Hi all, Trying to sort out an overheating transmission on a D6H Serial No. *2KD00564* for a buddy. The history of the machine as I’m aware of it is as follows: He bought the machine, put it on his lowbed, and when they tried to offload it, catastrophic clutch failure in the transmission. Someone changed the clutches, the cables and the transmission pump. Now, it’ll go about 150 metres, and just stop. Transmission getting very hot. I measured oil cooler inlet pressure at the filter cover, and I think it’s supposed to be 98psi, and I’m getting a reading of 580psi. Am I correct in thinking this would indicate a blocked oil cooler? And if so, what else do I need to check/clean/flush? Thanks
Normal recommendations after a major transmission clutch failure are to replace the transmission pump and the cooler, then sponge gun all the hard lines in the powertrain oil circuit and finally run the machine for a while after recommissioning with cleanout filters installed to collect the rest of the cr@p that the aforementioned procedures didn’t get……. Have you pulled the magnetic screen for the transmission pump suction to see what’s in it.?
I’m intending to pull out the oil cooler and the magnetic screen on Monday, and I’ll update you on what I find in there. Would you mind elaborating on the sponge gun procedure please? Not too familiar with that. Thanks!
See attached. Look specifically at 233-7191 & 233-7192.
Much obliged, thanks
That’s by no means the only way to clean out the inside of hoses, it’s just the one I’m most familiar with.
measuring pressure from the oil filter will give you main pressure not cooler inlet pressure. If you have a heat gun check temp at inlet and outlet and see what you get. there is a little plastic valve in the valve body that gets damaged and can cause a rise in trans pressure.
Ah okay, I thought the T&A said tap E was oil cooler inlet pressure. Whereabouts can I find this valve and check it? Also, if what I measured is main pressure, is it within range? Thanks
Come to think of it even 580psi (which as Dave says is pump pressure) at the filter head is way too high. The spec is 420 +/- 15psi. It sounds as though something wasn't cleaned when the transmission was overhauled and that you have a valve sticking somewhere. Either something inside the transmission control valve (was it ever removed and cleaned when the tranny was out.?) or the priority valve maybe.?
3t7727,7G9476 Don't recall witch one but if they look damaged replace
3T7727 replaced by 9W9830. See SEBD1972 attached. Also needs a 5H8853 Seal to install it. TBH our SOP when overhauling a transmission control valve was always to replace those plastic orifices whatever they looked like.
Thanks for the info guys, I’ll check the valve and revert.
Just to confirm, as I haven’t done this before, is getting the valve out a transmission-out job, or can I take it out with the transmission still in the machine?
Transmission has to come out. If the valve was not disassembled and cleaned when the transmission was out before. I suggest that you do it now. If it was, then make sure that it was put back together correctly.
Okay. Is there a procedure I can follow to get it out and disassemble? Thanks
I thought you had a service manual.?
I wish I did, but no just random screenshots off the internet.
I have been able to remove valve body by taking the plate off the back and removing the tubes I think the orifices are in the middle section it is heavy and tight but can be done
So I’ve taken the plate off. Do the tubes come off upwards? Open up the big nut that’s on the outside and then upwards?
Yes you have to remove the 2 big nuts. There will be a spring holding the tube in. If you don’t have a winch you can pull the valve out the back through the hole. Sounds like a valve assembled wrong or sticking. Also you don’t mention the torque being rebuilt so you will probably be looking at that too. If you truly have 580 at the torque there will likely be damage to the inside metal seal rings.
I don't think he does because the oil cooler test point shown in his screen shots above and in the T&A (attached) is wrongly labelled. I think it should be pump pressure because it is right on the filter housing and according to the schematic on Page 13 of the T&A the filter is the first component after the transmission pump. It still begs the question as to what pressures are in the rest of the system if he is measuring 580psi as the pump pressure when it should only be an absolute maximum of 440psi (425 +/-15).
Okay brilliant. I’m going to give that a shot first thing tomorrow morning.
Thank you! I’ll measure pressures as per this T&A and revert.
