way to test them is with a screw driver in the centre of the coil where the post would go and see if they are magnetic when energized with the correct voltage I need a Beer tctractors
TCTractor: I've spent a good deal of time digging on the Rexroth system, I seem to find no joy in talking with anyone about the situation. I found a number of references you may find interesting / useful and have taken the time to attempt to understand more about the system present on the drive train of the SKL / Terex Loader. Rexroth has some fair product descriptions here: http://www.boschrexroth.com/various/utilities/mediadirectory/index.jsp?oid=254241&language=en-GB Expand or go back to find what you are interested in. When you decode your product identification the machine becomes a little more clear. I found an online part catalog here: http://www.flinthydrostatics.com/ Just go to the Rexroth pages and find your pump / motor. When last we exchanged messages you suggested turning over a seal / O-ring. I have not managed to do that for reasons not worth going into. However, I seek additional explanation to be sure we are talking about the same things. I believe we are speaking about item NO. 20 in the drawing that I've had to attach since I can't figure out how to make it easy for you by pasting the diagram here. This is a High Pressure Relief Valve, one for each direction.
Ross: Can you explain how you were able to put pictures in the message? I can't find this on FAQ
Go to the 3rd post in this thread. Countryboy has a link to very good directions on inserting pictures. You have to look below his 'signature" There is a free resizer that you can download, and it works really well. I was surprised.
Very good, thank you on the posting of pictures.
Right Part, cherokee No 20 is the correct part, if you work out which one is knackerd , they can be swapped just like the hydraulic shop did, then follow my previous script you will soon have the loader " Blowing on all Six " all the best tctractors
TCTractor: Boy am I learning fast! This hydrostatic transmission stuff is pretty neat. Once you get the schematics and exploded diagrams in hand the mystery begins to be revealed. It isn't easy but quite elegant actually. Fluid logic! A few years ago I did trouble shooting on a subsea hydraulic system, found out it was not pressure compensated and some plugs were left in that should have been left out. Worked perfectly on surface but just chattered subsea. Headed to buy a pressure test kit soon. $200 to $300 should get what I need I think and I can work on the dozer, trackhoe, loader, tractors and not hunt and peck so much maybe. Found a source for the seal kit for this deal. Seems pretty pricey for O-rings at $293.00! Think I'll try your solution first. I have heard that some folks have managed to split the case of pumps / motors by arbitrarily increasing the relief valve pressures! I can't figure out why the shop didn't check pressures. I sent them all the specifications of set points that I managed to get from Schaeff / Terex in Germany. I'm no expert but I think I can know about as much as those folks do in pretty short order and put my $2000 in repair costs to them to better use. Every time I break down to go to the "experts" I am usually sadly reminded why I was doing things myself. I think all the sorry devils did was to reverse the HPRVs...if they did that! Also figured out how to adjust the neutral point so the machine won't creep while out of gear. If I get this solved it will make the little Perkins worth spending some time on, it needs some help. Thanks and I'll post again when I get the chance to give this new knowledge a try. If it "blows on all FOUR" I'll be a happy camper! My kid brother will have to eat his disparaging words of my little machine I hope.
The beat goes on. Discouraged and I have not even turned a wrench. Spoke to a guy yesterday who seems to know what he is talking about and he just about has me convinced that the pump or motor or both are shot. Fluid heats up, performance drops = drop in viscosity = high pump or motor leakage = drop in pump or motor performance. It is getting long in the tooth with 6000 hours, not by me, and a lot of apparent neglect, also not by me. What should a rebuild on an A4VG40DA1D4 32R-PZC02F015S Bosch RexRoth Pump and an A6VM80DA 60W0290-PZBO 20B Bosch Rexroth Motor cost? I just want to brace myself somehow and start saving my lunch money.
The End. This World is full of doom and gloom sorts, at 6,000 hrs your shovel should just be about run in and going well, Rexroth make great pumps that are simple and robust, easy to work on as I have often stripped them on site in all weathers, get your spanners out and have a go ???? tctractors.
Yes, nothing ventured nothing gained. Spanners in hand.
An update the the continuing saga. The problem has been largely fixed. For the help of others as uneducated on this subject as I: Inspection of the pressure relief valves showed one to be pitted / eroded, this has been replaced. Finally laying hands on a Rexroth service manual (excerpt only) concerning said pop-off valves we find that the external jamb nut and socket head screw on the forward and reverse side of the pump are for the TOW MODE BYPASS only. Turning these in six turns will open the pop-off valves allowing for limited towing while bypassing the pump. They are NOT for adjustment of the relief pressure, as both the previous owner and I had assumed. Upon further inspection one was found to be turned in 1.5 turns and the offending valve (the eroded one) was turned in 3 turns! Backing both screws out all the way resulted in an unbelievable increase in performance ...duh. Adjustment of the pressure relief cartridge valves is accomplished by backing out a socket head lock screw within the spring assembly and turning a small bolt. All this adjustment is internal and must be accomplished with the valve on the bench. For this particular machine / pump the pressure adjustment is approximately 620 psi per turn of the adjusting screw.
Valve . Yes thats the correct valve, swap them over and the fault should transfer, dont forget to vent the hydraulic tank before you start with spanners. tctractors
Could you please post the Rexroth excerpt you found? Doc
I'd be happy to but it is 2.4mb and this site only allows 100kb and won't let me upload it. Want to mail me an address and I'll send it to you?
WTH are you doing in Nigeria? I've been there and done that and am a little leery of anyone claiming to hail from there.
Yes-0 I'm out here in the jungle looking after the maintenance, repair,and training for a large construction project. 3 years now......a 10 year project, glad to be here away from the finincal crisis in the USA. Africa never had an economy so not much different here. My email is [email protected] would appreciate the info you have. Doc