Hello - new to the forums. I have a 931 - 78U4301 - 4 in 1 bucket and a IH winch with immense pulling power. 3F - 1R trans. The previous owner said the original owner bought it as there first logging machine - and the business grew so fast the little 931 never saw much use. The engine has always started immediately, and the bucket has no problems with a 2 ton log, or wading through a wall of slash, or fixing a road on the steep slopes of the coastal mountains - its a good machine. I had the machine laid up for a month while the R lift cylinder was rebuilt at the CAT dealer. I re-installed the cylinder, and ran the machine for a few hours, turned it off, and when I went to restart it - nothing from the starter. The starter was getting power from the dash - so I figured a starter rebuild was in order. A 5 ton chain hoist to pick up the bucket and get the arms out of the way, and then drop the belly pan to get to the lower starter bolt. Lots of oily mud and fir needles in the belly pan - but no fresh oil - until I pulled the starter out - lost about 2-3 quarts of oil from the hole where the starter nose fits. The starter had a scant quarter cup of oil in it - and I am guessing that is why it wasnt working. I lost the service manual in a fire, and have not replaced it yet. I have a sneaking suspicion that there should not be oil inside the torque converter housing (bell housing?). The oil level in the engine did not drop, so I am guessing the oil has come from the transmission. What I need to know - is there a seal that I need to replace, and can it be replaced without to much work from underneath? I am hoping I can do this job with the machine parked out in the forest. If I cant, I am going to put the new starter on and drive down the logging road to a road where I can get an equiptment trailer to pick it up, so I can get the machine to a shop - and that sounds expensive. Any insight into repairs on the 931 would be a greatly appreciated. Thanks - Don Greydon
No expert on your machine but don't see an issue with oil in the converter area. The seal on the starter went bad but the converter has oil flowing thru it all the time.
Hi Don - The starter on your tractor is called a "wet" starter, it has an oil seal on the pinion end to prevent oil from the flywheel housing entering the starter. The seal has obviously leaked on your starter. You can generally purchase overhaul kits for starters, which kit would include the oil seal. However, less and less people are repairing starters today, because the price of new replacement starters makes repairing old starters uneconomic. The torque converter/flywheel housing has some level of transmission oil in it, but normally when the tractor is running, the transmission oil pump is sucking oil from the transmission sump and distributing it through the transmission and torque converter. The bigger Cats have a small scavenge pump in the bottom of the flywheel housing, which keeps the oil level from torque converter leakage, down to just a couple of quarts in the torque converter/flywheel housing. However, I don't think the 931 has a scavenge pump in the housing, the tractor simply relies on the transmission pump to keep the oil level in the housing down. I also have a 931B that I've been trying to get fully operational, and I have already replaced the starter on my tractor - and the oil level in the housing was just slightly over the starter opening, so I lost a little oil, too. However, I have not yet been able to get the transmission operational on my tractor, although I was advised it was driven to where it currently lies. I need to acquire a manual for my tractor as well, but they are extremely pricey. I do have a microfiche with the 931B manual on it, but a book is much easier to use, and you can take it to the tractor!
Remember many years ago when the local electrical shop branched out for doing automotive components to working on big stuff like 40 and 50 MT Delco starters. We had a problem with a starter leaking oil on some Cat machine after they had rebuilt the starter. I discovered the oil seal was there but obviously never replaced and also damaged. That's when I explained to them about "Wet Flywheel Housings"! Then years latter had the same problem on a 980G Cat. Starter full of oil! First thought was someone messed up the seal so had them redo the starter and again a few weeks latter same problem! I think what clued us into where the problem was is how dark the oil was while the transmission oil was nice and clean. That pointed in a different direction and the lightbulb came on! This machine had a factory prelube system on the engine that was driven by a small pump on the back end of the starter. By some simple wiring and a relay or two the starter would spin up but not power the solenoid while in Prelube function. Once a set pressure was reached the starter would stop and the solenoid would engage the starter to the flywheel and crank the motor up to start. Checking the system found that there was a check valve on the outlet of the pump and after sometime they would stop sealing good and the little gear pump on the back of starter was exposed to full lube oil pressure against the little oil seal for 8 to 10 hours a day!
Thank you AllDodge & OzDozer - I am going to bolt on the rebuilt starter and give it a try. I cant imagine trying to deal with an electronic device while working on a machine, so I ordered the manual. I put the 931 serial number in the Service Manual website - and, unlike the Caterpillar site, it finds my model. On my original post, I said the 931 had an IH winch - I think it is a JD 3315 winch - and it is invaluable cause much of my property is to steep to walk.
The Cat Publications web site only sells Parts and O&M Manuals, not Service Manuals. I have no idea why this is, before you ask. SMP produce manuals for Cat so they are genuine. Possibly because SMP already offer complete Service Manuals is the reason why Cat don't.?
The genuine, complete Cat Service manual for the 931 is massive, possibly over 1000 pages. It contains sections for every component of the tractor - engine, powertrain, hydraulics, and machine systems such as electrical. The sections are then split into two parts - systems operations/testing-adjusting/specifications - then disassembly and reassembly sections. A complete SM also includes the maintenance and operators manuals for the tractor.
