Hello All, This post is just a follow up to work I have been doing on an excavator that I had purchased early this year. I was aware of what was needed upon purchase, learning the how to do it part is where this site came into play in a huge way. One side required a full rebuild of the final drive including a new gear hub, to which a whole series of posts and pics were previously posted. One of the planetaries had a bearing failure which tore everything up within that drive. The opposite side had an issue with hydraulic oil getting into the gear side of the final drive. The hydraulic pressure once built up on the gear side pushed out one of the toric (big O rings) and hence had a significant leak behind the sprocket through the floating duo metal seal. The culprit of the issue as suspected was the internal seal between the motor and gear housing. I had read postings / threads on this site that lead me to that being the likely issue, which was spot on for sure. I have a bunch of pics that I will post to illustrate what it looked like for my specific application. I learned allot in the first go round with the rebuild on the other final drive. Things like, leaving the the whole unit on the machine up till getting the large (15" spanner hub nut) broken free and off the motor housing head. Trying to hold the unit on the bench without a fixed housing or way to grab it was really hard the first go round. Keeping it on the machine allowed me to use a 4 to 1 multiplier and remove it without a whole lot of crazy effort. I manufactured a spanner tool to do the job, I'll post a pic of that tool as well. Once the nut was off, the unit was removed from the excavator and brought into my shop. Separated the gear hub after hanging it off of a motor crane to allow the head unit to drop out of it with the two offset bearings in it. One bearing stayed on the head with the other one coming out with the gear hub - it has too simply by design and fitment. The bearing on the head actually popped apart when trying to get it off, no issue as both were being replaced. I am guessing that a large press with the specific tooling could have been fabricated to avoid the bearing separating. Again, not an issue for me in this case. I removed the hydraulic motor head and internal piston, swash plate, brake piston and brake disk, then the thru shaft with the larger of the bearings attached. The seal was clearly damaged and had failed. It had parted at the face side and the spring and double seal was on the shaft and inward toward the motor allowing hydraulic oil directly into the gear side. No major bearing failure or the like was noted. There was a minor hitch in the larger bearing when spun by hand. replaced both bearings and the seal while in there, also installed new piston seals at the same time, despite no damage or failure noted of those. Just did not make sense to not do them while in this deep. Reassembled with new main hub bearings (2) and the duo seal between the gear side and motor. The freezer trick for the duo seals worked like a charm during the install after cleaning them with isopropyl alcohol. Assembled the gear housing onto the head and used large c clamps to pull onto the hub. A large press again could have been used with the right tooling up for it. The clamps worked like a charm and got the nut started and used both to get the gear housing close to where it needed to be. I had measured the nut recess internally as well as the external gap of the gear hub to the motor head for reference for the reassembly. I took allot of pics during the dis-assembly to illustrate positioning and orientation of motor head and all the internals as seemingly they would be critical. I put the unit back on the machine in order to torque the big spanner hub nut to the spec of 21nm rolling torque of the hub which in this case turned out to be 820 ft lbs = 1,112nm to the nut. Cat Spec says 1,245nm +/- 137nm. Once completed, the four set screws were coated with locktight and installed and torqued as noted in the spec. Then installed the gear sets, locktighting and torquing the set of 4 retaining screws on those gear mounting/retaining plates. Replaced all the planetary bearings as part of the process (total of 7 of those). Talk about just in time maintenance.. During inspection of the old bearings, one of them in the set of three planetaries had literally fallen apart in my hand once removed from the gear. The cage and the needles for about 1/3 of the circumference had failed. Seems I was very lucky to be catching this prior to it turning into a much more expensive repair - which was the case with the first side. I am hopeful to complete the work tonight with needing to fill the drive with new oil and then re pin the track together. See attached pictures. They are worth a thousand words for sure..
Toric O ring pushed out is what the previous picture is.
Good job and a nice photographic record of what you did. Kudos.
Thank You Nige, truly it is hats off to all of you on this site that are so gracious in sharing your time and knowledge. It is with your help I could get through this project.
I know you used torque multiplier but how did you know when you were at 820
Just thought I would say the Track is on backwards. tctractors
Looking to do my drive on pc270lc-8. Komatsu has tool list for drive were would we get them.or do I have to make them too.My problem would be removing bearings and nut and reinstalling them.Its a big drive , not sure yet what is wrong .I just found out last owner put grease in drive so we know it needs seals.
When I worked for a Komatsu dealer they had the engineering drawings for the tools and the dealer built them on site. As I recall the only items really needed was the fixture for holding the hub while removing and installing the big nut. This was on Dash 5 and Dash 6 machines. I don't know how different they would be on a Dash 7. You could likely contact the nearest dealer who might let you look over the tools and make measurements and photos. You could ask to rent of borrow them for you project. If you don't ask, the answer is always no.
A friend of mine built tool like the one he built hear which I could do. Removing bearing and reinstallation would be a challange. I might do that and give Komatus dealer a call.Bettter than spending 17500 on new drive that I don't have.
Komatsu and CAT both use Hi-Dash Track Drive heads on some Excavators, the gears needs setting / timing in position on assembly, I just thought I would say. tctractors
I have the shop manual disassemble and assemble it doesn't say anything about setting and timing.
The timing issue was only on certain machines. The PC400-3 used a differential reduction that required timing. The High Dash units I've worked on generally were so damaged that they were not economically feasible to repair them. I don't recall seeing the timing numbers on the gears of those units but that doesn't mean they weren't there.