How are the hydraulics on the 880 Selectamatic supposed to work?

[hansh1212]

I just purchased a 1967 David Brown 880 Selectamatic and I have no idea how it is supposed to work. I have never driven let alone owned a tractor before so I am not sure if it is just me or the tractor that is causing me difficulties.

This particular tractor has a front-end loader with controls/levers that are positioned just to the right of the dashboard. The hydraulic hoses run to a “block” just to the left of the Selectamatic switch, close to the quadrant lever. Putting the selector switch to the “TCU/External” position does not switch the hydraulics to the 3pt hitch. The front-end loader is always active regardless of where the selector switch is positioned. The quadrant lever appears to do nothing regardless of where the selector switch is positioned.

To the left of the seat, many tractors have a 3-way selector lever to switch between the front-end loader and the hitch. Mine doesn’t have that.

Is there something I am missing in terms of how the different switches/levers, etc. need to be positioned?

 

[WIFarmKid]

The switch for DEPTH - HEIGHT - TCU/EXTERNAL is a "draft control" switch, it only controls the 3pt hitch. That switch can be in any position and not affect the loader. You'll notice a cable connecting to the 3rd point of the 3pt hitch (the top link), pushing and pulling on that cable can adjust the 3pt when selected to do so (draft control). When your implement pulls too hard it can lift it up a little, so the tractor isn't overworked, or something like that (I've never used draft control). One of the settings (HEIGHT, I think) is just full manual control, push the quadrant lever forward to lower the 3pt, pull the lever back to raise the 3pt (it is powered up, down is just by gravity).

I don't know what "many tractors" you speak of, but the larger David Brown models did have 2 hydraulic pumps. One pump runs the 3pt hitch, the other pump runs the "remotes" (loader controls, raise and lower an implement, etc.). Or by moving a lever (or button) you can put the pumps in parallel, with doubled hydraulic flow to the remotes (the loader moves faster), but the 3pt won't function (no oil supplied. It will still go down, but not up). Your tractor only has a single hydraulic pump, so it won't have that extra lever.

If your 3pt is stuck down, but the loader works, that means the hydraulic pump is working and the control valve for the 3pt is probably stuck/not working. The valve is inside the transmission, under the draft control switch.

If your 3pt is stuck all the way up, and it never goes down, you could be really lucky. There is a transport lock by the left side lift arm, on the rear of the transmission housing, and the 3pt could be locked in the transport position (all the way up).

 

[Joe Stewart]

Go to the following link and type in "loader" into the search box. You will get a ton of threads about loaders mounted on David Brown Tractors. Some of those threads should provide the answers to the questions you have. Here it the link:

David Brown Archive

 

[hansh1212]

Thanks so much for the response.
On my tractor, the pin to connect the sensor cable on the 3rd point of the 3pt hitch is broken so I will need to fix that. I am assuming that the 3-pt hitch would still work, no?
The "3-way selector lever on many other tractors" that I was referring to would be something like this (taken from an 880 manual):

I believe they were options on the tractors. Another version has a bunch of dials instead of a lever. While mine looks something like this without any lever or dial:


So what you are saying, then, is that there is no need to switch between the front-end loader and the 3 point hitch. They both should be "active" regardless of where any and all levers/switches are positioned. If the 3pt switch is not working, it is either because the lift latch is not released or a valve is stuck in the control-valve chest. Right?

 

[used red MN]

Hello Hans, welcome to YT. I see you are showing a diagram from a manual, so I assume you found the link to the manuals in the “Let’s fix this DB 885 post? The service or repair manual is the 4th from the bottom of then list.

 

[RGMartin]

The "block" is likely a "power beyond block". These came out well after the 880 was out of production, but DB really didn't change thier 3 point system much until the very end of production. As such the "PBB" is backward compatible, but not in any period owners manuals.

They work well and if the rest of the hydraulic system is OK, you should have loader function any time the 3 point isn't actively trying to do something.

The no lift condition is probably a stuck valve in the selectamatic valve body. if you are in "height" mode(center position), the broken cable is of no consequence.