Normally there shouldn't be oil near the starter mounting or bolts. I can verify that the starter is a real PIA to R&R and requires 2 people. A 931B has a gasket on the starter so I imagine a 931 does too. Easiest to take out from the bottom but requires the belly pan to be removed. Might want to use a 12 point bolt on the closest one to the frame. It's kind of a pain to get at to turn. I think I used a stubby wrench once and a socket with a long extension with maybe a universal joint another time. My machine has a Nippon Denso starter that some people have said to switch to a Delco but a shop that checked it when I had the engine rebuilt said the ND is actually a heavier duty starter. Unfortunately I've had to remove it a couple times since then. The last time was because it got corroded when I had to put a tarp over the machine to thaw the frozen tracks out so I could move it after being pulled out of a peat bog type soup. It's been good since that rebuild.
I installed 12 point bolts with close-fitting hardened washers under their heads, when I installed my new 931B starter, and modified a couple of ring spanners (straightened out) to suit the positions. The bottom bolt is certainly a trial. Never seen anything like that cramped starter fit. There's only one model of starter that fits the D3 and 931, because the solenoid has to be in one specific location, relative to the starter nose. You can get multiple starters to fit the 910 loader (same engine and drivetrain), because there's less restriction on the solenoid position with the 910, because the chassis rail isn't in the way on the loader. I took the old starter out the top, and put the new one back, via the top. They weigh 22kgs (nearly 50lbs), and it's not fun trying to hold it by yourself, and install the bolts at the same time. Starting the top bolt was the worst job, I ended up using a piece of fuel hose slipped over the head of the 12 point bolt, zip-tied it on, and twirled the hose to get the threads started. It was easy enough to pull the hose off once the bolt was started. I think having something to hold the starter up would be the go - such as a small engine crane. I couldn't run the engine to lift the bucket on my 931B - that was the biggest pain, the bucket was left sitting on a 200 litre (55 gallon) drum, and that was the bucket arm position I had to live and work with. This a Chinese aftermarket Nippon Denso copy, I bought it directly off the manager of the Chinese company making them, he said they manufacture 4000 starters a week! It even came with a Cat part number! LOL I think he might have slipped it out the back door when the big boss wasn't watching, and pocketed the payment himself. I asked him to ship it via DHL and it came via the most tortuous shipping route - he sent it in with some gate hardware in a sea container to a gate supplies company in Eastern Australia - then they redirected it to me! It took 7 weeks to reach me, and I thought he'd dudded me! - but he was honest enough to actually supply what I ordered! The starter quality looks just fine to my eyes, and it works great.
A helper holding the starter from the bottom is a huge help. I think I even used a little piece of wood to hold the starter up one time. I lucked out the last time the starter went in. Three mechanics in the military came out to my MX track to ride and were happy to put it in for me. I'm sure they've had their fair share of PIA jobs to do on military equipment. That Chinese starter looks pretty good but I think it's a little different from the original. Seem to recall 2 solenoids about the same size on the original. Maybe I can't see one behind the other in your pic. I can see why your starter comes out the top easier. I have the optional piston pump for the backhoe. There is a 1inch hyd. hose going straight back from the bottom of the pump and then the 2 inch inlet hose above it. I recently had to replace the 1in. pressure line. I had it made in 2 pieces because it has to go back to the firewall, curve around the back of the firewall then come down and go back to connect to line under the machine. Getting all the angles right for the fittings would have been difficult. Even with it in 2 pieces was a bit of a pain. Thankfully I had some help. It's a 4 wire hose so pretty stiff. The old hose did hold enough I could get the loader arms up. The old hose had a wear spot and I thought about replacing it way back when the engine was rebuilt but the shop said not to worry about it because it's a 4 wire hose. The hyd. shop I go to was pretty reasonable. I think the hoses were $138.00 or so but that may have only been for the longer one.
Agree original starter was a real PIA to remove on my D3, one bolt used a boxed end and was only able to move it one notch at a time, and that was by rotating the wrench each time. Replaced starter with a gear reduction model, was lighter and bolts easier to get to.
That there should win "Tool Trick of the Week"!
One time with the starter we took one of the small bolts out that holds the solenoid so we could move the solenoid just a little to have more clearance. Thinking about the hyd. hose I replaced I now think it was $238.00 not $138.00 but still much cheaper than going to Cat or the shop that did my engine.
I've used a piece of paper to jam a socket on a bolt before and thinking about it now, wonder if there is such a thing as magnetic sockets to hold bolts in tight spots?
Forget where I got the ones I have, could have been Sears years back or even a tool truck. Think the ones I have or at least used to have were more for say under 1/2 inch. A quick Google search finds many, one example: https://www.ebay.com/p/1355144050
Inserts, those would be handy.
A few spark plug sockets have a rubber insert to hold the spark plug for extraction - but the problem with the 931 starter bolts is the difficulty of keeping a socket straight on the bolt head, when there's major interference from the casting just back from the bolt hole. The fuel hose trick allowed for a flexible "angled" drive on the bolt. I forgot to mention, I trimmed the zip tie tail before I used the setup, so the tail of the zip tie didn't catch on anything.
This is what I have used in some tight places on starter bolts. Agree a 3/8 drive is a little small for the torque needed but that adapter is rated for 116 ft/lbs. so not that far off a 5/8 course bolt torque.