We have an old 941 Track Loader that was working great till one day all the sudden 2F and 2R were gone... We have been using is as is, but would like to get 2nd back... Anyone have idea's of what this could be? Thanks
Clutch piston seals leaking. Later Bob
Take a look in the screen. If you have a burned up clutch it will be full of friction material.
Where is the screen I should be looking for located? Thanks
Bottom of the transmission - see illustration below, it's item 14. You will likely need to drop the belly guard to get at it. This screen is supposed to be removed and washed in diesel every time you change the transmission oil and filter.
I will check it next week sometime, currently in the middle of replacing the u/c and sprockets, its on wood blocks and dont want to crawl under there yet lol... Thanks
I suggest to keep any/all particles that you find in the screen, take a good photo of them and post them in this thread.
Hello Bob, I have the same issue with my 941, how do you replace the clutch piston seals for 2nd gear?
Hello, What was the final outcome of 2nd gear not working?
If only 2nd speed forward and reverse gears are affected and both first and third are fine, the speed clutches for second gear are the problem - it can be either the piston seals or the plates and disc's. As another stated check your filter and screen for debris. You will also need to pull pressures on the P1 and P2 ports and compare to spec. Keep in mind that there are two clutch packs engaged at any given time for any given gear. To replace the seal on the pistons, you will need to remove and disassemble the transmission - it is not a quick one two job.
An easy spot to poke a pressure gauge is into the plug on top of the trans filter lid, this will save any risk playing around in the top of the transmission, its hardly worth pressure testing but anything that helps understand things is a +, the next task to do is to drive the shovel up onto some timber baulks and try to get it up 1 foot higher than ground level as the transmission comes out easier from below, it can come out from the top its your call, on the thought it might be something wrong with the valve block the speed spool is a simple control 1 2 3 is all it does all the other valve controls work the same in any selected spool position, to remove the valve block is a fiddle so some rag stuffing comes in handy plus the valve is heavy, its best re-fitted in 2 half sections with great care taken. tctractors
The only pressure you will see at the pump housing is pump pressure. It will not indicate anything except for a bad transmission pump.
catfxr, I did say transmission filter lid just so you can get your facts correct, there is no point on the pump to hook up a gauge, anyhow with the pressure gauge hooked in at the spot I stated you can test all you need to test, with the engine running the pump pressure will show whatever its managing to put out, when the speed clutch packs are selected the pressure gauge will show the answer to any problem, I suggest you might like to try this simple test as it will save you looking a ****, I have been working on power shift 951-941's from the first build, so I think I should have at least some Idea on how to test them without wasting time, if an O ring was blown on the oil feed tubes it would not work in any speed, the O rings below the valve block have no chance to migrate, even if they did I would be sure the speed or direction clutch packs would still activate, the final word on the pressure test thing is try what I have said and stop reading to many CAT Service Books, if the piston seal or whatever is failed on a speed or direction clutch the oil pressure goes South. tctractors
We'll wait and see what he comes up with. I am sure you will be incorrect with your assumption. Not sure who you are or what you think you are, but if needed - re-read what I posted.
Catfxr, If I ever need any help to fix any CAT transmission I don't think I would send you a P.M. my assumption is I know my way around old bangers and I think I am my own biggest fan, but before you post any other things out of the Book, perhaps you need to enlarge on just how the oil pressure is going to top line when its pouring out of a piston seal as fast as the trans pump can send it, with a gauge hooked into the purge plug hole of the filter head just changing speed or direction will see the oil pressure drop off and build up, I see you are a Junior Member here with now 12 posts so well done, can I ask how long you have been fixing transmissions in CAT Iron so I can gauge your comment please. tctractors
32 years
Tony, what pressure would you expect to see if it's all good.
IH, it's not the pressure you see, it's the pressure you DON'T see. A gauge hooked up to the top cover of the oil filter housing as Tony has suggested will show pressure so long as the piston seals on whichever clutches are engaged for a particular speed are sealing correctly. As soon as you shift to a speed that uses the clutch that's dodgy (in the case of the 941 that's the subject of the OP that would be #4 clutch) the pressure on the gauge will drop like a stone - not necessarily to zero but probably quite close to it - and not recover until you shift to another speed because the oil is falling through the hole where the piston seal should be faster than the pump can keep up with it. A quick & dirty way of conclusively detecting if a transmission has a bad clutch piston seal without doing a full pressure test.
If all is good the pressure should hold 90% of high idle reading at low idle. The reading should be very close to speed clutch spec. Later Bob
Bobs script is bang on for the testing of the transmission pump on any CAT, the issue changes if the transmission is faulty in a section of the transmission, this test point on the filter head on D4/5/6/7/8/9 can be a simple and easy to get to location for a quick psi check also helped on the builds with engine mounted converters that have drive shafts to the planetary that spin in N and stop under a stall test, CAT service books often have people chasing around to pressure test systems, a classic point is the hydraulic system on the CAT Track Loading Shovels, there is most often a test point on the pressure line from the pump to the tank, this test point can be used to check all the pressure settings within the system, if you follow the service book you will be messing with hose fittings etc all day with no benefit just time lost, Nige, in his usual well scripted way has described the test effect in great form that might help some to understand this point. tctractors. p.s. I will post a few snaps of a valve block-pump job I did the other day on a D4D (same as 941/951) in shop talk (Caterpillar Sprocket Removal)
Thanks, Bob, Tony and Nige. Not one I've come up against, but you never know when this information will come in useful. Also, again I'm amazed how much knowledge and experience there is on here, and how generous most people are at sharing it. Catfxr, don't know a lot about you, but tuck your ego away and you might find even after 32 years there's new ways to skin, or fix, Cats. I've been operating, fixing and fabbing for longer than you and I'm still learning. Of course, that might mean I'm just thick.
