Wiring diagram Ford 881 with S.O.S

KCTractors · Nov 18, 2007

I can not find a wiring diagram for a tractor with the Select-O-Speed. I know the safety switch is under the cover and there has got to be something more for the warning light in the transmission for the transmission control handle. One more question: I had to disengage the transmission from the drive -line to pull the tractor, when I removed the bracket to do this , there is something that came out from the case behind that bracket, it almost looks like a screw, what would that be? I just bought this tractor and is my first Ford with the SOS.

Anonymous-0 · Nov 18, 2007

KC,

I am interested in hearing this as I have just agquired a Ford 881 myself.

Allen

NWMO 901 SOS · Nov 18, 2007

Hey guys,

Thanks to John for providing these great wiring diagrams.

I am going to assume your tractors have the original set up. The start switch recieves power from the keyed ignition and provides a path to ground when pressed. The circuit is grounded to the top of the control valve assembly beneath the top plate between your legs. If original, it will only be grounded, and therefore start, with the transmission in Park. I am sure many have been shortcutted to bypass this safety when wires frayed, broke, etc.

The warning light you refer to is similar in that it receives power from the keyed iginition and is grounded to the frame. However, this circuit is grounded through a pressure switch which should open when the tractor is started and thus break the circuit. The pressure switch is refered to as the "lubrication sending unit". Because the wire to this sending unit runs along the side of the tractor, it has also often been broken and never repaired. It should go into the transmission through the inspection plate on the left hand side where the transmission disconnect is. As far as that goes, the thing you saw drop may have been an attempt to keep the location the wire should be in from leaking? Hard to say, but I can't imagine it to be anything to worry about.

Lastly, you may also note that the transmission top plate should include a vent to allow the transmission to breath. Mine had been capped and I believe that contributed to the transmission running much hotter than it otherwise should. Haven't noticed it much since venting properly.

HTH

Chris
wiring diagrams

Larry NCKS · Nov 20, 2007

[color=red:57dc0be8db]I just have a couple ammendments this time Chris :wink:

am going to assume your tractors have the original set up. The start switch recieves power from the keyed ignition and provides a path to ground when pressed. The circuit is grounded to the top of the control valve assembly beneath the top plate between your legs. If original, it will only be grounded, and therefore start, with the transmission in Park. I am sure many have been shortcutted to bypass this safety when wires frayed, broke, etc.

[/color:57dc0be8db]

[color=red:57dc0be8db][b:57dc0be8db]The start switch is not powered![/b:57dc0be8db] It simply grounds the four terminal solenoid, which receives power on the small I terminal from the key switch. [/color:57dc0be8db]

Lastly, you may also note that the transmission top plate should include a vent to allow the transmission to breath. Mine had been capped and I believe that contributed to the transmission running much hotter than it otherwise should. Haven't noticed it much since venting properly.

[color=red:57dc0be8db][b:57dc0be8db]The very early 01 series SOS did not have a vent.[/b:57dc0be8db]

KC, the illumination light in the shifter handle was simply tied into the unpowered side of the light switch or possibly the iginition switch. I've forgotten which, without going to look. As to what dropped, on the original wiring for the transmission idiot light, there was a molded rubber plug that protruded through the inspection cover under that strap. Over time they become brittle amd even break. Could that have been what dropped? [/color:57dc0be8db][color=red:57dc0be8db][/color:57dc0be8db][color=red:57dc0be8db][/color:57dc0be8db]

NWMO 901 SOS · Nov 20, 2007

Thanks Larry,

As always, I appreciate your teaching. I guess I need to consider the workings of the solenoid better and learn how they function. Did the unvented transmissions tend to run hot?? For what other reasons was the vent added?

Sounds like our warm weather will be departing and it will get cool for Thanksgiving. Have a good one,

Chris

john in la · Nov 20, 2007

Larry and Chris
From what I read on your post this wiring diagram should be correct.
Note the red wire for the trans waring light.

NWMO 901 SOS · Nov 20, 2007

Thanks John,

Your work is greatly appreciated and helpful to more people than you can imagine. Now, do you have a good link to help me better understand the functioning of a solenoid or a quick explaination :roll: ?

