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Discussion Forum
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770 Hyd system

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Brian (NE)

09-13-2002 09:48:37




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What is the easy way to inspect the pump on a 770?
It develpoed a major leak. Initially seemed to be under pressure, them just ran out (according to my father-in-law). What are likely problems?
How do you do a quick inspection? Can you disconnect the pump so we can use the tractor until we have time to fix it?
While we're in there, is there a way to take a pressure line out of the system to run two additional valves for the loader? That way we could eliminate the PTO pump.

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Nick

09-13-2002 20:06:39




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 Re: 770 Hyd system in reply to Brian (NE), 09-13-2002 09:48:37  
You can add a value or take hydraulic power from the Oliver hydraulic. I have seen a number of steering units operated off this hydraulic system. A vlave for a loader can be operated also.
On the left side of the unit there is a pipe plug in front of the front hose port. Remove this plug and insert a smaller plug inside(about two inches)form the one you removed. This outer port, or the one around the corner directly in front of it is your pressure hose going to your external valves. From the valves, the return line must go the the port directly in front of the oil filter base.
If you want to run a loader you usually need to add reservoir capacity as loader cylinders are quite large.

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Ed

09-13-2002 19:04:18




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 Re: 770 Hyd system in reply to Brian (NE), 09-13-2002 09:48:37  
Brian

We just experienced a similar problem with our 1958 770. The hydraulic pump was leaking oil into the transmission. As Bob has mentioned the PTO shaft must be pulled out of the transmission prior to removeing the pump. Our pump had a cracked center casting. Luckily I was able to buy a replacement from a tractor wrecker, but new castings are available. The IT service manual for the 770 has a good description of the hydrualic system. Looking at the drawing I don't see an easy way to tap into the pressure circuit to add more control valves.

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Bob

09-13-2002 17:32:53




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 Re: 770 Hyd system in reply to Brian (NE), 09-13-2002 09:48:37  
The hydraulic pump cannot be unhooked without removing the power shaft that runs from the pto thru the pump and into the flywheel. The pump is easily removed after you take out power shaft. Then you unbolt the housing from the top of the trans., remove the gear shift lever, don't drop the springs from the shifter. It is easier if you take the seat assembly off, but it is not nessacary. Then unbolt the pump for repair, usely the mounting end of the pump needs to be milled or surface ground. If you do this remember to remove the same thickness from the end of the pump gear shaft on the same end of the gears.
Replace the seals, two on each side, the outside seal faces out and the inside seal faces in.
Check the bottom of the hydraulis housing for crackes.

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Brian (NE)

09-16-2002 09:51:35




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 Re: Re: 770 Hyd system in reply to Bob, 09-13-2002 17:32:53  
Thanks guys, Sounds like I should buy a book, but I'll probably just go for it. I learn more that way.

Nick, You're saying I'll pull out a 1/2" plug (for example) and put in a 3/8" plug deeper in the same hole?

Brian



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