Cat 931 Transmission Quit Transmitting! Help!

Hello everyone, I've enjoyed reading everyone's posts for the past year. Thanks for the info! I have recently purchased a 'new' 1974 Cat 931 track loader. It is in good condition with 2100 hours. Test drove very well.....did it all well. Undercarriage at about 75% with no leaks, etc. Got it trailered home, serviced it, greased it and eased into the work here at the farm. Eased me into the work as well as the controls are a bit different than my prior dozer experiences. Worked great! Moves dirt, brush, trash just great. For about 2 weeks of off and on use. I backed up to pivot into the dirt pile, hit the right brake / clutch and no pivot. Both tracks stop as in no clutch release. No left pivot either, just brakes. I shut her down after several tries in all gears without clutch release. I tried later, same result. Next day, worse. No movement fore or aft. I pushed and pulled it over to the shop area (with great difficulty!). I checked all fluids....within spec. Removed trans filter screen. Minimal shavings upon cleaning. I buttoned it back up loosely to check oil flow.....not much pressure, even at half throttle. Hmmmmm. Engine starts and revs freely. Tracks 'tic' into gear. No driveshaft movement to the bevel gear. So, what do you think? A bad torque converter would bog / strain/ overheat the engine?? Cat dealer says, " Bring it in, we'll fix 'er rite up @ $99 per hour.... open ended" Lots of problems with that scenario....$$$$ and transport, etc. Any help will be appreciated!! Mike in NW Arkansas

sounds like you have lost pump/system pressure. with low pressure you can not release the steering clutches to make a turn and are not engaging the clutches in the transmission to move the machine, what exactly is the pump presure that you said was not much ?

Hi, NWAMike, I have a 931b also, my book shows the torque converter oil coming in at the top of the tran., Also you have a screen and filter, did you ck each of them. The book has a trouble solving Ck list, first, low oil level, control linkage loos or adjustment not correct, failure of oil pump or pump drive, air leaks on inlet side of pump, leakage inside the transmission, adjustment of the modulating relieaf valve not correct or valve does not close, load piston not closing. Do you have the 3b foward, 1 reverse, transmission ??? good luck, wosama

kbeen said: sounds like you have lost pump/system pressure. with low pressure you can not release the steering clutches to make a turn and are not engaging the clutches in the transmission to move the machine, what exactly is the pump presure that you said was not much ? Click to expand... I don't have a pressure gauge ..... yet?? I just ran the engine with the filter screen cover loose. I expected a large quantity of oil exiting and at a pretty high pressure. Thanks for the help! Mike

wosama931b said: Hi, NWAMike, I have a 931b also, my book shows the torque converter oil coming in at the top of the tran., Also you have a screen and filter, did you ck each of them. The book has a trouble solving Ck list, first, low oil level, control linkage loos or adjustment not correct, failure of oil pump or pump drive, air leaks on inlet side of pump, leakage inside the transmission, adjustment of the modulating relieaf valve not correct or valve does not close, load piston not closing. Do you have the 3b foward, 1 reverse, transmission ??? good luck, wosama Click to expand... Yes, I have the powershift transmission. 3 forward, neutral at the top, 1 reverse on the left. It seems that oil pump / pressure failure is the track I need to follow. I will work my way through the problem flow chart here first until I get to something that requires the nuclear option......the Cat dealer.....with the transport nightmare and vast quantities of cash. Can I get some of that TARP $$? Thankfully, I found a complete service manual on Ebay for $ 78.00 vs. the $789.00 Cat wanted for the same set. Thanks for your help!! Mike

Hey NWAMike, The filter is on top rear, the screen on yours will have a cover plate on the bottom or end of the trany. Did you look at the drive shaft, if it is not broken, ck the flange that attaches to the trany, see if it has play, it is the one that connects to the drive shaft from transmission, you may need a small mirror and light to see if it has movement. I do not think you should leave the cover loose to ck pressure. wosama

wosama931b said: Hey NWAMike, The filter is on top rear, the screen on yours will have a cover plate on the bottom or end of the trany. Did you look at the drive shaft, if it is not broken, ck the flange that attaches to the trany, see if it has play, it is the one that connects to the drive shaft from transmission, you may need a small mirror and light to see if it has movement. I do not think you should leave the cover loose to ck pressure. wosama Click to expand... Will do. The filter on the upper / rear is the one I removed, cleaned and replaced. I will search out the screen tomorrow. My son is getting married today....it wouldn't do for me to be there with those permanent, black finger-nail beds that are surely to result. What am I looking for at the drive-shaft connection. Breakage, oil/air leaks?? Thanks for the continued help!! Mike

Hi, NWAMike, when you get back to looking, the screen cover in the book has 3 bolts, but i have 4 on mine, round plate. Have fun, wosama.

the cover on the filter screen that is on the upper right side rear of transmission is on the suction side of the trans. pump. on those little trans, the screen type filter is on suction side of pump instead of pressure side. only way to check pump pressure is by taking out the 1/8 inch pipe plug on top of the transmission valve body. there are 2-3 of the plugs so you have to make sure you get the one for pump pressure. your manual you have coming will tell you which one. good luck.

