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.

--
x-no-archive: yes

I'm just on my way out the door and I'm going to quote memory (and we'll
have to trust that I will remember to double check later). I'll need to ask
what steps were taken to determine that the concern was the TCC unlocking?

I ask since the TCC is not supposed to lock if the engine temp shows cold.
Engine load will unlock the TCC... a dirty MAF, insufficient fuel flow,
faulty TPS and inappropriate EGR flow are some of the things that can
affect load computations. A problem with the BOO switch can unlock the TCC
and I'm sure there are a couple I'm forgetting.

I can only suggest that your tech familiarizes himself with the operating
strategy of the TCC.


"Craig" > wrote in message
oups.com...
> 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.
>

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.


"Craig" > wrote in message
oups.com...
| 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.
|

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!

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.

John Riggs wrote:
> 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.
>
>
> "Craig" > wrote in message
> oups.com...
> | 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.
> |

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

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

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.


"Craig" > wrote in message
oups.com...
| 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
|

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.

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.............