So just a small update: I’ve managed to get the control valve out. Opened it up. Orifice 12 is there, but 34 is not. Seems like maybe someone just decided to eliminate it. Could this be causing the pressure variance?
And loads of sludge in the bottom chamber of the valve
Also, there are two holes, whereas there’s only one on the diagram where Orifice 12 should be. So are there two orifices?
Part number at the bottom of the valve assembly is 8G8548 and on the valve block itself is 7G9568
That's the parent number of 7G9569 which is the Body for the Selector & Pressure Control Valve. No, there will only be one. When you get the replacement it will be obvious which one of the two holes it fits in. Offer the valve #10 up to the manifold #8, it may be the case that one of the two holes in your photo does not have a mating hole in the manifold and therefore serveds no purpose. So it looks as though either nobody disassembled the valve, or maybe they did and got the reassembly wrong. Either way I would say that you ought to go into it now to check that it is assembled the way it should be. Additionally, I suggest that you pull off the pump suction screen that lives behind a 4-bolt cover and also the screen #28 that lives in the torque converter drain (circled). You WILL need the transmission oil drained in order to do this unless you want a bath. Then you can turn your attention to the transmission cooler. As a minimum it will need to be removed and cleaned. You'll need a load of new gaskets and seals for the reinstallation.
Thank you so much! Pulled out the pump suction strainer, had a fair few particles in it. Avoided the bath by draining the oil first! Pulled out the oil cooler as well and sent it off for cleaning, but will probably look to replace depending on parts availability. Ordered the orifices, so hopefully should get those tomorrow morning, and then just give it all a good clean and put it back together.
Photos.? Did it appear as though anyone had removed it recently.?
No it doesn’t seem like it’s been out since before the failure.
Ok, so what you found in it is most likely pre-failure. The photo doesn’t show much, it’s what inside the strainer (and stuck to the magnets) in the bottom RH corner of your photo that is of interest.
I’ll take some better photos tomorrow.
There is one thing that’s still bothering me about the above photo though. I know you said one of the holes won’t have anything in it, but since they’re both recessed, doesn’t this mean that even once the assembly is put together the one that doesn’t have an orifice in it will just be open? Because they’re both recessed into the casting on both sides of the valve body, and both into the same cavity.
The oil is sucked from the inside to the outside of the screen as shown by the arrows. Therefore anything interesting, metallic or otherwise, will be found either on the inside of the screen or stuck to the magnets.
Poke a piece of wire or similar down each hole in turn. Can you determine if one or other of them has no outlet.? You'll have to open the control valve up to clean it internally at some point. That point may just as well be now. It will also enable you to compare the parts and their orientation/assembly inside the valve with the parts illustration you already have. Attached is the D&A procedure for the control valve.
Thank you for the document. I’ve got the control valve apart, and both the holes are right next to each other, through and into the same cavity at the bottom. There’s nothing blocking oil flow through either one, so even once the orifice is installed, the other one will be open through right next to it.
So both holes have what appear to be machined seats. So the top one is where according to the diagram the orifice is meant to go. The bottom one is the one that I can’t figure out.
And that’s the bottom of the body, showing where the holes come through right next to each other.
First things first. The screen & magnets don't look too bad at all, especially if they were not cleaned after the supposed recent "transmission failure". I've seen them totally solid with burned clutch material. Clean them well, blow off with compressed air, and they can be reinstalled. BTW is the oil from the photo of the magnets what came out of the transmission.? That is absolutely horrible and should be junked if it has not been already.
Now on to the orifice. Looking at your photos I am of the opinion (and I stress it is only an opinion) that one of those holes, I think the lower one, should have been plugged or had a ball bearing or similar pressed into it in a similar way to the one on the top right. It's a common thing with valve bodies, there are passages that have to be closed to make everything else work as it was designed to do. I just hope someone else can comment on that. As I said previously I think when you receive the orifice it will be obvious which of the two holes it fits into.
And if you look closely you can see what appears in the photo to be the remains of a cap/plug/whatever that is totally separate to the valve body. I have indicated it with an arrow. I think this somewhat confirms my theory that the lower passage should have a plug in it. And if the photo is enlarged, even though the resolution is poor, you can clearly see the broken edge of what was a blanking cap that was at one time pressed into that passage to close it off.
