I have a 4YS serial number 938G. The trans sometimes will not come out of forward, I can put the shifter into N or R and the loader will drive and shift forward. There are no fault codes on ET. I wiggled the steering column and the fault would appear and disappear for a time but would eventually stick in forward, the same with the parking brake if I moved it up and down the fault would come and go so I changed the switch on the back of the parking brake and it made no difference. So I am back to this intermittent fault, when the trans is working as it should it shifts strong in every gear. I thought it might be the spoolsticking in the tranny but that seems unlikely due to the wiggle and parkbrake scenario. Any one come across this before, I don't really want to start tearing a loom apart. Thanks Gary.
I would need to dig a little deeper into the system to be sure (no internet right now) but from the symptoms you are describing my first thought would be a harness fault in or around the steering column - especially in view of your comment that wiggling the column makes ther problem go away temporarily. I'll have a closer look when I get back on line and post with more info. Meantime if you want an electrical schematic then send me a PM with your exact Serial Number and your e-mail address and I'll fire one off to you.
Just a couple of thoughts to get the discussion going. First of all this is an ECPC controlled transmission. Simply, it is controlled by the PCM depending on inputs from you. Obviously if it is staying in gear (forward) then it is not receiving your input from the switch in the F-N-R handle and it is maintaining forward clutch pressure (typically clutch #2 in this machine) through the proportional solenoid that controls this pressure. My guess is consistent with Niges assessment, you have an open or intermittent in the harness or switch in the FNR handle. Because the switch is on the input side (correct me if Im wrong Nige) the PCM will not see an open, it does not send a pull up voltage to the input side to check circuits, only sensor side.
It has a new shifter on it and still the same, will tear loom apart I guess. Thanks everyone for the input so far.
Would you like a copy of the Electrical Schematic..? If so send me a PM with the machine Serial Number and an e-mail address. I can send one to you right now because I'm working today.
Thanks Nige I have the schematic and will keep y'all informed of my progress today.
Maybe take a look at any/all the harness connectors to the shifter control loacted around the steering column and inspect for corrosion/contamination in the pins/sockets would be a first step. Next would be a "Wiggle/Pull Test" to check the resistance of each wire in the harness related to directional shifting while attempting to forcibly separate the harness into its component parts (2-man job). I don't know if it's relevant but depending on the Date of Manufacture of your machine there was a Service Program "FOR REPLACING THE TRANSMISSION SHIFTER IN CERTAIN IT28G, IT38G, AND IT62G INTEGRATED TOOL CARRIERS; AND 924G, 928G, 938G, 950G, 962G, 966G, AND 972G WHEEL LOADERS" dated 19/07/2002. I can't see too many details but I'd bet it was a Before or After Failure Program that may well not have been applied on your machine if the originally-installed shifter did not fail before the Program Expiry Date. There are 3 generations of Part Number for the shifter control - 130-6260 -> 201-0211 -> 299-5839. Which Part Number do you have installed..? If it's a 130-6260 it should be considered as "potentially dodgy". The 202- number was introduced in late-2001 and the 299- number in late-2008.
Checked electrics and removed and cleaned vlave body, no apparent issues. Ordered a PCM and will change it as a hail mary and see if anything happens.
Nige**** I have Hey similar problem my cat 938G with a 6W serial number, goes forward in both forward and reverse. If I put the SNR switch in reverse the machine still goes forward when put in neutral the machine does not move as should and forward it goes forward. Please help
I assume you mean 6WS-prefix for the Serial Number.? You're going to need the electrical schematic for a kickoff. There are two so to get the correct one we need to know if the Serial Number is above or below 2578.
Also I suggest that you take a look at the F->N->R control and try to find a Part Number on it. See post #7 above for three possible Part Numbers, at least one of which should be considered as "potentially dodgy" reliability-wise.
6ws00902 938G . Serial number and model
Also I noticed that my forward solenoid top left of control valve . Has 4.5 volts ign on in neutral same with reverse 4.5 volts ignition on in neutral .
Should be dead either way. Are you measuring the voltage with the solenoid valve connected to the machine harness.? If you had it disconnected then you will need to reconnect it and back-probe the connector to read the applied voltage. When you finish that, pull the electrical connector from that same solenoid valve and measure the resistance of the coil. It should be 31 +/-3 ohms. Post back with your findings. Also dig into the transmission speed/direction control and get the Part Number.
Nige thank you so much !!! can you email in to me I am having trouble opening your file .. [email protected] . TiA
It's nothing special, only a pdf file. Try opening it on a PC. A smart phone won't show it worth a damn.
okay nige so the previous owner told me that he had the valve body off because it was engaging hard and when he put it back together , the machine now travels foward in both foward and reverse. im thinking he may have gotten a selector backwards. are there any good diagrams as to how reverse selector spool sits in the valve body .? please and thank you.
