My cat #12 Motor grader clutch is stuck engaged . i parked it on a hill in gear for two years and now the clutch wont let go. 70D795 oil clutch. any ideas? thank you
I'm not positive on that model but it sounds like the friction disc is rusted to the flywheel or the pressure plate, or both. In most cases they will free up with a few lunges. Need a CAT guy to confirm any other option.
with an oil clutch will they rust?
It's my understanding that the "oil clutch" part is the engagement/disengagement method, like a hydraulic clutch system on a pickup or Jeep. It's possible that your "slave cylinder" that the pedal pushes has lost it's prime and is not disengaging the clutch. They can be bled just like bleeding hydraulic brakes. Look for a reservoir that would indicate oil level. It's also probable, as indicated by vetech63 that the clutch disc is rusted and stuck.
Thanks for the reply, but there is no slave cylinder. the linkage goes directly from the pedal to the engagement/disengagement part of the clutch. i took the linkage off the pedal and put a comealong on it to eliminate any adjustment issue. In other forums people indicated that in an oil clutch the discs would not rust together. but I'm not sure that's true or maybe i just misunderstood. For the dry clutch people talk about dragging it in gear with the clutch depressed to break it free. I might give that a go. does anyone know, should i use a low gear or high gear?
i personally would try high gear first- less likely to damage anything and try it gently at first
If you're dragging it, use high gear. If you start it in gear, and drive it over a bumpy field, use lower gear. I suppose an oil clutch could stick if it got condensation and sat for years, that would still be unusual though. You should be able to see a dry clutch through some sort of access plate, you might see an oil clutch, but you'll get a face full of oil first. knowing which should help a little.
By your own description, it's not a hydraulic clutch. It's mechanical. Pushing the pedal will not break it loose. As suggested, use high gear if you are going to try towing it to break it loose. Several manufacturers recommend "blocking" the clutch pedal in the disengaged position if parking the machine for any length of time.
Not sure if this is any help, but this is the diagram from the Cat 12 operators manual showing the clutch
I have a Cat 12 that i bought with a stuck clutch. I loaded it without clutch . Got it back to the shop and tried all kind of pushing with the pedal pushed down ,to no avail . we finally pulled the engine and had to wedge and pry the clutch disc of the flywheel. Hate to say it but thats your fix .
I would try backing off the internal adjustment and make a few attempts at starting out in high gear. Trying to get the clutch to slip if you will. If that doesn’t work it’s probably disassembly as Tugger states.
Take the inspection cover off the left side and check to see if the clutch release collar is moving. Might be rusted to splined shaft. Are you getting pedal movement?
Good stuff Terry!!!! Thanks for posting the manual pic!!!!
Yes when I looked through the inspection cover the pedal is moving the mechanism inside.
quart of kroil and a long spouted pump oil can` soak it down & let it sit couple days
^that is worth a try! I can see how it would ultimately rust up as the oil drained down.
It doesn't seem likely that an oil clutch would rust but if the oil had emulsified or was replaced by water due to setting for long periods of time it is at a higher risk of rusting. Great info Terry thanks
They DO rust. I know it seems unlikely but I have had to free up too many. I just did another 12 last year that had been sitting forever. I sprayed it down with diesel for 3 days, then lunged it a bit.
I was wondering if you can get some oil on there through that inspection plate on the splines and on everything else to help out. Thanks VTech. As with Dan, a mechanical grader is on my bucket list too.
I have seen a seized pilot bearing on an old truck grab the input shaft so hard, it was hard to pull the transmission away from the engine. They thought it was the disk stuck to the flywheel, but when you pushed the clutch, the disk, you could move the disk with a screw driver.
