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1986 Bronco 2 4.0 swap


E.B.N.S

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Location
North Carolina
Vehicle Year
1986
Make / Model
Ford Bronco II
Transmission
Automatic
Hello there

I have a 86 bronco 2 auto trans with the 2.9. My uncle has a 4.0 engine that needs new head gaskets but overall is a good engine. I was wondering if someone already has a step by step and a part list of what I'm going to need to do this swap

Thank you
 
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rusty ol ranger

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1987
Make / Model
Ford
Engine Type
2.9 V6
Engine Size
177 CID
Transmission
Manual
2WD / 4WD
2WD
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Ive never done the swap so i dont know specfics but no one else has rolled in so ill share what i do know.

The motor, physically, will bolt in. The 2.9/4.0 use the same bellhousing and motormounts.

On a 1st gen BII i know theres some wireing that needs fooled with, i believe the gauge wiring is the biggest one.

Youll need a 4.0 ECM as well matched to whatever year the 4.0 is.

This is assuming its a pre 95 (EEC IV) 4.0 Later pushrod 4.0's and SOHC's will require more trickery with wiring.

Just my opinion if it were me and your 2.9 is running good id just keep running it rather then tearing into it...espicially if its your DD or only vehicle and you cant have it down for a time period.
 

Uncle Gump

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Just an FYI... I moved this to the engine swap forum.

This swap has been done many times. Specifics can be found in the Tech Library and by searching the forums.
 

franklin2

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I just swapped IN a 2.9 where a 2.8 resided. It's more wiring than I thought. I had to have both 84 and 86 wiring diagrams and had to study them carefully.

The 86 fuel injection harness had more body wiring in it than I thought. One of problems was the wiring for the transmission switch and the clutch switch. In 86 they did not have a speed sensor. So the computer uses these switches to switch some sort of idle strategy. I did not hook this up. We will see what happens because of it. But that is one thing the 4.0 ECM will need for this function, a speed sensor. Where will you mount this on the 86?

The fuel pump wiring is another spaghetti mess. It looks simple in the diagram, except when it leaves the fuel pump relay, the wiring leaves the fuel injection harness, and makes it's way through another harness to the enertia switch inside the cabin. Then it makes it's way back out, and finally down the frame rail on a pickup truck. This all has to be hunted down.

And you will have to hunt down a key-on ignition source for the computer system, and they use a different key-on source for the oxygen sensor heaters.
 

SenorNoob

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1988
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Engine Type
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Engine Size
4.0
Transmission
Manual
2WD / 4WD
4WD
Total Lift
1.5" Front + 4" Rear
Tire Size
245-70-R16
Early 4.0 speed sensor is the same as used on a late 2.9. I still have mine. Just left it on the end of the speedometer cable.

Studying wiring diagrams is a must. I spent a month working in my harness every day for 4-5 hours and I'm not clueless when it comes to wiring. There were several circuits that the wire color depends on which end of the circuit you are at.

I'm told it gets easier if you don't mind swapping the dash too... I didn't want to do that.
 

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