Penny just dropped............We now have two threads going for the same machine - not good. Here is the other one. First up, get the P1 & P2 pressures and see what the results are, then we can talk further.
Okay so I pulled pressure P2 = 0 psi when machine is started also when put in reverse and cycled through all speeds . P1 has 50psi then when shifted into forward it drops slightly then returns
If those pressures are correct that machine will not move anywhere. P2 is the direction clutch pressure. Based on that I cannot reconcile your statement that the machine moves forwards whichever way you shift the direction control. It should not move at all.
i will check once more and report back. thanks
Did you follow the procedure I posted (post #8) on your other thread.? Are you sure you got the gauges on the correct test ports.? Also can you see now why having two threads for the same problem is confusing.?
Yes I see this now . And I’m 100% sure that my guage is on the right test port . It’s too right of valve body (p2) . P(1) is on the bottom of valve body . I checked again today I have 0 psi at test port p2 and it goes forward . Previous owner said they had valve body off
Refer back to the test procedure page 5. Put a test gauge on port marked G that is located on the transmission filter housing and measures pump pressure. See what that gives you. Note all these readings should be done with the oil warm.
test port g = give or take 390 psi close to 400..... i understand that p2 is the direction clutch . but i **** you not i have 0 psi but the machine moves foward.
Spec's 400+/-25psi so you are on target with that. Ok, so based on what you said before regarding the previous owner removing the trans control valve (and disassembling it) for whatever reason. clutching at straws a bit but what do you have to lose.? Take a close look at the valve body. Take photos and post them here. Are there any other plugs in the valve body that could have been swapped when the valve was disassembled and the test points installed in the wrong locations..?
i will remove the valve body flip it over and take multiple pics he said he replaced the reverse spool and slug . i know zf transmissions worked on kawasaki loaders for years now working for kobelco dealer. but i bought this cat to clear my land thinking i could solve reverse easily but seems like i found myself an abortion the guy didnt mention any of these bogus repairs until after i was knee deep.
Before removing the valve body I would take a close look to see whether or not it is possible for the test points to be installed in a wrong location. See my suggestions two posts up - need photos of the valve body so that we can see what you are seeing.
Okay here is the valve body also when I went out to take this picture I started the machine with guage in test port g . This time guage reads 50- 80 psi . No clue why I got over 300 psi before . But now machine Has been running for an hour and Gage won’t go above 80 psi
Maybe start by draining the oil and remove the suction screen to check it.? That is if you haven’t been in there already.
Before getting in too deep. Would you like to try the pressure readings with another gauge..?
i have a break through .... was looking at the control valve pdf you gave me ... so i took the valve body off ands he had the plastic modulating valve on the wrong side of the control valve and the spring on opposite side . i put back together per the pictures provided, and now i have substanial pump pressure 400+ and on p2 port i have 235 psi or so and when put into reverse it drops for a second then returns to normal prssure same with the speeds it drops and returns ... so now i am lostt.........
At least you are moving forward. I was thinking a bit about your isues earlier today and what came to my mind was "I wouldn't mind betting that this is more than one problem, and the root causes could well be in completely different parts of the machine". So take what you've got so far as a plus - you've found and corrected one issue but a few details need confirming before it can be classed as "sorted". Now read on .......... P1 & P2 pressures will always dip for a split second when you engage any gear forward or reverse. It's the pressure drop caused by the cavity behind the clutch piston filling as the piston moves. In fact if you had two identical gauges you could put one on test point A & the other on test point B and watch the pressures dip & recover together. Your P2 numbers seem a bit on the low side, it should be no less than 250psi because the spec is 275 ± 25 psi. See comments below. What do you have for P1 pressure now.? You never mentioned that. Remember from the spec that P1 should be 42 ± 10 psi higher than P2. Also please do the pressure tests (Pump, P1, & P2) at both Low Idle & High Idle RPM and observe if the results are at all different, even if only slightly. Post up all your numbers. What is the max pressure of the gauge that you are using for your measurements.? Ideally it should be no more than 500psi, and more important still a gauge that is known to be accurate. A gauge of 1000psi max or even higher can lose accuracy at lower pressures.
yeah my guage is 1000psi let me see if i have a 500 max guage ill post back with p1 and accurate readings on p2
ok so found 2 500psi guages... plumbed p1 and p2.... p1 is running around 320-325psi and p2 is 275-280 when engaged to reverese they cycle together nd return to their original pressures ...the pressure doesnt seem to move at all when idled up high
Well that's all within spec. P2 - 275 ± 25 psi, P1 - 42 ± 10 psi higher than P2. So what's the transmission doing now regarding gear selection.? Has anything changed in respect of engaging forward speeds even when the transmission control in the cab is moved to reverse.? Another question. When you select reverse in the cab does the backup alarm sound.?
the machine no longer moves fowrard in reverse . when selected to fowrard the machine will drive in any gear . when put in reverse you feel the torque converter engage with a thud then nothing happens . the back up alarm does sound when put in reverse and when shifted through the speeds in reverse you can feel the gears changing in trans .