I have a 1957, 955C Traxcavator wet clutch settin' on the floor; the same concept though the parts are different. First off the clutch parts are heavy and spraying oil on them from the outside, sad to say, would be a lesson in futility. Though still worthy of a try ... gotta start somewhere AND please prove me wrong, I've been wrong before. The parts that would adhere to each other are the wear surfaces and contact points and a lot of those surfaces are under compression. If you did get them to move the surfaces will be extremely marred and decrease the life expectancy of the parts exponentially. I have read this style clutch is robust and my back would have to agree. The starter plate on one 955C had been removed and the Traxcavator had been run for some time. My conclusion; that is what destroyed the D315 engine but the clutch remains usable. The only scratches are the ones put on the center bushing by unauthorized personnel , me, pulling the engine so I could get it home. Terry140's pic talks about a sump, under the clutch, ... I am not 100% sure on your style but there may be an access port (great place far a magnet) to a screen. that screen may be plugged....Just a thought and also worthy of a look-see.
Maybe to clear up a couple of perceptions being given in a couple of posts here, an oil clutch means that there is oil in the bell housing and clutch case and it is slung thru all the clutch parts when the engine is turning. I've changed both type clutches in 112 and 12 graders that were manual shift direct drive transmissions. I will say the oil type clutches will rust up the operation linkages and the splines in the flywheel that the disks run in. On the 12 I saw the clutch material look like it was glued to the flywheel. The wet clutches that I remember working on were like a truck clutch in that there was a lock bolted into a spline and kept a ring from turning. Turning the ring one way or the other tightened or loosened the adjustment of the clutch. When you got it where you wanted it, you put the lock and bolt back in. The dry clutch I did in a 112 had fingers that had individual adjusting bolts. That clutch was slipping but the peddle was nearly impossible to push because of the rusted up linkages. I find the idea of starting a grader with a stuck clutch for the most part aggravating. The brakes were always a joke. Most of those fuel systems didn't shut down well and you had to cram the blade into the ground to stall the engine. That takes some time on the old knuckle busters and I hate the thought of the engine running, the transmission in gear and me inside the cab trying to get that blade dug into the ground enough to finally kill the motor. It wasn't hard to pull the motor on any of the direct drive graders I've worked on over the years. I think the labor for R&R plus the cleanup and clutch install was about twelve hours on each machine. Why take a chance on an accident that might change someone's life. It's not that expensive of a fix.
I would drain the oil from the clutch, fill the compartment full enough with diesel fuel to be well up on the clutch discs. With the linkage set up as far as possible toward the release side secure the clutch release in the release position. It can be pulled for and aft with the engine shutoff engaged, compression on, and will sometimes pop loose. Put the transmission in reverse when you pull it backwards. If only setting a couple years it should not be rusted that tight. Most I find setting for two years normally turn into two decades of sitting in actually. Oil clutches stick all the time when sitting. They are not covered with oil when not running and usually have lots of condensation in the housing because the oil was never changed, nor the water bled off in the last 25 years it was run. Good luck.
Thanks John C. and old-iron-habit for chiming in on the subject and clearing the air. I was just beyond my limits of knowledge on that clutch assem.. and down to possible options. old-iron-habit that is a great handle and I totally understand and so dose my wife ...
Running in essentially waste engine oil(Used from engine system) and sitting it can still corrupt. Follow instructions above and should come out of it, if not then will just have to come out.
It’s been a long time but here is an update on the stuck oil clutch for my number 12 cat motor grader. I tried all suggestions with no luck so I pulled the engine and found One of the clutch disk fused to the pressure plate. I apologize if I’m not using the correct term analogy. I will include a picture. I was hoping that maybe somebody could tell me where I can purchase new clutch parts. The tag on the greater says 70D795. thank you.
Now that is impressive!!
Coincidentally, I just pulled my No. 12 (80C) engine because the clutch would not disengage. Both of my friction plates were fused to the drive plate, flywheel, and pressure plate. I don't regret the clutch removal over the "drag it until it frees" option... I think that it's a better long term fix. Some have said that on oil clutches; the friction discs won't fuse to the plates... Not true!
Could you tell me where you bought your parts?
I purchased all new parts from my local Cat dealer; the gasket between the flywheel and transmission housings, throw-out bearing, what I call the pilot bearing and race, and the friction discs. I want to inspect the transmission brake, but first I have to remove the clutch actuating shaft. The shaft doesn't look like it will clear the frame but the service manual leads me to believe that it will. I used a scotch-brite pad on a variable speed drill with WD-40 to clean up the surfaces of the flywheel, drive disc, and the pressure plate. Be aware that I have not re-assembled my clutch yet... maybe next week. If you want part numbers then let me know.
