Hello, I'm new to the forums. I have a 1975 D6C Caterpillar Dozer with the following information: MODEL No. D6C SERIAL No. 47J 4474 ARRANGE No. 3P1777 ENGINE 3306 49V 7370 2P6795 I wasn't operating it when it locked up and I'm not sure my brother-in-law is telling me everything. The engine runs fine and shows 300 PSI at the Transmission Oil Pump. The blade operates normally. I disconnected the Universal Joint and the Torque Converter turns freely but the transmission will not turn at all. I've been told that it shouldn't turn even in neutral but I'm not sure. I bought a Torque Converter ($1,200.00) and was going to change it but now I'm not sure it's the problem. Where should I start to diagnose the problem? Any help here would be greatly appreciated. I really can't afford to have a mechanic come out into the middle of nowhere to fix it. Thanks! Brett
Your transmission input flange should turn when the motor is off. Bob
That's very good to know. The dozer is sitting on level ground and the input won't turn. Is there a "likely" cause? Thanks so much for your response. ~Brett~
If the transmission is locked up it will have to come out to be fixed, there are a bunch of parts inside that can break locking it up. Bob
I was afraid you'd say that... ~Brett~
If you decide to fix this one hire someone who has worked on them or try to find a rebuilt one with a warranty. Good luck Bob
Ok. Another quick question. Should the Torque Converter spin with the engine running and the input flange disconnected? Thanks, Brett
It should . Do you have a winch on that tractor? If you do they can lock up and since it drives off the transmission main shaft it will appear the transmission is locked up. Bob
Bob, No, it does not have a winch. Thanks, Brett
Just for fun I would pull the magnetic filter to see what might be in there. I could not find a picture on SIS of where it's located but believe it is under floor boards about where your left foot would rest while sitting in the seat. A square cover about 4 inches square with 4 3/5 bolts or nuts holding it on. Don't think you should loose much if any oil taking it out.
I'll take a look at that tomorrow kshansen . What should it look like? Thanks, Brett
Missed an illustration. See #18 below. Post above shows what it's like inside.
Nige, Thanks for the illustration. If it's stopped up would that lock the transmission? You guys are awesome! Brett
If you have 300 # on transmission pump screen is not plugged . no it won't lock transmission. Bob
Like Nige said the trans has to come out probably a planetary has come apart when that happens it gets real messy inside.Iron Peddlers has rebuilt exchange ones I believe they have a place in London KY i don't know if that is near you 704-389-8591 is there main office. Or get a experienced mechanic to fix yours. either way you are going to spend some big money
Found a picture that might help you find the magnetic strainer: My thoughts on checking it were not to indicate that cleaning it would make problem go away just to give you an idea of the damage you could expect to find when removing the transmission. Also note that if you either rebuild this transmission or opt to go the route of an exchange unit cleaning everything that the oil comes in contact with will need to be cleaned. This includes lines and hoses, pump, cooler and so on. In my opinion when it comes to the cooler I would lean very heavy in the direction of replacing it, either with new or reman unit, there are just too many places inside them for things to get caught and then pop out at the worst time.
Something like this on the magnets would be the best indicator of a mechanical hernia. This is not a transmission screen BTW but the concept is the same. What is stuck to the magnets is the indicator.
Where did you find THAT Porcupine Nige? Have seen some close to that but never quite that rough!!
My library of photos is full off examples like that...!! I usually only get the call after things go bang in a big way.
Sorry for not getting back to you guys sooner. My brother had cancer surgery and I had sympathy surgery. The dozer is still sitting out in the field. *Pictured before it locked up.
With the Transmission in N the drive shaft should spin free, when you select a gear the shaft should stop, if you remove the drive shaft U/J's from the flanges the torque shaft can shoot out if the engine is run due to the oil feed to the shaft, if the flange on the transmission cannot be turned with a bar the transmission has an internal fault and need a strip down, the 47J is a Glasgow built Tractor, the 2 spools in the control block are adjustable and need to be set in the correct position, it might be worth you checking that you are getting a Neutral position on the speed control, so you need to feel 3 detent positions on the speed sector. tctractors.
