I have a 1980. Case 850 b trackloader w/ 4 in 1 bucket. Just bought it used. Very strange problem. After couple hrs of operation, when changing from rev to Frw the clutch does not engage. I move the lever back to rev. Clutch engauges. Do this couple times. Frw clutch engauges and I am back to work. Does this every so often. Trans oil full. Sometimes when this happens I notice the trans pressure gauge drops when i put lever in Ftw then sometimes shows pressure but still will not engauges Ftw clutches. Have put 20 hard hours on machine so far since I bought it. 4 of that today. Did this few times today. Any help would be great. Thanks.
Welcome to HEF Momacat1 :drinkup When it does the no drive thing in fwd, have you taken any notice if it attempts to drive while the FNR lever is in neutral? If you have not noticed, give it a go & let me know what happens.
no forward motion in netural or forward. wonder if there is a fluid additive availabl no forward movement in netural or forward when this starts happening. Is there a fluid additive to add to the trans oil. thought a bypass valve might be sticking open. not sure. i do not think there is any blockage from the suction of oil up to the charge pump because reverse allways works. Acts like when I put the FNR control stick in forward there is no pressure to force the forward drive clutche piston forward and put it in gear and no oil going to the torque converter to pressure up and move the tractor. feels like it is in netural. but remember this never ever happens in reverse. Rev allways works. not one problem. I have read where the suction line may be sucking flat but reverse allways works so I think that theory is busted. Any ideas would be great.
I realise that you would like this to be fixed, by simply putting some additive in the oil. Truth is your problem/s are likely more serious than that. If reverse is engaging every time it is selected, I don't think you have a oil supply problem. Does the machine have rippers fitted? Can you raise it off the ground to see if there is any drag happening in neutral? I'm suspecting it wants to go in rev when in neutral. But it's just a hunch..... There is a remote suction screen for the transmission. If something is going on inside it, this will usually show you something. You will need to check the oil control rings on the fwd/rev shaft, these live under the cover at the rear of the transmission at the PTO shaft.
case 850b stops moving forward when this starts happening, after I have backed up. back to forward no movement, netural-no movement, back to reverse and it moves backwards. sometimes you can put it in rev move the hi low levers to fast then move control to forward. it will feel like it goes into forward gear. then move the levers back to low speed and forward works. thinking it might be something in the control valve under the seat but not really sure. very strange. once the forward piston is in gear, spins the tracks when digging. we have doug a lot of dirt with this happening every so often. then unit works for a while. does this again, then works for a while. trans oil is very clear, still full. I have noticed when this happens sometimes the transmission pressure is low then when in rev back up high. is there a bypass valve that could cause this or is this more of a, pull the transmission out and dissemble for inspection kind of problem? Is there any use in pulling the control valve off and checking it out first? Should I pull the torque converter and check it out also? Want to get to the bottom of this problem. Is the low torque converter pressure a sign of sucking foam or air or bypass valve stuck open? strange that I have never noticed any problem with reverse. might be small pieces of clutch fiber or shavings not letting the forward piston move into place. Any thoughts? I was carrying dirt up a small hill. Hit both the turn brakes and it rolls back down the hill fine. Guessing that dissengauged the transmission. foot off the LR turn brakes. pulled right back up the hill forward. Unit has no rippers on it or anything else on back of unit.
The control valve for the 850B is pretty simple & is not likely to be the where the problem exists. I'm thinking broken oil control rings & possibly, damaged clutch pack/s. - still just a hunch....... You notice a lack of pressure sometimes - you need to isolate exactly when & where that is happening. When the machine is not driving in fwd, Is the driveshaft spinning? Fast? Slow? Not at all? AT operating temp, at an idle , select each gear, L & R low in Fwd, then put L into high, then R into high, then each one back into low. Also with both in low & then in high, shift from fwd to rev & back. Each time you make a selection - watch the transmission pressure gauge. It should have the same pressure at each selection & it should take the same amount of time for the gear to be engaged, with the same amount of 'jolt'. If one is slower or pressure is lower - there is leakage happening somewhere that needs attention.
finished digging a large tank. moved the unit back to my house/shop. went to move off the trailer. left track no movement at all. either direction. no high.low/frw/rev nothing. drove it up to my shop with the right track. pulled floorboards off. power washed unit. started it up to move back and clean mud off slab. now all drives work. independent, together, frw/rev. high slow everything. drive shaft spinning slows down when put into a gear. Will try pushing some dirt, get it warmed up and see if I can get it to fail. will see if the driveshaft stays moving when frw drive stops working and weather pressure gauge drops or not. right brake does not seem to be working now. Left brake is quick to work and dissengauge the transmission as it should. Will check the brake slave cylinder fluid level this afternoon. more info to follow.
Drop the oil & check the suction screen - if anything is going on inside the tranny, it usually tells the story.