Thank you. Part numbers would be great. My grader is a 70D795 would your part numbers apply?
In 57 years of owning, operating and fixing construction equipment of all kinds, including owning a sizeable number of Cats (including a Cat 12), I have never previously seen a Cat oil clutch stuck. Just goes to show, you learn something new every day, no matter how old you get. I can see where water or serious amounts of moisture has been in the oil though - and where you get moisture, you get corrosion. FWIW, I would have drained the clutch compartment and refilled it with a 50/50 mix of ATF and diesel. This is a mix that informed equipment restorers use to unstick rusted bores on engines. It works, it just needs a bit of time to soak in. For clutch parts, try John Parks at TractorParts.com (General Gear & Machine, Boise, ID.) John specialises in supplying a wide range of steering clutch plates and flywheel clutch plates. I did not see a listing for Cat 12 flywheel clutch plates on his site, but he would certainly be worth a call. FWIW, the Cat 12 oil clutch is generally an exceptionally long-lived clutch, it's not unusual to have them last for 20,000 hrs. https://www.tractorparts.com/
The following are the Cat part numbers for the clutch components that I am replacing. It is my understanding that the oil clutches in the 8T, 80C, 70D/71D, and 99E graders are the same, but I have confirmed my understanding. I do know that the oil clutch parts for the 80C are the same as the 71D series. You probably know that the 71D series is the 24v direct start grader while the 70D (yours) has the starting engine. 1B4113 - Throw-out bearing (Bower BCA1213) - Cat had the part but I chose to purchase one on eBay. 2H3517 - Pilot bearing 2H3525 - Pilot bearing race 2H3504 - (3) pilot bearing fold-over locks 6D2348 - (2) friction discs [5H48 is old part#] 5H0203 - Flywheel/transmission gasket I haven't removed and inspected the clutch brake yet so I don't have a number for it. RE: OzDozer's comment; On my grader, the friction discs did not rust to the flywheel, drive plate, or pressure plate. Instead, it appears that the friction disc material "melted" to the plates; Maybe because of excessive heat if the clutch wasn't getting oil or the clutch was slipping. There was oil in my clutch compartment when I pulled the engine, but I will confirm that the clutch is getting oil.
I should have proof read my previous post; "I have NOT confirmed my understanding" about the clutch similarities. One more thing; I had to pry the friction discs from the drive plate and pressure plate. It was like the discs were stuck to the plates with double-sided tape.
The photographs show the drive plates before cleaning and after cleaning along with the old and new friction discs.
I can't express in words how disappointed I am today. Engine is back in the grader but I still can't put the grader into gear while the engine is running. I was sure that it was the stuck friction discs but it's behaving the same as before the clutch rebuild. I replaced the friction discs, throw-out bearing, pilot bearing, and the clutch brake. While the clutch was apart I looked at the pressure plate and it looked in tact and all the fingers actuated. I adjusted the clutch and the actuating rod and checked it again. In addition be being disappointed I am at a loss on what the problem could be... Could there be something wrong in the transmission?
If the transmission won't go into gear, it means the transmission input shaft is still spinning, even though you have the clutch pedal depressed. Despite all your considerable amount of work, the clutch is obviously still not disengaging properly, or the clutch brake is not functioning as designed. If the entire clutch mechanism has been re-assembled correctly, the problem is in the clutch adjustment. The clutch brake needs to be working effectively to stop the input shaft from continuing to spin after the clutch is disengaged.
Did you use the correct adjustment procedure?
To adjust the clutch; First I adjusted the clutch pedal so there is about 0.010" clearance between the clutch fork and the throw-out bearing assembly. Secondly, I adjusted the three pressure plate levers to 0.125" clearance. I am going to remove the rectangular clutch inspection cover and actuate the clutch while the engine running. I'm not sure if it will be possible to see the clutch working or the transmission shaft spinning with the oil slinging.
Is this any help? The last 2 pages are out of order. Does your machine have the interlock and is it adjusted properly? Maybe its not letting the release fork travel far enough to release the clutch and apply the brake