Torque Converter clutch won't stay locked up

94 XLT with the 4ALD automatic with 185K, but completely rebuilt tranny about 10K ago. Lately strange things with torque converter lockup. It
usually works normally, with lockup right at 45 mph, and in and out like it should depending on load. If I stay under 55 or so, it is fine all day. If I get on the highway and cruise at 70 or so, it unlocks after about four or five miles, and then won't lock again - period, even if at lower speeds (but over 45). After a long shutdown, it again worked fine. This happened daily, whether warmed up to normal or not, but refused to do it for the tranny shop fellows after they fought with it for a whole day. So I took it home and it's doing it again. Lately, sometimes it doesn't lock at all when starting out in the morning (cold Michigan winter), so it's become less predictable and more intermittent. I assumed it might be something electrical (bad connector, etc.) but now it seems to be something sticking in the clutch activation mechanics. Do you think an additive might help, and then a drain, filter, etc. thereafter might help? Or is there something specific I should be looking for? Thanks.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
When operating properly, lockup occurs at 45 mph in 3rd or OD, whether right off the bat on a 10 below morning or fully warmed up on a warm day. Haven't checked MAF yet, but no codes on analyzer at shop (when they couldn't get it to not work properly). The rest "seems" ok, since it runs great otherwise. I was hoping there was somthing I might find since getting to the shop is a pain, since I teach ('cept today with a foot of new snow:-) Onward.....mush!
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Let me guess, CEL comes on if you are going about 65 MPH, or if you are coasting downhill? Can run all week, all day and not have problem until you get on the highway? Stopping ad turning off the engine, then starting again will turn the CEL light off and it won't come on again until you get back on the highway? If it all sounds familiar, let me know when you find an answer 'cause it's driving me crazy.
| 94 XLT with the 4ALD automatic with 185K, but completely rebuilt tranny | about 10K ago. Lately strange things with torque converter lockup. It | usually works normally, with lockup right at 45 mph, and in and out | like it should depending on load. If I stay under 55 or so, it is fine | all day. If I get on the highway and cruise at 70 or so, it unlocks | after about four or five miles, and then won't lock again - period, | even if at lower speeds (but over 45). After a long shutdown, it again | worked fine. This happened daily, whether warmed up to normal or not, | but refused to do it for the tranny shop fellows after they fought with | it for a whole day. So I took it home and it's doing it again. Lately, | sometimes it doesn't lock at all when starting out in the morning (cold | Michigan winter), so it's become less predictable and more | intermittent. I assumed it might be something electrical (bad | connector, etc.) but now it seems to be something sticking in the | clutch activation mechanics. Do you think an additive might help, and | then a drain, filter, etc. thereafter might help? Or is there something | specific I should be looking for? Thanks. |
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
No lights. Everything looks normal. Stopping vehicle and restarting engine will not cause TCC to operate properly once it unclutches at highway speeds. It usually will be ok after a longer "cooldown", but lately it doesn't always. Now it's starting to act up at "normal" speeds (ie., 50-55) - - but not always. Driving me crazy, too! Stay tuned.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
John Riggs wrote:

