strikefast
Member
- Joined
- May 18, 2006
- Messages
- 14
- Reaction score
- 0
- City, State
- Raleigh, NC
- Year, Model & Trim Level
- '92 XL
92 Explorer: No Overdrive 3/4 Solenoid bad or screen clogged?
I have a '92 Explorer 4x4 4.0L with the A4LD transmission. The overdrive isn't working, but the torque converter still locks in 3rd gear at highway speed with the gear selector in D (and OD, for that matter, but D just double-confirms that what I'm observing isn't the OD shift). There is no engine braking with the gear selector in 1, 2, or D. The transmission shifts and behaves fine otherwise.
I've read in other posts that one possible cause of the OD problem might be the 3/4 shift solenoid, or the wiring/signaling to it. (Thanks a TON to Glacier and MrShorty for their numerous posts on this topic!) Using the wiring diagrams on Autozone's website as a guide, I checked the 3/4 (and TCC) solenoids via the appropriate wiring harness that sits under the hood on the driver-side front fender well. Normal resistance of ~30 ohms was found across both solenoids. No leads were shorted to ground. So, wiring integrity seems to be OK.
The KOEO test returns 111 codes (all OK). I used the output state test to investigate further. It appears to me that the resistance between the purple/yellow and orange/yellow wires on the computer side of the connector and ground is ~70 ohms when de-energized, and drops to 0 when energized. This seems fine to me. KOER test also returns 111's. The red common from the computer side is supplying +12V.
Based on the output state test, it looks like the computer can signal the shift. As for whether it chooses to, that's more difficult for me to tell since I don't have a breakout box, etc. I don't know if it's realistic to hook up my cheap analog sweep multimeter to the computer wiring harness inside the passenger kick panel for a road test or not. Cruise control works, so I think the speed sensor is OK.
The results of the +12V click tests are quite interesting, in my opinion. I applied +12V to the common red lead. Results of grounding each of the following:
orange/yellow (3/4): audible click on de-energize, none on energize
purple/yellow (TCC): no audible click on either energize or de-energize
I feel 99% certain the TCC solenoid works based on my driving observations of torque converter lockup, even though I can't hear it "click" during the above test. This is interesting, because I expected the opposite results based on the symptoms (i.e., silent 3/4, and audible TCC solenoid). I have verified the results a few times. Does a click really mean that the solenoid is working properly? For example, I have had starter solenoids go bad on other vehicles where they would click loudly without actually energizing the starter...
In any case, I'm less inclined to think that the problem is electrical based on what I've done so far. To me, it seems more likely to be a mechanical malfunction in the solenoid, or something else wrong within the transmission.
My '92 was manufactured 10/91: I wonder if that makes it old enough to definitely have a screen around the 3/4 solenoid? If so, perhaps it is plugged as per Glacier's experiences... Does anyone know when Ford stopped using the version with the screen?
I realize that many other things could be causing my overdrive problems as well, but I was trying to focus on something short of a full overhaul/rebuild. Taking the valve body down to inspect/change the solenoid scares me a bit since I've never done any transmission work other than dropping the pan to change the filter/fluid and replacing the pan gasket. The thought of those check balls falling out and rolling across the floor turns my stomach!
I'm struggling to recall now, but it seems like there was a period of time where the OD struggled to engage before it stopped working totally. In other words, you almost had to let off the gas completely to get the OD shift, but my memory is faint there. Not sure if that might be indicative of a screen that was slowly getting plugged up...
I'd like to think that the lack of engine braking is not directly related to the OD issue, although I guess it could be. Fortunately, I don't live in a mountainous area, so I don't miss the engine braking ;-) I imagine that fixing the engine braking problem would almost certainly involve more serious transmission work. Neither OD nor engine braking have worked for at least 2-3 years now. I can't say whether both problems appeared simultaneously or not. Other than the modulator problem I also learned about on the site (and fixed), I've had no other trouble with the transmission and have treated it pretty well (no off-road 4x4 driving, light on the gas pedal, etc.)
Questions:
a) Is there any way to diagnose a plugged screen other than by visual inspection? In other words, I presume the electrical properties/tests would all check out "normal" in that case. Does the above sound like a scenario where this might be happening?
b) Any way to tell whether my 3/4 solenoid has a screen other than by visual inspection?
c) Can these transmission solenoids click, yet still be faulty?
d) Any point in further diagnosing whether the computer chooses to signal a 3/4 shift?
