Im New To The Forum But Have Been A For D Man All My Life. Im Havinga Problem With My A.o.d. Tranny As It Will Not Shift Into Overdrive.1st Through 3rd Shifts Fine With No Slipping Or Hesitation.im Not Sure If It Is Related But The Cruise Control Also Stopped Functioning At Exactly The Same Time I Noticed The O.d. Not Engaging.i Have Been Advised That This Is A Simple Relay Gone Out To The Whole Tranny Is Gone Get A New One.any Information On This Subject Would Be Greatly Appreceiated.thanks For Your Time.
OD is engaged electronically. The computer gets a signal from the speed sensor, and determines from a variety of sensors when to engage overdrive. If OD won't engage, it could be a number of things from a faulty speed sensor (does the speedometer jump around?), to a bad TPS or hard fault in the computer (Is or has the CEL come on?). Also the OD solenoid could also go bad or stick. The good news is that the solenoids can be tested, and are not that expensive to replace. Just do some troubleshooting. Since the cruise control isn't working either, I'm leaning towards a bad speed sensor, especially since the cruise and OD stopped working at the same time. Does the ABS work either? On the cruise control, does the horn work, and is the airbag light on (if applicable)? If the horn does not work, the cruise control problem may be the clockspring inside the steering column and may not be related to the non-functional overdrive.
Check to see if there are any stored codes. A faulty MAF, TPS, or speed sensor can prevent OD from engaging. The computer can also set codes for too high or too low a resistance on the OD solenoid on several years. There may be codes even if the CEL is not on.
Thanks guys,sorry about the capitalization issue.Bear River I will attempt describe my problem a little better.The check engine light has been activated since I had a local shop swap in a new motor for me.It comes on and off but I had them check it with their computer and they said it was probably a short or bad sensor and as long as it is running o.k. that it would be fine to let it burn.Next the anti-lock light goes on and off as well and the horn is fully functional.The speedometer doesnt seem to jump around at all.I also swapped the tps and test drove it with no improvement.I also know that the stock comp has been replaced with a comp from a 1990 b-II and mine is a 1987 model,its been that way since I purchased it a couple of years ago.Thanks for your insight I will check the parts you suggested and let you know how it turns out.
I'm not sure about the way the ABS gets the signal, same with the ECU. I think a lot of Fords get the speed signal from the instrument cluster, since the instrument cluster also has the circuitry for speedo corrections. So the problem may be somewhere after the signal has been processed. You can get the ABS codes pulled and see what it is complaining about. Also pull the engine code, and see what it says. You should never leave a CEL on, mostly because if you have the light on for some minor thing, and then something major happens, you will not know about it right away because the light is always on. Its kinda like having a smoke detector that just randomly goes off, pretty soon it just looses all credibility.
You say you have an '87 PCM in an '88 truck that previously had a '90 PCM, is that correct? What year is the A4LD? '85 to '87 A4LD's only had one solenoid to electronically control the torque converter lockup clutch (TCC), and the 3-4 shift was vacuum controlled. '88+ A4LD's had two solenoids, one for the TCC and on to control the 3-4 shift. It's not unheard of to have an '87 A4LD in an '88 model year BII. Do you have an '87- A4LD (two wires for the EEc-IV connector at the transmission) or do you have an '88+ A4LD (three wires at the transmission)? When you refer to "OD" are you referring to 4th gear or the TCC? With and '87 PCM in an '88 (but who knows what year the transmission is from at this point), I wouldn't be surprised if you've never had 4th gear, and that you are referring to the TCC.
Common inputs for the EEC-IV transmission controls and the cruise control are Brake On/Off switch (BOO) and vehicle speed sensor (VSS, already been mentioned). On your BII, the VSS is in the tailshaft of the transfer case/transmission. The speedometer is cable driven, so the speedo on the dash may work fine, but that has no bearing on whether the electronic VSS is sending a signal to the computer. Did you pull codes from the computer as suggested?
Introducing the possibility that your BII is a collection of used parts from various years, it might be useful to take the time to be sure you know where everything comes from. There were quite a few differences in engine management between '87 and '88.
'87 Bronco II XLT 4x4 & '92 Explorer XLT 4x4 & '98 Chev Suburban K1500 SLT 4x4
I have a 89BII with no OD, all gears are good, no slipping, clean fluid. The TC will engage and disengage properly. I did hook up a pair of LED's to the TC and 3-4 solenoids control wires. What I found is after 35MPH the 3-4 solenoid will activate(LED will light up) But no shift will occure. The TC LED will light up when it engages and go out when its disengaged. Reading in about this dual solenoid tranny, I found that the 3-4 solenoid is a 2nd control over the hydrolic system. I just hope on my a4ld(just put it in) has that plugged screen or 3-4 solenoid.
I did find a easyer way to get at those pass side bellhousing bolts!! Pull off the pass tire and remove or bend back the innerfender, THAT MADE getting those bolts easy!
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