My torque converter lockup will sometimes go in & out of
lockup went cruising down the highway under light load,
it does this when in overdrive & it seems to still do it when
I turn the O.D. off. It does not shutter or vibrate when going
in & out I just see the tach jump up about 350-400 RPM's, if
I speed up or go up hill it will stay in lockup untill the load
goes down, then will unlock again. I know that when the trans
is real cold it is not suppose go into lockup untill the trans
warms up some. This is hapening in warm weather with the
trans warmed up, is there a temp sensor that might be messing
up sometimes or something else maybe?????????(this is on my
1996 f250 351 with 90,0000 miles) it does not always do this,
any ideas??????????

 

This is not uncommon for the converter to lock/unlock at tip-in/tip-out throttle conditons. This keeps transmission jarring to a minimum.

Are you the original owner of this truck?

 

Practically Yes, I bought the truck from my Dad with
8,000 miles on it. I have never seen the trans do
this before though. It would always shift into O.D.
then go into lockup & stay there until it would
shift back into 3rd gear if needed.

 

The shudder you're experiencing is most likely from a torque converter going bad. A bad converter has the potential to take out the rest of the transmission so diagnosing/replacing it can help keep repair costs to a minimum and save the rest of the transmission.

 

if you have shudder try changing all the fluid including the t.c and a new filter.

 

There is not any shutter at all, I think u misread my post,
It goes in & out of lockup very smoothly!!! I have had
the trans & t.c. machine flushed with a new filter once at
about 50,000 miles.

 

any other idea's?? temp sensors/other sensors etc?? anyone!!

 

Hi,
I know this thread is many years old, but I have the exact same issue with my E4OD trans. The vehicle is an 1993 E350 RV 7,3 IDI, but the problem described in the OP is exact the same as mine, so I tyr this forum as well.


It goes out of lockup for appr 1-2 Seconds, and then back into lockup again. Happens both in 3.rd and 4.th gear, only at steady speed. It happens randomly on longer trips, sometimes several times in 15-20 minutes and then no issues for 2 hours. I do not find any pattern. Engine temp is fine, trans temp is fine, outside temp can be anything.


I have changed the VSS and rpm sensor but no luck. But I have isolated the cause for the problem to be outside the trans by making a testlight flashing whenever the lockup turns off by tapping into the wire on the trans harness. This meaning there is a signal going into the trans telling it to unlock. If the cause was inside the trans, I would not get a light in the testlight. I have also changed taillight and brake light bulbs, and changed the brake light switch, but still no Luck.


I have had this problem for 2 years now, but I do not find the cause for the problem.


Appreciate alle the tips and help I can get.


//Lars Petter
Norway

 

i would have the op start here:
https://www.ford-trucks.com/forums/1...s-harness.html

larspetter,since your control unit is telling the converter to unlock (verified via test light) when it shouldn't,is your speedometer and tach reading steady?
do you have a tach gauge in that thing? if not,search the idi section on how to test the tach sensor.this might be faulty.it's pretty basic,you just inspect the wires and pull it.measure it's resistance while holding it up away from metal and it should be like 2k-3k ohms if i recall.

are you getting anything for helpful codes other than 62?


lets go pats!

 

I have no blinking OD lamp so I assume that means no codes either. I have already replaced the rpm sensor. I have no tach in my vehicle, but the speedo is acting normal, no jumping. Also checked the harness plug ann connector on the trans. Is there anyway of testing the TCU itself, or could it be a poor ground somewhere interrupting?

 

Usually it is a throttle position sensor (usually called the FIPL - Fuel Injection Pump Lever) sensor that is failing. The failing sensor will send data that you are quickly moving the throttle a large amount when you are not, and this causes the converter to unlock.

 

Hi Mark,
I do not think that the FIPL (TPS) is the cause, because if that sensor was failing, I would not get a signal coming from outside the trans, witch I do on the test light I connected to the lockup signal wire in the trans harness.


I only use the RV in the spring and summer time, so for now it sits out in the cold for another 3 months. But I try searching for others that had the same issue (as the OP), and see if anyone found a solution.


I am running out of ideas of where to look on the vehicle itself. Replaced VSS, RPM sensor, NSS switch, brake light switch, tail (brake) light bulps. I am kind of convinced that it has to some kind of electrical issue, but I dont know where to look for it. Maybe I should try to replace the complete wire harness going from the TCM to the trans? Maybe there is a short to ground somewhere, or maybe a poor ground connection?

 

You're the transmission expert, I just try to help by telling people about failures I've seen in my 30+ year automotive experience. If you don't want to look into what I've seen happen before that's your choice.

Your reply to me shows that you don't know how the PCM uses the TPS signal. So keep looking for your problem. You're bound to find it sometime. Good luck.

 

Hi Mark,
Didn`t mean to offend your experience and disrespect your advice, I appologise for that. And I am by no way any transmission expert. Beeing a non-expert, for me it did not make locic that a sensor on the trans was giving a signal back to the PCM, and then back to the trans again via the main harness. Will a failing TPS cause this random lockup off/on? Reason for asking is that I experience that sometimes it happens several times in maybe 15-20 minutes, and then nothing for the next hour or two. Please baer with me, I need all the help I can get, and I absolutely respect your automative knowledge.

 

The TPS is on the engine, not the transmission. The PCM reads it to see how far down you've pressed your right foot.

As the sensor ages it gets worn spots. This changes the reading from a steady increase as you press the pedal to a non-linear trace. The PCM sees this non-linear portion as a quick movement of the pedal, which will cause an unlock. This is a very common problem on the older 7.3L engines such as yours.