No OD

[Bullmastiff9]

Hello to everyone! Glad to be a part of this site and hopefully I can help others and receive some in return.

Sorry to say, that I am in need of some help right away. I have a 1991 Explorer XLT with around 115k miles on it. I recently swapped out the transmission fluid. Everything went about as well as could be expected. However, since the swap, I no longer have OD.

I knew the Explorer leaked fluid when I got it, so I checked it fairly often until I bought a newer vehicle. After that, I'm sorry to say that I neglected it. So, when I drove it again, it constantly shifted between 3 and 4. Eventually I rarely drove it and when I did it barely moved at all. I attribute this to an extreme loss of ATF. When I did the swap, I was not surprised to find a near empty pan. After the swap, all the other gears shift smoothly, but it just doesn't shift into OD. I was told this could be caused by loose wires or a broken solenoid inside the pan.

Does anyone have information on how to check the wiring to the solenoid without dropping the pan off again? Or, if I do drop the pan off, what am I looking for?

I'm just not sure how to go about starting this repair.

Thanks in advance for any help!

 

[MrShorty]

I know I've posted information for checking the electronic controls on the A4LD before. You might try to find it, as it will have more detail than what I will post now.

1) Start by pulling codes from the computer and resolving any problems the computer can see.
2) To test if the computer can command the 3-4 shift, Perform the output state test while monitoring the voltage drop across the shift solenoid. I've found that the wiring diagrams in Chiltons (or the vehicle repair guides at www.autozone.com) are adequate for this operation.
3) To test if the computer chooses to command the 3-4 shift, perform a road test while monitoring the voltage drop across the shift solenoid.
4) The circuit itself is a pretty simple DC circuit. One could easily test for continuity through the solenoid with an ohmmeter. Just make sure you have the solenoid isolated from the main computer when you do. I've heard that it is possible to damage solid state circuits by measuring their resistance.

 

[BrooklynBay]

I saw this tread after responding to your other identical thread. A digital multimeter usually has a very high impedance which is ideal for testing sensitive electronic circuits. Most, but not all analog multimeters have a much lower resistance, and are not recommended. You could use 12 volt LEDs such as the kind they use for alarm systems to indicate when your 3-4, and TCC solenoids are being commanded by the PCM. This could be your diagnostic indicators while driving.

 

[Bullmastiff9]

Sorry about the multiple posts. I wasn't sure where the best place for it was. I finally found this transmission section and figured that's where it was supposed to go.

I'm really new at this stuff so you're going to have explain things a little more for me. I've worked on cars before, but not at all on transmissions. They were kind of a black box for me, so to speak. Swapping the fluid was the first time I've ever done anything with a tranny. I have the Hayne's Repair Manual and haven't found anything in it to help me yet.

My thinking was to pull the pan off and check continuity across the solenoids. And, correct me if I'm wrong, the solenoids are on the passenger side closest to the front of the vehicle?

 

[NHale623]

You shouldn't even have to drop the pan to check the solenoids, unless you really want to.

Just disconnect the transmission wiring harness and test from the connector on the transmission case. Do you have the resistance specs for the solenoids?

If you go up to the sticky threads at the top of this forum, the thread "Downloadable FORD factory repair manual info" will point you to a site that has the Ford manuals online that you can pull down and install on your PC. I don't think '91 is listed, but you can download the '93/'94 manual and it will have everything you need for the A4LD transmission.

 

[BrooklynBay]

The resistance should be within 25-40 ohms. The connector is located on the driver's side of the transmission. It has 3 prongs, and is vertical. There is a clamping diode in the connector. The connector has a constant positive voltage (ignition controlled). The solenoids engage when the PCM applies a ground (negative voltage) to them.

 

[Bullmastiff9]

Oh, alright. That will save me some time by not having to drop the pan. I'll have to get a multi-meter and check that.

So, I have to disconnect it and check the resistance across the prongs?

Once again, I want to apologize for sounding slow in the head. I appreciate the help and patience you guys are showing.

 

[BrooklynBay]

You could check AutoZone for a schematic diagram, and check the solenoids directly from the computer's wiring harness so you don't have to climb under the truck.