All cleaned and being reinstalled. Yes that’s what came out of the bottom when we took the strainer off, so definitely going to sack that off.
I That makes a lot more sense now!! Thank you! So let me find something to blank this off with again, and then install the orifices as soon as I get them, and put the whole thing back together.
You should really remove the remains of the broken cap from the hole first, then measure the hole diameter and use a piece of suitably-sized round bar to make a new plug. When you install the new plug it should need to be lightly driven into place with a hammer.
Also, awfully sorry to be a bother, but do you think there might be a part number for the blanking plug?
Sorry just seen this. I’ll machine one out of round bar.
There might be a Part Number but it is not visible in the system. Your best bet is to make something to fit.
Another thought. After you install the plug use a centre punch to make a couple of dots at the interface between the plug and the valve body to ensure that it can’t move.
from what I can remember there should only be the one hole for the orifice I don't remember having to figure where the orifice went. I know that with out it you will have major high pressure. I had a customer that his filter housing blew apart from the pressure
While you have the control valve body apart I suggest to check closely for a small circular disc of metal with rough edges that will correspond to the missing piece of the plug. It must be somewhere and you don’t want it to get stuck somewhere that could cause chaos to the clutch oil flows. I would hazard a guess that it’s very likely still somewhere in either the valve body or the manifold that fits directly under it when it’s installed on top of the transmission.
Will do. I’ll machine it to interference fit and then do the centre punch on the rim.
Hopefully this is what’s causing the issue in this case as well, so fingers crossed plugging it sorts out the issue.
I will do. Thanks.
I have a d5h valve apart. It has a frost plug in one of the holes.
It says 3/8 on the plug.
Excellent confirmation of what should be in the valve body. Thank you.
Perfect!! Thank you!
Also interesting to note that the frost plug in the valve body shown in the photos posted by Mobiltech appears to be installed the opposite way up to the one that failed in your valve body. In your one the closed end that broke was on the top, in his it is at the bottom where even if the plug cracked like yours did the blank end of it could not possibly have fallen out.
Come to think of it, I’ve never actually seen a frost plug installed the way it was installed on my one, even on an engine block.
If you are going to manufacture a solid slug to block that port it makes no difference which way it is installed. It just struck me as strange that on your valve block the plug was installed what would be considered as the "wrong way round" compared to the normal way of installation.
So just a bit of an update: My local dealer just had one of the part numbers in stock, the 7G-9476 so I ordered that. It’s just been delivered, and it’s not an orifice. It’s a plug with a hole though it (I’m going to attach a photo) and when I Google the part number, both the orifice and this hole come up with the same part number. The lower hole (the one that should have a frost plug) upon closer inspection actually has this plug with a hole through it. So I’m not exactly sure what’s going on here.
The part that you bought would still be classed by Cat as an orifice, although it will be completely unlike the other one that you ordered which, when it arrives, will in simple terms be a plastic tube with a small hole in one end and a screen built into the other. Here are two photos. The one on the left is one of the photos posted by @Mobiltech . The one on the right is from your control valve taken from a post back on Page 2. I've rotated them so that they are both oriented the same way. The control valve for a D5H is a different Part Number to yours (8P3044 vs 3T5018). It may have the same basic valve body but it is shown in the parts drawing as having a cup (frost) plug Part Number 2A3746 (Ref #21 in the illustration) in the hole directly above the valve spool and no orifice in that area. This is the same as shown by @Mobiltech 's photo.
Searching through various Part Numbers of D6H transmission control valve that contain the 7G9476 Orifice Plug I came across a better illustration in a control valve used on a 3YG-prefix tractor. In Section G-G it clearly shows the Orifice Plug #30 in the same location as it is in your valve and what appears to me to be an open hole right next to it. How that works I'm sorry I haven't a clue.
Thank you for taking the time to look through this. So do you reckon I should just try to plug that hole and put a plastic orifice in the other one, or does that mean the pressure issues are being caused by something else?
