JD400a Backhoe hydraulic blockage ??

[gotthebug]

Hi All,
I have trolled this forum for information however have been unable to find help for an issue my 1968 4ooA is currently having.
The other day while using the backhoe to move some soil the transmission oil filter seal blew out at great pressure, I first thought it may just be a faulty seal so purchased another along with a new filter & installed it however once started & the pump pressured up it just blew the seal rite out again. I have a feeling there is a blockage somewhere & the pressure is building up in the filter to the point of the seal letting go.
My issue is where do I start to look for the blockage as the only thing I know is that there is great pressure within the transmission filter canister but I dont know where the hydraulic fluid comes from to get to this point or which way it goes from here as the filter housing goes into the transmission block itself there are no lines or hoses from this point to indicate which way the fluid is going.
Unfortunately I do not have a manual & have been unable to locate one, even my JD dealer locally does not have one, may be just because there are not as many here in Australia, information seems to be far easier to find in the states & Canada than here.
Anyway if anyone can give me an idea as to where to start that would be great.
Thanks,
Mark

 

[Egon]

No help with manuals.

As it happened while working look at the control valves for anything amiss. Just quessing. Might also want to check if there is a plugged screen downstream of the filter. Does the transmision see pressure?

 

[Tx Jim]

1st thing I'd suggest is check trans pump & stand-by pressures which should be 165 psi & 2250 psi.

 

[gotthebug]

Hi Egon & Tx Jim, Thanks for the reply, as I dont have a manual I cannot seem to find any screens or mesh filters at all, I have been removing all sorts of bolts & plugs within the trans unit & have not come across one yet, I have also checked the control valves on the backhoe & even disconnected that section from the hydraulics system with no result. I also do not have access to a pressure gauge to test the hydraulic pressures within the trans, as much as I would love to be able to. Access to that sort of stuff is very limited here.