Caterpillar 931 78U03789. I need to replace both sprockets and the way i see it i have 3 choices on how to accomplish this task. The first couple of steps are the same regardless. Step 1. Raise the machine body onto cribbing to remove track from ground. Step 2. Drain bevel gear oil and remove tracks. Having accomplished that I believe I have 3 different options and I was hoping some of you more experienced hands may have some good advice. Option #1. Call Cat mobile service truck to press new sprockets on and off with new seals. Option #2. Remove bevel gear housing with sprocket still installed, take to Cat shop and press on and off with new seals and then reinstall myself. Option #3. Remove bevel gear housing with sprocket still installed and use gear housing as a rotating work platform to grind off gear ring and weld replacement ring back on. And then of course regardless of method used, reinstall track and fill bevel housing with oil. Should I consider changing to a segmented sprocket so i do not have to remove it in the future? What are the potential issues with removing the sprocket while still installed on the housing? What should i be mindful of while housing is removed? What other consumables should I replace while I have it apart. Thanks in advance as always.
I haven't gone down the same road (but need to for my D4D) but I can suggest a few things: 1. Anything to do with a Cat shop will cost big $ 2. You don't mention pulling the sprocket yourself, probably because it takes a special hydraulic puller that you will have to find somewhere to rent one from... (I had to pull the clutch hubs on my D4 and ended up machining up a hollow shaft hydraulic cylinder 'cause I couldn't find anything in my area to rent/borrow and had no money anyway..) 3. Changing to a segmented sprocket is a good idea if you plan on running this girl long enough to need a new undercarriage in the future. 4. Welding a new sprocket ring on will take some patience to get the new ring running true with the centerline of the shaft. I am not sure of the recommended maximum runout when doing this but it may not be that bad. 5. Have you considered talking to a smaller HD mechanic outfit who has the hydraulic pulling tools -or knows where they can borrow/rent some- they can be a little less costly. 6. Depending on what you are planning on doing with this iron, will help dictate whether you want to just try to use a sprocket ring or pull the whole works down. Planning on using it to make money might suggest pulling the whole final apart and checking the bearings, gears, duo-cone seals, for cancer. If there are no indications of problems from the outside but the potential for future downtime is a big concern, I'd pull it apart and expect to spend some money on anything that looks tired. If its for a farm or a homestead lot where downtime doesn't mean as much, well, its your call. 7. Have you considered just cutting the sprocket ring off and replacing it without pulling anything? A guy could simply mark the old sprocket before cutting by rotating it and marking with a soapstone to get a concentric cut for the best chance of getting the new ring in place with minimum runout. If you wanted to get fancy tack on something to hold a side head grinder and grind each spoke to exactly the same length... Good luck and keep us posted on what you end up doing! Jon.
TnT - I presume from the Serial Number your relatively early model 931 has the shortened track frame? The earlier 931's had the track frame extending to the rear of the sprocket, which means the track frame is required to be removed to enable sprocket removal. The easiest method is to simply pop the sprocket off the sprocket shaft with a press, and press it back on. You can do this yourself with a bit of tooling. If you prefer not to get involved with tooling and doing the removal/replacement yourself, then hiring in someone with a press is the way to go. I would have to opine an independent mechanic with the pressing equipment will be cheaper than any Cat field service hire. Once the sprocket is off, the outer rim is torched off (reasonably accurately, to within 1-/8" - 3/16" diameter) and a new replacement sprocket rim is welded on. This is the cheapest option. The decision to install bolt-on sprockets is a curly one that produces more alternatives. 1. You can try and source a weld-on adaptor with bolt holes to take segments for your current sprocket. This means outlaying the cost of the adaptor plus the cost of welding the adaptor on. If you can do the welding yourself, that's a cost saving. 2. You can try and source good used bolt-on sprockets - or new ones. Either option may work out only a little more expensive than welding bolt-on adaptors onto your sprockets. It's only worthwhile installing bolt-on sprockets if you intend to keep the tractor for a considerable length of time, as the total cost of a bolt-on conversion would be substantial, and it will not add substantially to the value of the tractor if you sell it within a short time. There are no major issues with removing the sprocket from the sprocket shaft while the final drive stays on the tractor. Care in removal is necessary to prevent damage to splines. A lifting method such as a small crane is ideal - even an engine lifting crane will suffice. Replace all seals, check bearings for damaged races and rollers and check splines for damage (if they have ever been run loose). If the splines are damaged, then sprocket shaft removal and repair/replacement is necessary.
Late with the update but the route i went with was to purchase used sprockets from a D3-b and bought a 30 ton hydraulic gear puller and removed them my self. I used a steel choker through the sprocket holes attached to a chain hoist hung from the ROP frame to support the sprocket and an extension hose for the power pack as to allow me to avoid "shaking hands with danger" when the sprocket popped off. Installation was achieved by fabrication a bracket out of .5 inch steel plate attached to the new Sprocket and another welded to the body of the machine creating a space to place an alligator port-a-power head between the 2 and pressing the hub onto the shaft. Measurement was the only verification process as to depth of install as i had no way to track tonnage of pressure applied.