We are getting crossed wires here..... The plastic orifice with the screen 9W-9830 and its associated O-Ring 5H-8853 (Refs 12 & 19) is installed in a totally different location. See the illustration below. It was on one of your earlier photos taken from the other side of the control valve, white in colour. The orifice plug 7G-9476 is shown as #34 towards the bottom centre of the illustration.
This is what the 9W-9830 orifice looks like inside. In round numbers the hole in the orifice (horizontal on the RH side of Section A-A) is only 1mm in diameter.
So does that mean that I leave the control valve as is? No frost plug?
I would say so. That diagram I posted earlier (Post #75 above) showing Section G-G with the "orifice-plug" in one hole and what appears to be an empty hole right next to it would suggest that is the correct arrangement. I would be interested to hear what others think. Have you got the transmission cooler off yet.? What did it look like inside.?
Okay. Yes I took the cooler off and sent it off to get cleaned. They put a flushing agent through it and whatnot, but nothing major came out, just a bit of sludge.
So this essentially means that the control valve didn’t really have any issues? So what else do you think I can check?
And I genuinely appreciate everyone’s time, patience and help with this.
Did the screened orifice show up yet.? Try blowing through the old one and the new one. Can you detect any difference.? Install the new orifice, reassemble the control valve and reinstall it would be the next step. Before you crank the engine up I suggest that you replace the transmission filter. Take note of the Part Number that you remove, it might not be the correct one. Also cut it open and look for material in the pleats of the filter media. Depending what you find in the filter, a look inside the priority valve and the steering/brake control valve might be the next step. The filter P/N should be 1R0741 along with two O-Rings 6D9157 and 2K4472.
So the screened orifice is not available locally, so we’ve ordered it in from America. That’s probably a few days out atm. I’ll open up the filter and have a look, and then steering control valve as well. Thanks
This VIDEO might help if you haven't done it before. Yes I know it's an engine oil filter but the principle remains the same. Squeezing the oil out of the media is key to being able to see what's lodged in it.
Hi guys I’m a bit late to the party here so sorry if I’m asking questions that you have answered earlier and I have missed them reading though everthing. When you tested pressures at the start did you test all the pressures and if so what were they? As I say I might have missed it but I can’t find them. Also is this a steering clutch/brake machine or diff steer? I think there might be a problem in the T&A doc that Nige gave you, it looks like it’s missing the pressures for power shift transmissions, I think it only has direct drive pressures. This a power shift machine you have I think? My machine is a D6H series 2 diff steer and this same T&A manual comes up for it. They also have one listed for it that says for diff steer machines and it lists the full test pressures for power shift transmissions. I think these would apply to all power shift machines not only the diff steer ones. Nige might be able to check and make sure I’m correct on my thinking here please? It lists pump pressure (on top of filter housing) as 495psi +-25psi high idle. Priority pressure at 420psi low idle +-20 So your pressure is still high but maybe new pump, cold oil, blocked filter could account for a bit too. I have attached a screen shot of the pressures I’m talking about. Anyway a have had a very long day so I hope I haven’t misread your thread and wasted everyone’s time with a very long post that isn’t relevant. Let me know if I have and I’ll try again after some sleep.
Yes it was the wrong one. I sent him the correct one later, along with the applicable SysOp & Specifications for a machine equipped with a powershift transmission. By the sounds of it every man & his dog had been in that transmission before the OP got turned loose on it.
Ah ok awesome I thought you would have rectified it already! I just wanted to make sure it wasn’t leading the poor guy down the wrong rabbit hole. Yeah sure sounds like the OP got left with the pineapple. So probably won’t be just a stuck valve or something easy your thinking? All the easy stuff checked? Other pressures? Cables adjusted correctly? Doing it in all gears? Anyway a very interesting thread to keep following. I hope he finds the issue!!
Back to the old adage - "believe nothing, trust no-one, check/measure everything at least once or preferably twice, and have all your findings & measurements cross-checked by someone else."