Sorry for the long post, but wanted to get all the available info out there in one shot.
Any advice or thoughts?
I have a '92 Explorer 4x4 4.0L with the A4LD transmission. The overdrive isn't working, but the torque converter still locks in 3rd gear at highway speed with the gear selector in D (and OD, for that matter, but D just double-confirms that what I'm observing isn't the OD shift). There is no engine braking with the gear selector in 1, 2, or D. The transmission shifts and behaves fine otherwise.
I've read in other posts that one possible cause of the OD problem might be the 3/4 shift solenoid, or the wiring/signaling to it. (Thanks a TON to Glacier and MrShorty for their numerous posts on this topic!) Using the wiring diagrams on Autozone's website as a guide, I checked the 3/4 (and TCC) solenoids via the appropriate wiring harness that sits under the hood on the driver-side front fender well. Normal resistance of ~30 ohms was found across both solenoids. No leads were shorted to ground. So, wiring integrity seems to be OK.
The KOEO test returns 111 codes (all OK). I used the output state test to investigate further. It appears to me that the resistance between the purple/yellow and orange/yellow wires on the computer side of the connector and ground is ~70 ohms when de-energized, and drops to 0 when energized. This seems fine to me. KOER test also returns 111's. The red common from the computer side is supplying +12V.
Based on the output state test, it looks like the computer can signal the shift. As for whether it chooses to, that's more difficult for me to tell since I don't have a breakout box, etc. I don't know if it's realistic to hook up my cheap analog sweep multimeter to the computer wiring harness inside the passenger kick panel for a road test or not. Cruise control works, so I think the speed sensor is OK.
The results of the +12V click tests are quite interesting, in my opinion. I applied +12V to the common red lead. Results of grounding each of the following:
orange/yellow (3/4): audible click on de-energize, none on energize
purple/yellow (TCC): no audible click on either energize or de-energize
I feel 99% certain the TCC solenoid works based on my driving observations of torque converter lockup, even though I can't hear it "click" during the above test. This is interesting, because I expected the opposite results based on the symptoms (i.e., silent 3/4, and audible TCC solenoid). I have verified the results a few times. Does a click really mean that the solenoid is working properly? For example, I have had starter solenoids go bad on other vehicles where they would click loudly without actually energizing the starter...
In any case, I'm less inclined to think that the problem is electrical based on what I've done so far. To me, it seems more likely to be a mechanical malfunction in the solenoid, or something else wrong within the transmission.
My '92 was manufactured 10/91: I wonder if that makes it old enough to definitely have a screen around the 3/4 solenoid? If so, perhaps it is plugged as per Glacier's experiences... Does anyone know when Ford stopped using the version with the screen?
I realize that many other things could be causing my overdrive problems as well, but I was trying to focus on something short of a full overhaul/rebuild. Taking the valve body down to inspect/change the solenoid scares me a bit since I've never done any transmission work other than dropping the pan to change the filter/fluid and replacing the pan gasket. The thought of those check balls falling out and rolling across the floor turns my stomach!
I'm struggling to recall now, but it seems like there was a period of time where the OD struggled to engage before it stopped working totally. In other words, you almost had to let off the gas completely to get the OD shift, but my memory is faint there. Not sure if that might be indicative of a screen that was slowly getting plugged up...
I'd like to think that the lack of engine braking is not directly related to the OD issue, although I guess it could be. Fortunately, I don't live in a mountainous area, so I don't miss the engine braking ;-) I imagine that fixing the engine braking problem would almost certainly involve more serious transmission work. Neither OD nor engine braking have worked for at least 2-3 years now. I can't say whether both problems appeared simultaneously or not. Other than the modulator problem I also learned about on the site (and fixed), I've had no other trouble with the transmission and have treated it pretty well (no off-road 4x4 driving, light on the gas pedal, etc.)
Questions:
a) Is there any way to diagnose a plugged screen other than by visual inspection? In other words, I presume the electrical properties/tests would all check out "normal" in that case. Does the above sound like a scenario where this might be happening?
b) Any way to tell whether my 3/4 solenoid has a screen other than by visual inspection?
c) Can these transmission solenoids click, yet still be faulty?
d) Any point in further diagnosing whether the computer chooses to signal a 3/4 shift?
Sorry for the long post, but wanted to get all the available info out there in one shot.
Any advice or thoughts?