1991 bronco II wont shift properly | Ford Explorer - Ford Ranger Forums - Serious Explorations

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1991 bronco II wont shift properly

boots6868

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harrisburg, pennsylvania
Year, Model & Trim Level
2003 explorer xlt
HELP!!!!
I will try to be brief but somehow I know there will not be short answer...lol
I recently swapped a 4.0 explorer into a 91 bronco II for a customer ( I don't have a fancy shop just like working on fords for good folks). He gave up on the old 2.9 and found a 75k mile 4.0 with all the harnesses entirely except for the dash wiring. I did my homework and found a wiring diagram on this forum that pointed out all the wiring on the drivers fender. long story short the engine runs beautifully. all systems go except one! I get a cel light and the bronco wont shift out of 1st gear. if I manualy select 2nd it will go there and I can run it out to about 50mph in second and the cel light will go out briefly throughout the rpm range which leads me to believe the cel is transmission related.
I went over my wiring tonight for the second time and cannot find missing wires.
this is the original transmission from the 2.9 I should add. and as far as I know it ran fine when the customer brought it to me.
why cant we just have it simple like the old c-4 trannys that shifted on vacuum? im hoping one of you tranny gurus can point me in the right direction on what it sounds like.
I used the 4.0 computer and relays along with the 4.0 engine harness. I retained the bronco headlight harness so I had to merge the two on drivers side fender as stated. I have all functions as normal. except for the shifting.
thanks for any help.
 
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janderson4010

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third boxcar, midnight train
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86 BII
i've wanted an auto in my 4.0 bII but I didn't want an a4ld, been looking for a c5 for a while and haven't been able to come up with one. Does the 4.0 standard have a different computer from the auto version? The wiring for the auto didn't look any more complicated than the one for the standard if I remember from when I was looking wiring diagrams over for my swap. anyway good luck.
 
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boots6868

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Im pretty sure the 4.0 the owner bought was out of an automatic. the swap itself was not hard at all. and the harness and computer were direct replacement. im sure if I was using the explorer tranny this would be plug and play. im headed down now to look at the wires for the 3rd time from the tranny to make sure everyone has home.
 
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janderson4010

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Im pretty sure the 4.0 the owner bought was out of an automatic. the swap itself was not hard at all. and the harness and computer were direct replacement. im sure if I was using the explorer tranny this would be plug and play. im headed down now to look at the wires for the 3rd time from the tranny to make sure everyone has home.

mine actually just had about 6 wires mainly for ignition to hook up. not to bad looking back. Runs good so far except the stock bII fuel pump is a pile. I'm gonna build a cell and get an explorer in tank pump for it.
 
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boots6868

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got her fixed!

after much looking at the wiring mess on the passenger fender, I looked at wiring diagrams for the 91 bronco ii with a4ld tranny paying close attention to wire colors from the transmission harness. I was getting a code 89 and 86 indicating 3-4 shift problem and converter lockup was not happening. what I found was on the 91 bronco ii the Tan/blue stripe wire was for 3-4 shift and the white wire was for converter. I then traced them to see where on the 94 explorer engine harness these went. Bingo runs and shifts perfectly I do however get a flickering check engine. after pulling codes I got 1-1 showing everything perfect. im guessing the expy computer doesn't like the A4ld tranny and something is getting the correct pressures because as im driving it while excelerating the light goes out until I let up on the throttle then it comes back again. Anyway pretty happy with the snap of the 4.0 on this bronco ii.
 
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janderson4010

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. Anyway pretty happy with the snap of the 4.0 on this bronco ii.

when I still had 31's on mine I could roast the tires all the way through first anyway, now i'm welded with 35's, and I didn't regear so it is pretty tall. The 4.0 is a great motivator for a bII
 
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