Just tested the pump pressure at the top of the filter housing, which I thought was oil cooler inlet pressure, and ran with it lol. So we’ve had the oil cooler out and cleaned, we’ll change the trans filter and then once everything is back together, test the pressures again. But like Nige said, trust nothing and no one, so I’ll just take everything apart bit by bit and hopefully find whatever gremlins are hiding in this thing! Thank you for your post mate!
Literally every man and his dog!
So apparently the cables were changed and adjusted, but I’m going to do that again as well! Here’s hoping!
Specifications - Page 16 onwards. Make sure you look at the parking brake linkage as well, it is right after the control cable settings.
So I’ve just opened up the plate on the end of the control valve. There’s 3no. 1.4mm shims, 1no. 0.9mm shim and 4no. 0.25mm shims. Does that seem largely normal, having so many shims in?
That sounds about right for shims.
I know the parts manual states "Use as Required", when it comes to the shims but I would assume the quantities quoted there would be the starting point for the Test & Adjust procedure. The quantities quoted are 1, 1, & 3 respectively. You have 3, 1, & 4. TBH for a starting point I would suggest to remove 2 of the 1.58mm shims and just leave 1 in there. Then leave the 0.9mm and 0.26mm shims as they are right now. In your OP you mentioned that the transmission pump had been changed. I wonder if at some point in the dim & distant past someone tried to put additional shims in the control valve to try to jack up pressures to compensate for a worn pump.? According to the chart in the T&A document removing 2 of the 1.58mm shims behind the load piston should drop P1 Initial Pressure by around 28psi. It shouldn't be hard to reinstall shims as necessary, but personally speaking I would prefer to start with pressures on the low side and increase them rather than start high and have to reduce them.
D 5h has 1 thick 1 medium and 2 thin shims.
They did seem a bit excessive tbh. I’ll reduce them to what you’re saying and then measure the pressures again once I’ve put everything back. Thanks!
Not a tad bit excessive?
Better than 8! I think haha
I’ll be opening up the priority valve tomorrow. If the priority valve pressure is set incorrectly, could that cause dragging brakes?
Bear this in mind. To set the Iniitial Pressure (with the control valve load piston plug removed) on P1 the specification is only 77+/-5 psi at Low Idle with everything warmed up to normal operating temperature. If the spec target is only 77psi and if according to the chart in the T&A adding/removing one thick shim will change the pressure by approximately 14.2 psi then two thick shims IMHO are going to change the pressure one heck of a lot.....!!!
Just take a look inside it first and, like the transmission control valve, report how many shims it has in it. According to the Parts Manual the starting point should be 1 thick, 1 medium, and 6 thin shims. Check the springs against Page 6 of the Specification document while you're in there, just to make sure they are the correct ones and have not been damaged..
You may have got the idea already but just to emphasise the point, you really need to check everything in the powertrain oil circuit looking for anything that out of whack. Missing parts, parts assembled in the wrong order, wrong/swapped springs in any of the control valves, etc, etc. That includes the inlet and outlet relief valves for the torque converter which I don’t believe we have mentioned up to this point.
I’ll be doing this today, and I’ll revert back soon on the number of shims.
Yes I saw the torque converter valves in the specifications doc you sent, and after I’m done with the priority valve, those are the next step. Oil cooler and control valve are going back onto the machine today, and steering valve and torque converter valves hopefully coming off.
Are you pulling all these valves off and adjusting the shims without already knowing the pressure in the circuit they are regulating? A pressure test of all the circuits would point you to exactly where you need to pull things apart wouldn’t it? I’m sure you have reasons for doing what your doing I’m just trying to understand how your getting there.
No. Based on the fact that so many people have had hands on this machine recently he’s inspecting them all to make sure they are a) assembled correctly and haven’t had spools reversed or springs swapped, etc and b) counting the number of shims in each one to compare with what’s listed in the parts manual which is the starting point for pressure testing. In the transmission control valve he found 2 additional thick shims over and above what should be in there to start pressure testing. That would increase P1 Initial Pressure by approximately 28psi and P1 full pressure by over 100psi which could potentially be dangerous. Those two shims in particular can always be reinstalled should test results indicate the need. I think I commented earlier that my particular preference for setting pressures is to start low and work up to specification, just to err on the side of caution.