kbeen said: the cover on the filter screen that is on the upper right side rear of transmission is on the suction side of the trans. pump. on those little trans, the screen type filter is on suction side of pump instead of pressure side. only way to check pump pressure is by taking out the 1/8 inch pipe plug on top of the transmission valve body. there are 2-3 of the plugs so you have to make sure you get the one for pump pressure. your manual you have coming will tell you which one. good luck. Click to expand... Thanks alot for the help!! I'll keep you posted on what I find. Mike

This may sound stupid, but are you sure the parking brake is off? My 931C would act that way if the brake was set.

mx727 said: This may sound stupid, but are you sure the parking brake is off? My 931C would act that way if the brake was set. Click to expand... Yep, the brake is off. I wish that it was something as simple as that!! Thanks for any and all suggestions!! Mike

Hi, NWAMike, Hope you had a great time at your sons wedding, good to see couples get married. I wondered if you had a chance to Ck the drive shaft, a guy a couple weeks ago broke his. Also the flange that comes out of the transmission, that the drive staft connects to. Also ck the slave cylinder to make sure they are not loose, and ofcourse the lines that come out to the slave cylinders. Good luck, sam.

Had a 941B that lost the drive shaft connection. If you pull the belly cover you will see a flange on the tranny side and a flange on the engine side with what lloks like four hockey pucks between em, each puck has two bolts in each side of it. If you remove the pucks the engine side slides apart again with a male and female stub shaft mounted to the flywheel. If you break the male stub shaft you get the same symptoms as described. I lost one in the bottom of a river. You can weld em back together for a temporary fix to get the machine out of the boonies, but if the flanges dont run straight and perfectly aligned to each other you will beat the main bearings out of the engine, and front seal out of the tranny. Good Luck John

Sam, Excellent wedding! None of the relatives acted worse than expected... I haven't got any closer than 20 feet to the Cat. It is 'parked' in a slight depression. We have had rain off and on for the past few days. There is a moat of red clay mud an inch or two deep surrounding it. It is too slick to even attempt to pull it out with the Kubota. So.... a weather - related pause. I will definitely check the drive shaft connection as well as the slave cylinders. Thanks for your continued interest and help!! Mike

JD8875 said: Had a 941B that lost the drive shaft connection. If you pull the belly cover you will see a flange on the tranny side and a flange on the engine side with what lloks like four hockey pucks between em, each puck has two bolts in each side of it. If you remove the pucks the engine side slides apart again with a male and female stub shaft mounted to the flywheel. If you break the male stub shaft you get the same symptoms as described. I lost one in the bottom of a river. You can weld em back together for a temporary fix to get the machine out of the boonies, but if the flanges dont run straight and perfectly aligned to each other you will beat the main bearings out of the engine, and front seal out of the tranny. Good Luck John Click to expand... John, Thanks for the info. I will look into the driveshaft connectors as soon as I can get to the Cat. Thankfully, it is only 50 feet from the shop....Right in the low spot next to the big pile of rocky red dirt that was supposed to be the fill for said low spot....ironic. Thanks for your help!! Mike

Update!! Started the Cat this AM to raise the bucket and to get it warmed up because the "old-equipment expert mechanic" was on his way!! It started right up as usual, I put it in gear and viola' It moved forward and back ......but no turning. The mechanic arrived and started in. The shift linkages were all out of whack. They couldn't be adjusted correctly as something in the transmission wouldn't line up. It would start in neutral one time and then in 1st or reverse the next. Frustrating! We pulled the cover plate off the top of the transmission and discovered the problem. The oil pump mechanism as well as the entire guts of the trans rocked back and forth about a quarter inch. The high pressure line from the oil pump to the clutches was twisted out of its socket during the rocking maneuver, thus the lack of oil pressure to the turning clutches......and no turning. The Mechanic said there is 8 to 10 bolts that hold it all together inside and it looks like some are loose or broken off. The only way to know is to pull the transmission and start digging. So..... the next step is to talk to a shop the mechanic recommended to see if they can / will tackle a trans pull and repair. And to see what the budget will allow?? Thanks for all your input! I will keep you posted with any progress . Mike

mike what is your serial Number of the machine. from what you are saying in your last thread you have a early style transmission. the planetary gear train which i believe is what you are seeing moving back and forth is held in place by two 1/2 inch bolts that come in from each side of the case. they are external. they may have just came loose or backed out. if you have the serial # i can send you a picture of the two bolts.

kbeen said: mike what is your serial Number of the machine. from what you are saying in your last thread you have a early style transmission. the planetary gear train which i believe is what you are seeing moving back and forth is held in place by two 1/2 inch bolts that come in from each side of the case. they are external. they may have just came loose or backed out. if you have the serial # i can send you a picture of the two bolts. Click to expand... Serial # is 78 U 0737 External is too much to hope for! Thanks for your help! Mike

mike the bolts are item # 26 they are about half way down on the side of the transmission case. one bolt on each side.