OK.OK.OK, Catfxr might have come on a little strong, but hey ? haven't we all at some time ?, Its an excellent forum that has years & years of Knowledge from some very smart people who contribute their very valued comments and advice freely, I think he was only trying his best with his answer,may have upset a few, but what the hell, he is a new member. Ego time ? >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>.
Thanks! I will get pressure readings and remove and evaluate filter. The 941 was my fathers and is all original as he bought it new. He had the cylinders re packed and the machine repainted about 15 years ago before his passing. The serial number is 80H2745 which appears to have been built in 1971. I cleaned off the hour meter in the engine compartment and it reads 2026 hours. I was using the machine recently and running in second gear when it went soft. Reverse was soft also. It has the hand levers to pull back then apply brakes for turning. It seems odd to me that the clutch disks would be worn with 200 hours......but you never know. Lack of use is typically harder on machines than regular use. It is stored inside and I suspect either old seals of some sort or if it has the fibre plates they might give way....inspection of the filter shoud help clarify that. It will be a couple of weeks before I get pressures as the machine is at our farm. What is the port size and type so I can have the correct fitting on my hose......SAE o ring?? Or NPT?.
Correction... I indicated 200 hours instead of 2000 hours in part of my post, the machine has 2026 hours on the mechanical hour meter on the engine.
See my post #5 on Page 1. What you really want to be removing is the screen at the bottom right hand corner of the illustration. If a clutch is burned up what's left of the friction material from the clutch discs will be gathered around that screen. Post a photo of whatever you find. Tony will doubtless be along soon to correct me, but the plug on the filter housing is 9/16" - 18tpi from what I can see.
What seal is under the screen cover....gasket or o ring? The machine is remote so I want to take everything I will need with me. I would rather have to many parts than too few because of the remote area.
4H-2977 Gasket according to the Parts Book. It'll only be something simple and basically square. If you had some gasket paper with you most likely you could make one.
Garrie, again you are crack on with your post, perhaps I am a bit blunt at times so possibly need to offer the "Hand" to catfxr as we are all different and do things in our own way, in the U.K. there is still plenty of long time CAT men that have owned or run big No's of Tractor and Box (Pan) outfits, so you sharp find out how to test a Transmission without the mess about, I studied up the innards of D6 through D9 as a young skin and sharp copped on the best and fastest way to work out what bit had "calved down" I had a Slasher (Muck Shift Foreman) that could turn the air Blue and sack (Fire) drivers if it looked like rain never mind be late or slow in the saddle, so to keep my job I had to work like a whipped Donkey and be fast at it, I can recall asking for some new friction plates for the CCU's on 631's only to get a bollocking that lasted all week, so you might grasp that we had to fettle worn out parts a good bit, well anyhow the end result is Service Books are just an aid to a task with more simple and faster ways of sorting faults through working knowledge often being faster and better that words in a book. tctractors p.s. I am still my own biggest Fan
Well until TC shows up, if it takes an 11/16th wrench or possibly a 3/4 wrench (they make them in both sizes) the thread size would be as Nige says, 9/16" - 18tpi plug part number should be 9S4191 with a 3J1907 oring for a seal. To connect to JIC -04 Cat fitting would be a 2P1314. This gives a straight fitting with the STOR thread size of -06 and the JIC -04 male end.
And so you should be tc.
The filter housing could answer a few issues, firstly on the side near the bottom is a drain plug, this needs removing to check out the contents at the bottom of the pot, with the lid removed the filter is attached to it, you will see the oil ports to and from the filter (2 O-rings) the drain plug and the top purge plug are 3/4" socket size, I have a fancy box full of test port things (CAT standard Q'Coupler) that I use so the fitting detail is not something I need to recall but an O-ring seal at the bottom will come in handy, the pump pressure should be checked at low and high idle firstly from cold then after around 20 mins of running, if the pump is a knacker job you will see very fast a reduction in pressure, the scope of the gauge needs to be 600psi max on the clock if possible to give the sharpest reading, with the engine running at just below half speed with yourself sat in the seat and the bucket poked into the ground with 1 foot on any brake peddle or just both peddles depressed, pop the gear lever through its slots slowly and note the gauge findings, at full throttle on peddle steer shovels you need to stuff the bucket into a heap of muck with feet off the peddles when hot to stall things going forward, the stall test is not needed here though all you are aiming to do is verify system pressure through all speeds and direction. tctractors
Hello TCTractors, I look forward to the pictures of the valve block. Thanks to everyone for your help! My experience is minimal compared to this group but I will throw out something that has helped me to understand hydraulics a bit more. A couple rules of thumb.... Pumps produce Flow, not pressure (although they can produce flow up to the design specification) Pressure is the measure to resistance of flow Thanks everyone!
Mashley, I have a real fancy flow meter with a pressure loading control, but you would be a clever bugger to hook it into your transmission as the oil passages are all internal constructed being part of the gear case, so on this little item I would think you need to stick with looking for a bit of pressure, Hydraulics gets its name from the Greek word Hydross (all about a bit of water realy) the thing to remember is fluid does not compress, so a pint is a pint you cannot compress it to half a pint unless you have a leak?? tctractors
Most of this comes from a lifetime of experience on machinery. Wondering why, paying attention to what happens and remembering it. Later Bob