Has anyone bypassed the computer controlled lock up on the A4LD. Im looking at my trans upgrades and was thinking this would be useful to get some extra compression braking coming down hills etc.

I was just thinking of a simple toggle to activate the solenoid when I need it. I havent looked through the wiring diagrams yet, just looking for someplace to start.

Also looking for a mod list for the trans, from those who have done a performance upgrade(or as much of one as you can do). I have a list but am looking for ideas.

Let us know what you find out. I'm very interested...

how does the manual lock up torque converter work, err, how can it be used? could it be engagedunder full throttle? does it have to be dissengaged for the tranny to shift? im interested in it either way cause i often times cruise at lower speeds and would like to lock up the torque converter to get better gas milage.

Well, I dont have any info yet. The elect diagrams I have are fine, except they dont tell me which wires go to the 3-4 solenoid, and which go to the converter solenoid- they do tell me the color codes- its very strange. Looks like the hydraulic circuts require the 3-4 solenoid to be on also. What am I trying to say? Its more complicated than I first thought.

My Idea was to be able to switch it on in any gear so that I could use the engine braking more effectively and not slip my TC so much. If I can get it to work like I want you should be able to override the convertor lock up function and switch it on and off in any gear. So basically Im still trying to figure out the options.

Anyone have any ideas, or done this? Any and all help would be appreciated.

Gloria Rosen has done this to her explorer. I don't know if she's still on the list. She has it done at Doug's Transmissions in Arizona? New Mexico? I'm not sure. Do some forum searches, it's been discussed before.

Cheers

Dale

Dale,

Yea its always been discussed- with no details, that was the problem. I just havent called Doug, or his foreman or whoever to talk, and at some point it was posted that he (doug, etc) was tired of non business generating calls. Understandable.
I was hoping for a bone from someone who had theirs done. I have a shop that can do some work Im just doing some leg work for them- or at least thats my hope/plan. Im hoping to sit down with them and see whats what next month- see what we can come up with, and some $ figures.

from what ive read on the a4ld tranny is that it is a c3 trans. with a 2speed o/d unit put in front of it and it has a ELECTRONIC CONTROLLED torque converter, meaning it should just be a wiring mod and the trans. should have to be open up to install it, but thats just what ive heard

OKay here it goes. the A4LD is a 3 speed auto with an overdrive and an elctronically controlled hydraulic lock up convertor.

It is very simple.
There are two wires that go directly from the EEC to the A4LD shift solenoids. One is the signal for the 3-4 shift (OD) and the other is the signal for the lock up converter. The EEC computer bases the shift points on signals from the TPS, speed sensor, and other sensors.
When the EEC wants to shift to OD or lock up the conveter it sends a ground signal down to the shift solenoid(s) in the tranny. So it is simple. You wire in a relay or a simple switch to stop the signal from the EEC, let the EEC signal go through , or to send the ground signal yourself.

Now I do not have the wiring schematics here but I have them at home.
This will tell us what wire is what in the tranny harness.

Locking up the converter off road in 2nd gear may prove to be an effective mod!
Also disabling the lock up converter in town would help with some of the "searching" or "hunting a pecking" some A4LD's do (especially with larger tires, gear changes, mods to the valve body, converter, etc..)

Also bypassing the OD by use of a button instead of the shifter may help for those who dont want to use a OD floor shifter or aftermarket...I am using the floor shifter from a 84 BII 2wd with my 93 A4LD Explorer tranny. The shift linkage inside the tranny had to be swapped out, otherwise I would have to use a aftermarket (hurst) cable operated floor shifter, or convert my steering column over to the 89+ style :)

I did this (temporarily) about a year ago to diagnose some problems with my TCC clutch. Not difficult, do it like 410Fortune said.
According to the wiring diagrams at http://www2.autozone.com/servlet/UiBroker?ForwardPage=az/cds/en_us/0900823d/80/0b/a9/c7/0900823d800ba9c7.jsp, on the '91, the TCC lockup is controlled by a white wire coming out of pin 53 on the PCM connector.
As I recall from reading the transmission manual and doing this before, the TCC lockup is hydraulically inhibited whenever the transmission is in 1st, 2nd, or Reverse, so I don't think it's possible to get the TCC to lockup in those cases even with a switch. So it would only apply in 3rd or 4th gears.

I basically understand whats going on here, but also have a little confusion. It makes sense that the TC couldn't be locked it 1 and 2 and R, because in the case of a shift if the TC was locked it would seem like things would break. Even though it would be convenient I would be scared of doing this. So what this really would be used for would be making a push button overdrive lockout, and a full TC lock up in 3rd for 4th. This would be great because my tranny always seems to down shift (search) before what seems like my engine needs too because we live in a slightly hilly area.

So...to do what I said above, I would need um....

1) A non-momentary pushbutton switch (like on the end of the shift lever of 95+ Explorers) to control the 3-4 shift.... (This would be like putting the shift lever in D now, still allowing the TC to be computer controlled in 3rd).

and

2) A DPDT switch with off position for the TC solenoid. One on would patch through the signal from the computer, the other on would send a signal to lockup all the time, and the off would be unlocked all the time...

Is this all correct?
Am I right that the stock shifting could be kept?
What is meant by a ground signal, does that mean an open circuit, or a physical connection to the body into the input of the solenoid...

"What is meant by a ground signal, does that mean an open circuit, or a physical connection to the body into the input of the solenoid..."

Starting at the positive battery post, the current for the TC solenoid goes through the solenoid and into the computer. The computer has a switch inside that completes the circuit when it wants to turn the TC clutch on. That's all it means.

Ok thanks for clearing that up, I didn't think about it that way, but it makes sense...

So the TCC is locked when the solenoid is engaged, and the tranny shifts to 4th when the 3-4 solenoid is engaged correct??

Also where is the best place to tap into these wires.

Another question. Would having the TC locked, but the tranny being able to chose between 3rd and 4th be a bad thing. Seems like that shift would be harsh and break stuff. Is this right? I'm just trying to figure out whether or not I have to wire it so that it never shifts while the TC is locked.