How to tell if the converter is locking up on a 1993 Explorer | Ford Explorer Forums - Serious Explorations

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How to tell if the converter is locking up on a 1993 Explorer

TrackAire

Member
Joined
February 16, 2020
Messages
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City, State
Vacaville, California
Year, Model & Trim Level
1989 Bronco II
Just picked up a 1993 Explorer 4x4 with 3.27 gears, auto and the stock size 235/75/15 tires. On the highway at a constant 65 mph the tach shows around 2200 rpm. How can I tell if the torque converter is locking up?
The RPM's seem just a little high to me. I've tried touching the brake while holding a steady 65 mph but no change in RPM. (I have other cars that unlock the converter when I do this).

Any other way to tell if the transmission is locking up the torque converter in 4th gear?

Does the coolant temperature have to be at a certain level before the computer allows the converter to lock up?. I do not believe my coolant gauge is working and have it scheduled to be check by a mechanic on Wednesday. When I bought the truck I used a thermal scanner after a long test drive to check the upper radiator hose and the coolant seem pretty cool (like 160 degrees).

I've done some forum searches but I'm not finding a way to test while driving without tapping into wires on the solenoid, etc.
 



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Check this thread:

a4ld lock-up clutch won't engage



If that doesn't help use our Google search bar near the top of each page and search for A4LD lockup. There are several threads and several issues that can cause a problem with the TCC.
 






Check this thread:

a4ld lock-up clutch won't engage



If that doesn't help use our Google search bar near the top of each page and search for A4LD lockup. There are several threads and several issues that can cause a problem with the TCC.

Ok, thanks for the link and google search suggestion. After more searches this may be a engine coolant issue. My ECT gauge barely moves off cold, even after a long highway drive. I'll have my mechanic check it out on Wednesday. Does anybody know what temperature the engine/coolant has to be at before the torque converter will actually lock up? Of course, this is assuming that the lock up feature is tied to the ECT. I did find a thread where the trans would unlock when the ECT got too hot so maybe it is ECT controlled.
 






I'm going to move your thread to our transmission forum. It may get more response there.
 






This is the principles of the lock up operation.
2A515C6B-BA02-4A18-A90B-34544456056E.jpeg
 






Brad,
Thanks so much for those operational instructions, I'm taking them to my mechanic right now. I'm thinking I may have an issue since the coolant gauge is not working (maybe not showing 128 degrees to the computer)....hopefully that is all it is. Both the coolant gauge and voltmeter are getting fixed today. We will also be changing the trans filter (I believe this is possible, checking with the mechanic).

Once I get the truck back I will have some more questions on what to do service-wise on the trans in regards to tightening bands, etc. The vehicle has under 77k miles but I have no idea how the truck was serviced. I just want to do whatever I can service-wise to insure reliable service.
 






This is the principles of the lock up operation.
View attachment 179267

I just got the truck back from the mechanic and we replaced the following parts to bring the truck up to reliability standards. New radiator, all new coolant and heater hoses, new thermostat, both temp sensors and a new serpentine belt were replaced. We also serviced the transmission. The trucks coolant gauge finally reads what I consider normal (stays right around the "O" on the word normal on the gauge), before it would barely register anything. The transmission definitely shifts very nicely through all 4 gears and cruises at around 2300 rpm at 65 mph (3.27's and stock tires). So I'm around 300 rpm higher than I should be because it is not locking up.

But, if I accelerate very briskly up to highway speeds, the unit will kick into 4th gear converter lock up and I'm right around 1900-2000 rpm at 65 mph which is where my calculations show it should be. If I accelerate at a normal pace up to highway speeds it will not go into converter lock up.

I can repeat this over and over.....normal acceleration, no lock up in 4th gear. Drive it like I stole it, it locks up once in 4th gear.

I've read the "converter clutch operation" flow chart you posted above and if it's not something simple it looks like it can be either an electrical or hydraulic issue. Sounds like a transmission specialist may be needed.
My concern is I may be overheating the transmission by driving it for long distances due to no converter lock up.

Any other ideas would greatly be appreciated.
 






Any other way to tell if the transmission is locking up the torque converter in 4th gear?

Does the coolant temperature have to be at a certain level before the computer allows the converter to lock up?. I do not believe my coolant gauge is working and have it scheduled to be check by a mechanic on Wednesday. When I bought the truck I used a thermal scanner after a long test drive to check the upper radiator hose and the coolant seem pretty cool (like 160 degrees).
Once again, Ford engages highest gear first, 4th. in your case, then locks the TCC. If TCC is locking, you can easily determine it at speed, ~ 50 mph on level road, cruising constant speed, no hills, by LIGHTLY increasing gas pedal pressure slowly. If locked, tachometer will remain steady , as the system acts like a MANUAL clutch is present. If not locked, tach will immediately jump up as torque converter begins to "slip"
 






Once again, Ford engages highest gear first, 4th. in your case, then locks the TCC. If TCC is locking, you can easily determine it at speed, ~ 50 mph on level road, cruising constant speed, no hills, by LIGHTLY increasing gas pedal pressure slowly. If locked, tachometer will remain steady , as the system acts like a MANUAL clutch is present. If not locked, tach will immediately jump up as torque converter begins to "slip"

Yes, I can definitely tell that the converter is now locking at freeway speeds in 4th gear and when it locks up, it is very obvious....but it will only lock up if I accelerate very briskly through the gears. If I just get on the freeway at normal acceleration speeds, it will not engage the converter lock up clutch no matter how long I drive at a constant speed (say 65 mph on flat ground).