Chris

Larry NCKS · Nov 20, 2007

looks good, but I wonder if KC isn't asking about the illumination bulb in the shifter itself too.

KCTractors · Nov 21, 2007

One more question, is the starter relay, a 3 terminal or a 4 terminal. I will not be working on the wiring for awhile, I have to fix a BAD rear engine seal leak first. Thank-you to all you guys that responded, I appreciate that you took the time.

NWMO 901 SOS · Nov 21, 2007

KC,

Relay on my 1960 971 is 4 terminal.

Chris

john in la · Nov 21, 2007

All the X01 tractors have a 4 post relay.
While I do not have time right now check back tomarrow because I will be answering the question Chris had about how the differant relays worked.

NWMO 901 SOS · Nov 21, 2007

Thanks john,

Hate to see ya working on Thanksgiving, I'm just trying to get a better understanding, no hurry. I appreciate everyones help.

Chris

john in la · Nov 22, 2007

KC and Chris

So that it will help everyone I started a new post on how the relay works. Follow the link if you did not see it.
How a starter relay works

CORancher · Aug 12, 2015

Does anyone still have this wiring diagram for the Ford 881 SOS? I am looking for one to correctly convert mine to a 12V system. Thanks in advance!

(quoted from post at 21:56:01 11/18/07) Hey guys,

Thanks to John for providing these great wiring diagrams.

I am going to assume your tractors have the original set up. The start switch recieves power from the keyed ignition and provides a path to ground when pressed. The circuit is grounded to the top of the control valve assembly beneath the top plate between your legs. If original, it will only be grounded, and therefore start, with the transmission in Park. I am sure many have been shortcutted to bypass this safety when wires frayed, broke, etc.

The warning light you refer to is similar in that it receives power from the keyed iginition and is grounded to the frame. However, this circuit is grounded through a pressure switch which should open when the tractor is started and thus break the circuit. The pressure switch is refered to as the "lubrication sending unit". Because the wire to this sending unit runs along the side of the tractor, it has also often been broken and never repaired. It should go into the transmission through the inspection plate on the left hand side where the transmission disconnect is. As far as that goes, the thing you saw drop may have been an attempt to keep the location the wire should be in from leaking? Hard to say, but I can't imagine it to be anything to worry about.

Lastly, you may also note that the transmission top plate should include a vent to allow the transmission to breath. Mine had been capped and I believe that contributed to the transmission running much hotter than it otherwise should. Haven't noticed it much since venting properly.

HTH

Chris
wiring diagrams

NWMO 901 SOS · Aug 13, 2015

CORancher,

Here is a 3-wire conversion from John's library (wonderful resource, thanks again John). Note, it does not show the "low-pressure" illumination light for the SOS as I didn't find the exact diagram. I believe for the low-pressure warning light, you just pull "keyed" power from the terminal block to the lamp and the ground side runs to the low-pressure sending unit. With approx. 2psi or less, the sending unit provides a grounded circuit to illuminate the light. With approx. 2 psi plus, the circuit is opened and extinguishes the light. Mine is staying on more and more while I operate the tractor, I suppose my pump is getting a litte puny or some other challenge is arising. Just serviced the tranny oil last weekend and still notice it once the transmission gets to temp.

Chris

Sleuth · Jul 7, 2019

(quoted from post at 07:05:24 11/20/07) Larry and Chris
From what I read on your post this wiring diagram should be correct.
Note the red wire for the trans waring light.

Can you post a link to browse your library? I'm looking for anything specific to Ford 881 with SOS and right now I'm looking for wiring diagrams for the Ford 881 with 6V system.

Destroked 450 · Jul 7, 2019

You realize this thread is 4 years old!
A lot of guys that use classic likely won't see this.
Start a new thread asking for the info you need , you'll get a lot more responses.
I have a 881 diesel that's 12 volt, probably have the wiring diagram you need in my service manual but my brother has it at this time.

Destroked 450 · Jul 7, 2019

I suggest you also get yourself a service manual for you tractor.
I have this one. $23 on Amazon

Wiring diagram Ford 881 with S.O.S

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