I have the PTO gear box cover off of the D8K. I lost both hydraulic pumps at the same time. However, after I removed both pumps the gears spun up by cranking the engine over with the starter??? How do I service the PTO with what weight of Oil when I put the cover on?? I can't find any information on this anywhere even at dealer or service manual??
Thanks Mitch

Lubrication for the PTO gears is part of the engine lubrication system. Not separately serviced although it wouldn't hurt to squirt some engine oil on the gears and bearings during assembly.
What was the cause of failure? Loss of splines???
If it is loss of splines, do not mix old and new without shortening pump shafts or they will quickly fail.
Describe situation so you can be advised.

Thank you for the reply. I had just knocked down a large tree with the blade high and dozer pretty high in the front. I backed off and headed to some other trees. Going with the decelerator at low rpm in high weeds. The blade hit a stump and I tried to put it reverse and it quit moving and the blade droped to the ground with engine still running. No movement or blade lift- nothing worked, so I shut the engine off. Resorted to my maintenance manual and concluded that the gear box or PTO shaft had broken. Removed both pumps and cover on the gear box. Both pump shafts and teeth in gear did not appear to be damaged. Took them to Caterpillar in Tulsa, Okla at Warren Cat. I had the shaft seals in both pumps replaced. Also I had them put new cartridges in the large and small end of the hydraulic pump. He said they both looked ok except for some chatter marks in the small section of the hydraulic pump. He said he didn't think it was a pump problem on either one. Both reservoirs transmission and hydraulic checked full before I started the tractor for the work. I had the work done anyway. He said he had never heard of two failures at the same time. The PTO gear box gears were ok, very little wear and shiny tooth engagement. He thinks I might got air in the system? Reservoir for the hydraulic fluid is also a question in my mind? How is it pressurized if it's left to sit for a few months? The tank has no vent and the cap is tight sealed. No filter indicator on my tank? It's a 77V 126xx serial number. No oil on the ground anywhere where it was parked or where I was working? If the tank developed a negative pressure would the pump get the fluid required? As I previously replied the gears turn when I crank the engine in throttle closed position? I haven't received the repair report yet on the pumps. I did pick up oil and necessary seals to reinstall the pump and all new filters. I didn't find any debre or metal in the magnetic filter or screen. It has snowed a ton and colder than you know what!! I'm 79 years old and can't work when it's like that!!  Any ideas, pinion gear, torque converter??
Thanks for any help Old Magnet. Mitch

Closed hydraulic reservoir is the norm. Provides air cushion to prevent hydraulic shock in system.
I take it you have not run unit since repairs. The PTO gears are driven by a shaft and timing gears at front of engine. Could be a problem there, maybe a sheared key. Probably enough friction to spin the gears with no load but will not handle pump loading.

On further checking the PTO drive shaft timing gear is integral to the shaft and driven by the large camshaft gear which is bolted to the smaller camshaft gear with a shrink fit and key to the camshaft.
If the engine still runs it's not likely the disconnect is there which only seems to leave the possibility of a broken PTO drive shaft.  Again could spin PTO gears with no load but not handle pumping load.

Hi Mitch, we had a D8K a few years back that didn't like to push limestone to steep in our quarry, as long as it was kept exactly on the full mark in the transmission it would starve of oil while pushing up, full of oil and a little less climb it would purr all day, awesome machine did everything our senior operator asked of it. I would say OM is on the task, cheers OM for all the advise you share thank you.

I am thinking your problem is in the valve bank, even if the drive shaft for the pumps broke there is no reason for the blade to drop to the ground. Your system is pilot controlled so there are some possibilities, unfortunately I no longer have a service manual for D8K. I do hope the fitter who fitted your new cartridges got their rotation correct, otherwise they won't pump oil, I did that once and learnt the hard way to check for correct rotation.

Wombat

As described, both pumps (transmission and hydraulic) ceased functioning. Both are driven from the PTO gear train. No blade control and tractor won't move. If you attempted to operate the blade without pump pressure I would expect it to drop.