Can you help me diagnose my A4LD OD issue?

[ErockSteady]

Hello experts!

I recently bought a 93 XLT with the A4LD. I recently discovered (not while test driving!) that OD is not behaving properly. I've read many threads on this forum, but I can seem to find the exact diagnosis of this problem. If it's out there and I missed it, I'm sorry.

My symptoms:
1) All shifts seem fine and smooth 1-2, 2-3, 3-4
2) In 4th gear, no OD seems to happen; no RPM drop, nothing audible, etc
3) D and OD behave exactly the same (both go through all 4 gears)
4) When going about 55-60 mph, my RPMs are at about 2,700 - 2,800
5) When going 55-60 mph, shifting from OD to D, there is a *very* slight clunk felt, but no RPM rise. When shifting from D back to OD, nothing happens at all.

Any ideas on what the issue could be? I'm getting ready to go on a 400 mile trip pulling a small trailer, so I'm not too worried about it since I wouldn't use OD anyway, but I'd like to know what's wrong. Since D and OD both behave the same, I'm assuming the A4LD's overdrive isn't a true extra gear, correct?

Thanks all!

 

[BrooklynBay]

It's an actual setting, and not a virtual setting like that of the 5R55E transmission. Do you have any codes with a check engine light? There are many factors which could prevent overdrive from engaging. Did you check the overdrive solenoid, wiring, and the computer output while driving with an LED snaked into the cabin area? The output from the computer is a ground connection when overdrive engages. The 3 prong connector has a constant 12 volt source while the vehicle is on.

 

[ErockSteady]

It's an actual setting, and not a virtual setting like that of the 5R55E transmission. Do you have any codes with a check engine light? There are many factors which could prevent overdrive from engaging. Did you check the overdrive solenoid, wiring, and the computer output while driving with an LED snaked into the cabin area? The output from the computer is a ground connection when overdrive engages. The 3 prong connector has a constant 12 volt source while the vehicle is on.

No, I have no check engine lights, and so I haven't checked any codes. Also, I know next to nothing about automatic transmissions, so I'm not sure how to check the overdrive solenoid, wiring and the computer output. How do I get at the OD solenoid? Drop the pan? Then what am I looking for when I check it? Also, how do I go about checking the computer output? Sorry...very basic questions I know.

Additionally, please set me straight here: is 4th gear overdrive or not? I've read in a few different places that in the A4LD, 4th gear *is* overdrive. I'm definitely getting into 4th, but I'm confused, because I get into 4th in D and OD, and they behave no differently from each other.

Also, like I said in my first post, there is a very slight clunk when going from OD to D, but no RPM rise. What is that? Something is happening, or trying to happen...

Sorry for all the questions! I'm such a noob when it comes to ATs. Thanks!!

 

[ErockSteady]

So after doing some more reading, I guess what I'm dealing with is a torque converter that is not engaging.

Now I have to decide do I drive the Ex as-is for this 400 mile camping trip pulling the small trailer, or quickly put a trailer hitch on my Dodge Caravan (neither seems like the ideal option). I wouldn't be using OD anyway on this trip, but would the TC not locking in 3rd be an issue?

 

[BrooklynBay]

The 3-4 shift & TCC solenoids are mounted on the valve body. There is a 3 prong connector on the top driver's side of the transmission. Each solenoid should read 25 - 40 Ohms.

 

[ErockSteady]

So is driving around without having the TC locked a big deal? I'm about to embark on a trip pulling a small trailer. I'd be around 3k RPMs at highway speeds for about 200 miles one-way.

Also, after thinking about this more, I shouldn't have said I'm getting into 4th gear. All I really know is that I'm going through 3 shifts in D and OD; that I know for certain. Both act like no TC lockup (high RPMs, no drop when hitting the brake, rapid drop-off when letting off accelerator). However, if everything is working as it should, 3 shifts in D should mean I'm in 3rd locked right? And 3 shifts in OD should mean I'm in OD unlocked. Do I have this right? I'm baffled then, as to why D and OD both behave identically...

 

[BrooklynBay]

Do you have LEDs installed as brake lights? There is a known issue when using them on a Ford vehicle. The LEDs don't allow the circuit to drop down to ground since they have high impedance.