Put the gauge back on P2 again. With the engine at Low Idle note P2. Engage 1st forward. Observe the pressure dip and especially note the lowest value it reaches before recovering. You'll need quick eyes or maybe have to repeat the test a few times. Then do the same test in 1st reverse. Is there any difference at all in the pressures you see compared to 1st forward.? Have you ever removed the suction screen on the bottom of the transfer case to inspect for particles.?
the screen was completely clean of particles ... i will go out and pull p2 again to compare forward 1 and reverse 1. i did notice that it take a few cycles of the f-n-r switch to engage the transmission in foward and same exact symptom with reverse the back up alarm comes on every time you move the fnr switch to reverse but i will only feel the torque coverter if i move it back and forth from N to R a couple times. figured its just getting worn out and prolly not my issue for no rverse cause i do have my solenoid power and torque converter engaging,
While you are into it, do you have DMM lead attachments that will enable you to back-probe the wires to the solenoids.? Try taking the voltage readings on the FWD (#3), REV (#2), & 1ST speed (#4) solenoids, but as above it will only give you good results if the solenoids are connected to the machine harness while you are doing it. Measure the resistance of the three solenoid coils while you are at it. The specifications are in a table somewhere on the electrical schematic. My thoughts - If the F-N-R control does not engage a gear in the transmission immediately that it is moved from N to F or N to R it has to be considered to be somewhat suspect. You might jib at the cost of a new one though, IIRC they are somewhere around $1400.
ok nige so i tested the prssures again P2 AND P1 look identical when shifting into foward reverse vise versa. also ohmd out all coils 29.5-31 ohm 2 and 4 do power up together when shifted into REVERSE 1. it seems odd to me that when i engage the machine to reverse it lunges foward but does not move after the initial lunge
What voltages did you measure on the 3 solenoids.?
and yes i did back probe the solenoids.. also forgot that when p2 pressure drops for either forward or reverse the guage goes to zero then returns for both gears
Pressure drop to zero is a bit surprising. Uusally it only drops 100psi or so. Did you confirm that the correct solenoids energized simultaneously when selecting 1st FWD or 1st REV.? What voltage did you measure on each solenoid when they were energized.?
the solenoid had 23.4 volts and yes the coreect solenoids were energized simutanously
I think that "clunk" you hear when engaging reverse is nothing to do with the torque converter, because if it was you would hear it when you engage forward speeds also. The torque converter is working all the time the engine is running. I'm still not happy about the fact that you apparently have to jiggle the transmission control more than once to get any gear to enage, but despite that voltages at the solenoids and correct coil resistances seem to indicate that power is getting to the transmission clutch control valves. Have you tried switching the #2 reverse solenoid valve with one of the others, maybe #5 or #6.? If that doesn't work then my opinion is that something is likely broken inside the transmission on the reverse clutch countershaft. The power flow down through the transmisison goes via two totally different paths depending on whather the FWD low clutch (Ref #4) or the REV clutch (Ref #23) is engaged.
I know that the above is probably not what you want to hear, but in the absence of actually being there with the machine it seems as though a process of elimination has brought you to this point. As I said above, I'm still not happy with the operation of the cab control, but there seems to be nothing else left as an option but an internal transmission problem. Rather you than me take the decision to pull it though.
im gonna pull it bud .. ive built a lot of zf / funk style transmissions .. what exactly will i be looking for with the reverse pack?
I'll be honest I think you will find a mechanical failure somewhere either on that shaft or in the gear train that drives the reverse clutch basket. I think that's what the bang or noise or whateve rit ius when you select reverse is related to. The fact you have P2 at specified pressure when you select reverse means that the reverse direction clutch is engaging fine. Just FYI "The Book" procedure is to remove the engine & transmission/converter as a unit, then split them once you have them on the floor. I'll send it to you.
An update. The OP pulled the transmission and on disassembly it was discovered that the fwd high clutch basket was in two pieces and the discs/plates of the clutch itself were welded together - probably what broke the basket. The broken clutch basket was probably also related to the "clunk" he stated that he could hear when selecting reverse.
NIGE would you mind sending me the schematic? Having concerns with mine as well, but not sure if it's wiring, controls or operator error. i have to shift the forward and reverse lever twice in any direction to get it to respond. once it does respond, machine moves with no issue, except that shifting between gears 1,2,3,4 seems intermittent(not responsive) serial - * CAT0938GCRTB01915*