Yep exactly what Nige said above
Yeah ok that is what I was expecting the reasoning to be, that is fair enough. The assembled incorrectly/missing parts theory is a very like cause of the problems. I would have gone about it by testing the pressures first to get a baseline and if things were way out of spec then adjusted accordingly or investigated area effected. Nige's method is probably a lot better then my method, just takes more time and may have to go back again to re-adjust them, but his is definitely safer for sure. It would absolutely have been what should have happened for the initial start up after the rebuild... but if you had done the rebuild you would probably have found all the extra shims too. I hope the damage hasn't been done already from the high pressures. Reading how other people go about troubleshooting is awesome, seeing different and better ways of doing this stuff is what is so great about the forum. So keep up the great work and I am sure you will find the cause, very interested in the outcome!! The fact it was driving for a bit and then stopping is very interesting
I may have read it wrong but I was under the impression that the reason it was stopping/being stopped was that the transmission (read powertrain) oil was overheating. For all I know the problem could be in the converter, but you have to start somewhere.
So the priority valve, apart from a fair bit of dirt, has 2 thick, 3 medium and 1 thin shim. The free length of the spring is 44.9mm as opposed to 45.7 spec. So I’ve removed one medium and one thin shim. Re-installing now.
Yeah just based off of the fact that I don’t know what was done to it initially, I’d rather not run it for too long and risk damaging something else. So the stopping was due to the transmission overheating. Well I hope it was, and not something to do with the converter like Nige said. Cheers man!
You should be worried about the dirt. It’s in that valve so by inference it’s going to be everywhere. Not good - extensive cleaning may be required. Spring sounds like it is very tired. The priority calve probably works harder than any of the others. Can you check with the dealer just in case they have one available.?
I’ve sent an enquiry, waiting to hear back from them.
That adds up to 6.15mm of shims. 2 x 1.6, 3 x 0.9, 1 x 0.25. The Parts Manual starting point is 1 thick, 1 medium, and 6 thin which in total adds up to 4mm. I would suggest to make whatever combination that you put back add up to 4mm.
Yes, I was thinking it was stopping driving and cooking the oil in the process while only going 150m. You had it correct though according to the OP, so my misunderstanding. I am very interested to hear what happens when it’s all back together after checking and adjustments. With dirt found in one valve, the valves on the torque convert will be interesting to see next.
Okay will do. I’ve got the torque converter outlet valve out as well, how many shims should that have as per spec? Thanks
It should have 5 medium (0.9mm) shims in it as a starting point.
Interesting! This only had 3 medium shims in. Additionally, the outer spring free length is 74.5mm against a spec of 75.7mm. The inner one was pretty much up to spec.
Remember that what the parts Manual quotes is only a starting point. Or maybe shims were robbed from there to put in somewhere else because the Part Numbers are the same for all three locations. Who knows.? If one spring is so far off spec I would suggest to try to get a pair of new springs if they are available.
Yes most likely, considering the fact that there’s so many extra ones everywhere else. I’ve enquired about replacements, so hopefully should be able to get them
Where is this screen located
Between the rear case and the pump suction. If you post a Serial Number I’ll find an illustration. You will have to remove a belly guard to get at it.
Serial # 4RC01914
4RC01914
Do i have to drain transmission oil to remove it ?
#15, right underneath the transmission pump. Access only from below AFAIK. You will have to drain the transmission oil before pulling the screen if you want to avoid a bath.
Thanks ! next ? Where is the plug located that you remove to see how much oil is in the torque converter ( no more than a gallon )
Bottom of the converter housing.
When I pulled the screen in mine the first time I didn’t drain it and was expecting the bath that Nige warned about! I hoped I would not loose the entire amount and I could just add the missing oil to keep trouble shooting….. I only lost a very small amount of oil, not sure if that is what is supposed to happen on this model but that is what happens on mine. It looks like there is an internal steel line that goes to the bottom of the case and the screen sits above the oil level??