There was a guy out there looking at it last time I was there. He disconnected the drive shaft from the U/J's and started it up. nothing happened. The Torque Converter spins freely with that disconnected. Is that normal? Thanks again for all of you guys help and knowledge. *Can I get an admin. to remove that third picture I posted above. I got a little trigger happy when I was uploading them.
Well it would seem you were Lucky as the shaft from the Torque can and will fly out dumping oil fast if the engine is run up, again if the Transmission shaft is locked up it sounds like a gear has had enough on the main carrier. tctractors
It sounds like the torque converter is bad as it does nothing when the motor is running. I can't imagine what would cause the TC and transmission to go out at the same time. Thanks, Brett
I think you're getting confused. In post #23 above you said the torque converter output flange spun freely wihen the engine was started with the drive shaft disconnected. This is normal and indicates that the converter is rotating. What Tony was pointing out is that you were extremely lucky while performing that test that the converter output flange didn't fall out. It would not have been surprising if it did, but the fact that it didn't does not necessarily indicate that you have problems in the converter. Next step is to get into the magnetic screen (see KSH's posts & pisctures on Page 1) and see what debris is in there.
Nige, I'm sorry I didn't explain it well. The converter didn't do anything when we started the dozer (with the flange disconnected). It does spin freely by hand though. Thanks Again
In that case you may be looking at a loss of oil pressure. The same pump supplies the converter and the transmission. Suggestions as before, get into the magnetic screen and see what debris is there before proceeding further.
So now you are saying that with the engine running and the U joint disconnected the converter does not spin. does your blade hydraulics work
Dave, sorry for being slow to answer. I worked all weekend. The answer to your question is yes. With the engine running the blade hydraulics work. I think it shows 350 PSI on the front pressure gauge.
If the torque converter don't spin with engine running then you have a problem in the converter and you should be able to spin transmission input shaft with it not running it will have some resistance but should spin by hand. Like Nidge said you need to check to see if you have oil flow through torque Converter converter inlet and outlet pressure should be checked, But a quick test would be to unscrew the temp gauge and see if oil pumps out when running but be ready to shut it off a lot of oil should flow out.
Thanks Dave! I disconnected the temp gauge to do this test but the batteries were flat so we couldn't start it. We pulled the batteries and have them on the charger now. I noticed that the hydraulic pressure gauge was stuck at 150 PSI. My brother ordered a new one. The last time we started it the front blade would go up and down. Is the hydraulic supply going to the torque converter the same as the blade or are they separate? Thanks again for all your guy's help!
Simple answer to that is no! The hydraulic system that lifts the blade is separate from the hydraulic system that works the converter and transmission. Separate oil supplies on pumps.
The blade hyd. pump drives off of the torque converter that is why I asked if you had blade hyd. I have seen the gear drives come apart before if that happens the trans pump would not drive either
I have somewhat limited experience on D6C's, only had two where I worked and they moved from plant to plant around the state so I might not be the best on this question. Just to be sure I was not giving bad information I checked on SIS and found this statement regarding the hyd. pump: When the hydraulic control is installed on a D6 Tractor, the hydraulic pump is mounted on the left front side of the engine flywheel housing and is driven by the drive gear for the hydraulic pump. May be a little nitpicking but just felt saying the pump was driven off the converter was not accurate. I do recall that the same gear train in the flywheel housing does drive the transmission pump and maybe even the back side of the same gear as the hyd. pump.
I know it is driven by the pump drive in the torque divider. I was just checking to see if he had a problem in the gear train of the housing thus messing up the converter. there is also a planetary in front of the converter. HE did not seem to knowledgeable on this machine so I did not want to complicate it for him
Pump drive, both for transmission and blade are driven from it's own gear train driven from a crankshaft gear ahead of the flywheel .
I kind of thought that was how Cat did that, very much like the 966C Loaders. I know other companies like Hough, Trojan and Michigan drove the pumps off the back side of the converters. Some of those had a fiber spline coupling on the flywheel that would fail and everything would stop working!