90+ A4LD in an 87 Mustang - Overdrive?

[Ourobos]

This is my first post, hi guys. I was refered to you by Silverfox at www.clickclickracing.com . Here is my problem. I have a 2.3 Mustang that had a bad tranny that I bought. I got another A4LD and installed it this week. Problem is now I have no overdrive. I have the TV set tight for now, but nothing. Apparently the 87-89 A4LD had a different way to engage overdrive, and the 90-93 had something else. One thing, on this tranny, there is a small two prong connector on the front driver's side that connects to something in the engine bay.I think this is the connector that overdrive uses, as I couldn't hook it up, mine was different. I have been told to swap a 90+ ECU and harness in and it should work.. I can do that buy it'll be a pain.. Someone told me to put the valve body from my original A4LD in and it will work properly.. THIS is what I am wondering is true or not? Any help is appreciated.

Thanks
Brandon

 

[MrShorty]

I don't know for sure if it's the same in the car A4LD's, but in RBV's, '85 to '87 A4LD's had a two prong connector for a single solenoid that controlled the torque converter lockup clutch. 3-4 shift was vacuum controlled. '88+ A4LD's used a three prong connector and two solenoids: one for TCC lockup and one to control 3-4 shift. If you haven't plugged that connector in, then that is why you don't have overdrive.

I've been led to believe that the valve bodies are essentially interchangeable. You may have to do something with the case connector, too.

What year is your Mustang, and what year is the A4LD that you swapped in?

 

[Ourobos]

My mustang is an 87, and the transmission I put in it is from a 91. My old transmission DID have the 2-prong connector, and this has the 3-prong, just as you described. I was told there was a way to wire this one in for the OD to work, what are your thoughts, here is the information I was given :

"No the mustang has electornic lockup, hydrolic OD, the TC with the dual selinoid has 3-4 kickdown in addition to electronic lockup.

If you wanna get your mustang to lock up you gotta wire in the VSS to the ECU which I am pretty sure you did not do since most swaps ignore this. its pins 3 and 6 on the harness.

The harness comes into the car so you can splice the VSS from there, rather then having to wire it under the car. theres a small harness with about 4-6 wires in it that runs under the drivers seat, and along the area directly next the door sill under the carpet. the main body harness also runs there, you want the smaller of the 2.

The green and white wire from this harness needs to be quick spliced to a wire going to pin 3, and the orange yellow needs to be spliced to pin 6. get a spare 87-88 TC connector pigtail with about 5 inch of wire on it and you can add the pins from this, that way you dont have to hack up your harness, it also makers the wiring reversable. just tape off the pins you remove from the mustang harness, pin 3 is the power steering switch which is not used on the Turbo EEC, and pin 6 is not installed so you will need the extra TC CPU connector with wires to source extra pins from. I clipped mine out of a TC in the junkyard.

once the EEC sees the signal from the VSS you will have OD lockup. I also ran a wire an installed pin 42 and ran a wire to the transmission, I will eventually install a dual selinoid VB, so then I can compleate that wiring and essentually update the mustangs tranny."

Would that make it work?

 

[MrShorty]

I'm not sure what all the talk about the VSS is. Did your '87 originally have a VSS in it (My '87 BII had a VSS, so I would expect your '87 Mustang to already have ont)? If yes, then did you plug it back in when you put the newer A4LD in? If yes, then I don't know why we are discussing the VSS. If not, I don't know why the VSS in the '91 isn't/doesn't plug in. My impression was that Ford used essentially the same VSS across the board for those years.

My expectation, as far as getting TCC lockup to work is that all you should need to do is splice in a three prong connector with the correct two wires connected, and your existing computer should easily take over TCC control. But you still won't have 3-4 shift control.

If you can tolerate manual 3-4 shift control, the circuit is a simple ground-side-switched circuit. It would be pretty easy to wire in a toggle switch or something to control the 3-4 shift. Making it automatic is what would require changing over the computer or changing out the valve body.

 

[Ourobos]

My 87 has the VSS, and it's connected.. I think he's alluding to the 90-93 Mustangs, the same circuitry that controls the VSS, controls the electronic OD lockup... Where the 87-89 didn't have electronic lockup.. I simply want the tranny to shift normally, on it's own, from 1 to OD while driving down the road, the way it's supposed to.. I want this 92 tranny to do it, the easiest way possible for me.. Before I buy a 90 ECU and harness or pull the pan and work on the valve body, I may try his recommendation.. Thoughts??

 

[MrShorty]

I think he's alluding to the 90-93 Mustangs, the same circuitry that controls the VSS, controls the electronic OD lockup... Where the 87-89 didn't have electronic lockup

Still doesn't make sense to me, but it's probably mostly because I'm not understanding what he's trying to do. He talks authoritatively, like he's done this before successfully, so maybe it does work. If it does, I don't see how.

I pulled up wiring diagrams from Autozone.com for my '87 BII, my '92 Explorer, your '87 Mustang, and a '92 Mustang to compare. Where they share common elements, pin assignments appear the same, so I don't expect there are any huge differences between a Ranger A4LD and a Mustang A4LD.

Final analysis: IMO, it will be easier to swap the '87 valve body onto the newer A4LD than try to monkey with the wiring. As I said before, I'm reasonably sure that the valve bodies are swappable (if I'm wrong, someone correct me). Either that or make the necessary engine management changes and swap in a later model PCM.

 

[tmar04]

first post

Hello to all, This is my first post on this forum. I have a 1987 Bronco II, 2wd, AT and have no OD. Bummer!!

 

[tes0181]

Hi there please can someone help.I had a a4ld with 1 selenod burnt out and now I have a a4ld with 2 selenods how can I get this to work 2 pins into 3 does not go,thanks you for your help terry

 

[MrShorty]

tes0181:

A couple of options I can readily see. You could get a newer computer for your engine that will have the 3-4 shift solenoid circuit programmed in.

If you can tolerate manual 3-4 shift control, it would be relatively easy to wire in the 3-4 shift solenoid with a; toggle switch and control it manually.

 

[tes0181]

Buy a new car

Thank you for the help,have computor and a loom from old bronco.
so will change the parts thanks once again terry

 

[mihulka3]

Not all 88's had two solenoid.

The cutover was mid 1988 for the two solenoid setups. Unless you are counting mid 1988 built trucks being sold as 89's.