I've done this multiple times attempting different driving and rpm applications to see what it takes to lock it up once I'm at freeway speeds and the results are always the same. No lock up in 4th unless I play Speed Racer getting up to speed.
 






Yes, I can definitely tell that the converter is now locking at freeway speeds in 4th gear and when it locks up, it is very obvious....but it will only lock up if I accelerate very briskly through the gears. If I just get on the freeway at normal acceleration speeds, it will not engage the converter lock up clutch no matter how long I drive at a constant speed (say 65 mph on flat ground).

I've done this multiple times attempting different driving and rpm applications to see what it takes to lock it up once I'm at freeway speeds and the results are always the same. No lock up in 4th unless I play Speed Racer getting up to speed.
Do you have trouble code(s)? W/O them, it's spearing minnows in a barrel. Is acceleration feel of the vehicle normal? The engine load and speed is added in when locking TCC. We have a 12 mile grade here on which the speed limit is 65; the TCC WILL NOT lock going up that hill, no matter what, on my '04.

One other fact is, Fords infinite wisdom UNLOCKS the TCC if locked, whenever gas pedal is completely released (coast), regardless of anything else. This is why I maintain the TCC solenoid is the first to fail: excess cycling by those drivers constantly on and off the gas. I cannot absolutely confirm that your earlier gen works identically, but have no reason to think otherwise.

RE: Engine Coolant Temp.: TCC WILL NOT LOCK with a cold transmission, gen 3; might use ECT Sensor in gen
Yes, I can definitely tell that the converter is now locking at freeway speeds in 4th gear and when it locks up, it is very obvious....but it will only lock up if I accelerate very briskly through the gears. If I just get on the freeway at normal acceleration speeds, it will not engage the converter lock up clutch no matter how long I drive at a constant speed (say 65 mph on flat ground).

I've done this multiple times attempting different driving and rpm applications to see what it takes to lock it up once I'm at freeway speeds and the results are always the same. No lock up in 4th unless I play Speed Racer getting up to speed.
"My concern is I may be overheating the transmission by driving it for long distances due to no converter lock up."

This I personally would not be worried about. The TCCs were added to gain MPG, not reliability. After all, we drove without TCCs for nigh onto 80 years.......If I were to guess by your description, it would be a hydraulic/mechanical problem with the TCC itself, not likely PCM scheduling or hydraulic flow to the TCC. Look for codes!
 






IMP,
Thank you for the additional info and I'll look for codes and dig a little deeper. One reason I'm trying to make the torque converter lock up feature work is this truck is scheduled for 4.88's and for highway travel the lockup feature appears to drop the rpm approximately 300 rpm. I'm going to be slightly over geared but when loaded and going into the Sierra's I'd figure I will live with the additional highway RPM to make things easier on the truck. I'd rather go slow and steady up the mountain than lug the stock 4.0.
 






Here is some more areas to check.
8918B9F7-DA10-4C2A-8D94-DBE0EA0C716E.png
 






IMP and Transman304,
Thanks again for all the input. I was delayed moving forward fixing my transmission issue due to losing a radiator, then a water pump and then the COVID-19 stuff....but I just pickup up a code reader (great, easy to use item) since I now have 3 vehicles with OBD1 diagnostics.

I ran trouble code test on the 1993 Explorer and got a code 536 (Brake On/off "BOO" circuit not activated during KOER) and a code 629 (Converter clutch solenoid circuit fault or lock-up solenoid circuit fault).

I think the code 536 is because I didn't activate the brakes during the test. But, I just double checked the brake lights and they will not turn on when I step on the brake pedal. (I know for a fact they did when I bought the truck as this was on the pre inspection checklist I did). The running lights, emergency flasher and turn signals all work, just no brake lights. So according to Transman304 checklist, this may be the issue....I definitely have to fix it one way or another.

But code 629 is definitely the next thing to tackle. I'm not sure if the brake issue is causing it to throw this code or it is another issue on its own.

I'll get to work on trying to fix the brake light issue....any other input is always appreciated.
 






Good to hear, the 629 code is going to be a piggy back to the 536 more than likely. Thanks again for the update.
Brad
 






Just had the vehicle diagnosed and code 629 fault was correct. Transmission shop replaced the converter clutch solenoid and the system works perfect now.

Just a couple things to fix now....A/C and for some reason the cruise control stopped working a couple of weeks ago. Once those two things are fixed, it's time for the modifications to begin.
 






Glad to hear that you got it repaired. Thanks for the update.
Brad
 






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