This started as an oil change when oil level was found to be low. 1967 D4D 78A7177. Pulled clutch drain plug--maybe one quart of oil. Hmmm, that ain't good! Removed oil pump screen to find the screen plate and bolts all but falling out, guess that's where the oil went. Have run this thing for maybe 20 hours since purchase not knowing it had a wet clutch until the repo service manual came, that is when the low oil was discovered. Yes, I know, the dip stick is like, right there by your foot, right? Hasn't been run since but to move it a couple times. The guy I bought it from impressed me to be the type to keep up on fluid levels and changes on his equipment, gave me a full set of filters and a full fuel tank at purchase. I am trying to convince myself the clutch had oil in it right up until I checked it as low, then the rest drained out while it sat...... Anyway, screen was full of very old looking gunk, searching around inside with my fingers caused a couple "things" to fall into the drain pan. Pulled the oil pump since it had to have been run with low to no oil. The drive gear had come loose on its shaft and wore its half moon key almost completely away, the clip was gone too, the driven gear, inside the pump had sheared its key, the key "top" grooved the backside of pump housing pretty good and buggered the shaft bushing. Odd thing, it turned over just fine and looked like it had never been run dry,nor was there signs something had been run through it. regardless the keys didn't get in the condition they were in for no reason. Returned to the drain pan and found what appears to be the end of a needle bearing outer race, just the roundish end "cap" that keeps the needles from coming out. Also a saucer shaped cup plug of maybe 1" diameter, the type that slips into a hole and gets popped with a hammer to flatten and expand it. Lastly, a bent up, flat wire 4-5" in length resembling the rail from a three piece oil ring off a piston. Looking in the service manual I am guessing the "needle bearing outer race" fragment and cup plug could have come from the clutch yoke? Can't tell from the book if the yoke has components similar what I am describing. The flat wire might be the retaining ring from the clutch hub bearing. Again speculation on my part. So, how difficult is it to pull the clutch on this thing? Can it be done without the fabricated lifting bracket and pole? If the dash is removed would a come along chained to the inspection cover holes work? The heck of it is, clutch worked just fine, never would have guessed there was a thing wrong in there.
The problem is the dash and hydraulic control tank sit right over the oil clutch housing. The tools or something similar are required to snake it out from under there. The suspect bearings in the clutch cover housing are sleeve type (bushing) bearings. Those clutches will take a lot of abuse but eating metallic parts is not one of them.
[The suspect bearings in the clutch cover housing are sleeve type (bushing) bearings. Those clutches will take a lot of abuse but eating metallic parts is not one of them.[/QUOTE] O.M. Found very little of what could be described as clutch material. The screen was about full of it but it would probably only fill a shot glass once to less than twice. From my description do you recognize any of the metal bits? After posting I got to thinking; if something above the pump gear fell into the gears that might have started the chain of events that resulted in the oil pump damage. Of the three things found, only the thin, flat wire looks as though it has been through a wringer (aka; gears). The cup plug is unscathed as is the thin, rounded half moon, Torrington bearing race looking bit are unscathed. The end breaking on this style bearing is fairly common, assuming that is what this is. I could, if broke down on the side of the road, repair this pump with just a couple half moon keys and a snap ring. It wouldn't be pretty but it would function.
I don't see any Torrington type needle bearings used in the oil clutch. Plug could come from anywhere. Ring segment could be a piece of broken retaining ring. Just because the scavenge pump goes round doesn't mean it is making pump volume and circulating pressure. So what do you want me to say? Will it keep working? yes it probably will. They seem to survive until you wear through the sintered bronze clutch facings or wear out the over-center roller mechanism. At least get it to where it will hold an oil level and keep oil in it.
Noooooo. I was only pointing out how little was wrong with the pump, heck it was still working in some fashion, not that I wasn't going to replace it. The wallowed keyways, loss of press on the drive gear, etc. require new parts. Minimally, gaskets and seals are in order too if the clutch cover is coming out. Since there is a small leak somewhere under the hydraulic tank that I have lacked the motivation to fix and I need to repair a hard line on a lift cylinder... If the tank and dash are removed, is the clutch cover able to be raised straight up out of the machine? The P.I.T.A. factor is rather large if the recommended method is the only game in town.
Just replace the pump group 2H2714, it was used on several applications and is still commonly available. Yes, with the tank and dash removed you should have a clear shot for removal. Probably with the choice to go out the top or bottom. PITA factor is part of working on any of this iron. If your going to be jockeying around the cover, install the new pump after the cover is in place so that the drive gear doesn't get bumped and you wind up bending the shaft.
Thanks O.M., if not for your advise a while back I'd not known to go after that screen. Paid $70 for Cat manual repo that is woefully short on info. Time to roll up the shirt sleeves. Probably recruit some extra hands too. Does the clutch oil/screen have a service interval like the engine oil/filter? Judging from how clogged this one was it would seem a schedual ought be followed.
Service cycle on oil and screen cleaning is every 1000 hours. You need to snag a copy of the "Lubrication and Maintenance Instructions" for the 78A1-up.