are
until you

again
back on

'cause
tranny
It
fine
again
not,
with
Lately,
(cold
and
something
I went through this a while ago, and finally figured out that I had a leaking spark plug wire that was causing the problem. It took a bit of careful step-by-step sleuthing but I finally figgered it out after replacing a lot of stuff that needed to be replaced anyway. That's my storya dn I'm sticking to it.
Seriously, I get about 50-60k from a set of wires then they start to break down. Shows up first under towing load, and gets worse over time. The miss from the failing ignition is just enough load change to cause the trans to shift out of lockup for a few seconds, then back in. Try a set of wires. They are cheap (<$30) and not too tough to replace in less than an hour.
Hope this helps!
dr bob
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Good shot at it, dr bob. And I believe it. But she's running strong with new plugs, wires, etc., and the odd thing is that once it unlocks on the highway, it will not lock up again all day - on or off the highway - until it sits at least overnight. Then it's (usually) back to normal operation as I described earlier. That "normal" is a very firm shift pattern, and solid lockup at 47 mph.
Now it's unlocking more often at lower, steady, speeds. I'm starting to suspect temperature sensors. So strange!
I'm almost tempted to put in a switch to activate the selenoid when it unlocks and sticks me with higher revs on a highway trip. I think that can be done without overriding the brake cutout, etc. Ultimately, there are three ways for the selenoid to operate: computer, manual switch, pressure activated switch (requires some careful drilling and tapping). Trouble is, if I ever sell it, I have to give a training session:-)
Before I get to far, I'm waiting for warm weather and see how it does. No fun trying to crawl around at 15 degrees in a blowing snow or wet garage floor.
Hmmmmmm
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
It sounds like you and I are headed in the same direction with this. Now, if I have to decelerate over a long, distance of a couple thousand feet, it will darned sure flash my CEL, and similar if I am in downtown, stop and go traffic. You may not think this is a related problem, but I'm betting odds that when you find an answer, then I will have an answer. Temperature was next on the list of things to check ( did you notice we have no way to check tranny temp? ). I wonder if there is a way to check this out.
| Good shot at it, dr bob. And I believe it. But she's running strong | with new plugs, wires, etc., and the odd thing is that once it unlocks | on the highway, it will not lock up again all day - on or off the | highway - until it sits at least overnight. Then it's (usually) back to | normal operation as I described earlier. That "normal" is a very firm | shift pattern, and solid lockup at 47 mph. | | Now it's unlocking more often at lower, steady, speeds. I'm starting to | suspect temperature sensors. So strange! | | I'm almost tempted to put in a switch to activate the selenoid when it | unlocks and sticks me with higher revs on a highway trip. I think that | can be done without overriding the brake cutout, etc. Ultimately, there | are three ways for the selenoid to operate: computer, manual switch, | pressure activated switch (requires some careful drilling and tapping). | Trouble is, if I ever sell it, I have to give a training session:-) | | Before I get to far, I'm waiting for warm weather and see how it does. | No fun trying to crawl around at 15 degrees in a blowing snow or wet | garage floor. | | Hmmmmmm |
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Come to think of it, John. Long ago, and before the tranny rebuild, my CEL would come on when running at high speed in the mountains or when towing. On-off-on-off all day and night on a long trip. Get back to flatlands or unhook the tow, and no more light problems. Same thing after a long deceleration. Only at higher speeds and/or with a tow.
I'm not sure if this is related to my problem, exactly, but interesting.
I think that there is some sensing problem - related to temperature "differentials". I didn't notice the problem before winter (tho it may not have been there before winter), and how and how long I warm the vehicle up seems to make a difference when, or if, the lack of lockup, or unlock occurs.
Then again, it could be a bad electrical connector that is temperature/moisture critical. When the tranny guys plugged in their analyzer, they couldn't get the problem to occur. Hmmm. Maybe it's in that connector (I'll check tomorrow). Or a sticking selenoid that is sensitive to a cold case and warm fluid, etc. I'm just doing the usual "looking for an easy way out" before getting too deep into shop expenses with an old but nice vehicle.
By the way, probably pretty easy to install a temperature sending unit in the tranny. Lots available on that elsewhere.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Just a quick aside, John. I used to know a sailor named John Riggs who sailed the Great Lakes in Michigan. Not a chance, I bet, but worth asking.............
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I went to boot there, but I was assigned to the U.S.S. John F. Kennedy before I transferred to the U.S. Army.
| Just a quick aside, John. I used to know a sailor named John Riggs who | sailed the Great Lakes in Michigan. Not a chance, I bet, but worth | asking............. |
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Oops. Meant recreational sailing and cruising on the Great Lakes around Michigan. I was US Army 67-70 and wish I had been on the Kennedy. Less mud:-)
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Hey dr bob. Try this on for size. As fussy as I am, and careful about service, I checked my radiator and found my coolant down almost one gallon. The plastic overflow tank had a stain that I took for the fluid level, but it was empty. How I let it go this long, I don't know. Anyway, I'm thinking that it's really possible that this was causing the tranny problems. There may be a temperature sensor that was getting either 1) no coolant to it, or 2) only steam to it. Could this possibly give mixed signals to the computer and cause the TCC problems? My temp guage operated properly in the normal range. I haven't had a chance to go out and test drive it, but will tomorrow and see if the problem cleared up. I will also try to find out where the coolant is going. I know it's not going into the transmission, and don't suspect the engine, either, but likely a slow leak radiator-wise. Whatever is is, it's realively slow.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Let me know when you get an answer....I want to know this one too ('92 EB)
| Hey dr bob. Try this on for size. As fussy as I am, and careful about | service, I checked my radiator and found my coolant down almost one | gallon. The plastic overflow tank had a stain that I took for the fluid | level, but it was empty. How I let it go this long, I don't know. | Anyway, I'm thinking that it's really possible that this was causing | the tranny problems. There may be a temperature sensor that was getting | either 1) no coolant to it, or 2) only steam to it. Could this possibly | give mixed signals to the computer and cause the TCC problems? My temp | guage operated properly in the normal range. I haven't had a chance to | go out and test drive it, but will tomorrow and see if the problem | cleared up. I will also try to find out where the coolant is going. I | know it's not going into the transmission, and don't suspect the | engine, either, but likely a slow leak radiator-wise. Whatever is is, | it's realively slow. |
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Got an answer this morning when I drove to work. Outside temp about 45 degrees. TCC locked up right away at 47 mph. About 5 miles down the road it unlocked, and would not lock again. So here we are............square one.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I may have found the problem and fixed it. As I was going into town today, the TCC unlocked again. I redirected immediately to my transmission shop and they attached the code reader and analyzer. It came up 186, I believe, and they said that was showing a problem with either the Throttle Position Sensor (TPS) or the Mass Air Flow Sensor (MAF). I went home an checked out the TPS (OK), and removed the filament block for the MAF and found them severely caked with dirt and gunk.
Having cleaned the filaments before when the engine was pinging and not running properly, out came the Throttle Body Cleaner and my small, soft artists brush. I very carefully cleaned the filaments and reinstalled the block and connectors. After a test drive the transmission appears to shift properly and lock up right on schedule - and stay locked up while cruising. I'll give it another shot tomorrow on the highway.
I wasn't aware that the MAF signal affected TCC lockup, but they say it's part of the mix of data used. I'll follow up in a few days and let you know if that did it for sure.
(If this is a duplicate, it's because I had a problem posting it the first time - sorry)
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Looks like the dirty MAF sensor was the curprit. Lockup is fine now. Lost the spark knock/rattle, too. Oh yeah, loose radiator hose clamp was the problem with the coolant loss. Dribbled down to a crossmember and dispersed, so it never showed up on the garage floor. Whew. All set for another 190,000 miles............
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Thanks for posting the resolution Craig.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Just wanted you all to know that it has been a week, two long highway trips, and a lot of other local driving. No more problems.The MAF sensor was absolutely the problem, and cleaning it resolved the problem. Now if I could just find out how I screwed up my cruise control (posted elsewhere).......
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Just for the sake of argument, what is wrong with your cruise control?
| Just wanted you all to know that it has been a week, two long highway | trips, and a lot of other local driving. No more problems.The MAF | sensor was absolutely the problem, and cleaning it resolved the | problem. Now if I could just find out how I screwed up my cruise | control (posted elsewhere)....... |
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.