i had hockey games all this weekend. an hour drive each way. on the way back today the torque converter started unlocking then locking back up going down the highway at 65-70. it started getting worse, the converter was unlocking every 15-20 seconds then locking back up each time. then i started going threw some small (blink and miss towns) and i stopped and went numerous times, stop signs, stop lights and such and it started to get better. but on the highway it was terrible, i was running at a constant speed. when i drive it local it's fine. what the hell is going on?? od button doesn't blink either. any input would be appreciated. thanks, pete

 

How many miles on the truck?

Is it a factory build?

Have you pulled any codes yet?

 

You have a bad ground in one of your brake/tail lights. A stray voltage from a clearance or tail light that has a bad or dirty ground will send power down the brake light wire- signalling the PCM to unlock the TC. I would bet money on it. Been there done that.

 

truck has 251,xxx miles on it. don't know if it's been rebuilt or not.

 

your telling me i need to find the grounds, un screw them clean em up and put them back together? thanks, pete

 

Brake lights activate the TC unlock...... don't rest your foot on the brake. Check the rear tail lights for bad bulbs...... post back.

 

Pete,

Yes I went thru the same problem on my dads 92' F250. His bushing that connects the brake predal to the master cylinder rod was so worn that sometimes the brake switch would flicker on the brakelights and not take them off which sends a signal to the tranny computer to unlock the torque converter.

You might want to check your brake light switch, replace it or make sure you get all the play out of the linkage so the switch will always work properly.

Just push on the brake pedal and check your break lights to make sure they go off once you take your foot of the brake. The lights should always go out. Sometimes the switch won't go out if you just tap the brakes and if this happens the Torque Converter won't unlock. Sometimes the switch ends up flickering (going on and off) which is probably why you kept engaging and disengaging the overdrive. Since you use the brake pedal more in the city and you often don't go over the speed when the TC engages (~38mph) the problem may not be as noticable. Also any play in your brake linkage or a bad switch would only show the problem intermittently so troubleshooting can be a real pain.

A code scan won't tell you much either as when I scanned my dads E4OD all he got was Codes that pointed to a 1st and 2nd gear shift error as well as the VSS error all of which are just symptomes which won't tell you where the real problem lies.

Your problem could be ground related also but it sound more like a problem with the brake switch / linkage wear to me.

All I did on my dads truck was replace the plastic bushings on the master cylinder rod loop and replaced the brake switch.

A good check is to see if your brake lights stay on. Sometimes my dad would lock the truck and as he walked away he noticed the break light stayed on and would not go out till he stepped on the brakepedal once or twice.

Lastly, make sure you fix this problem soon as all that shifting is putting stress on your tranny and could cause it to burn up if you don't fix it.

Sebastian.

 

Hamberger I like your info.... so I have saved it for future use.....if that's OK.

 

Go ahead, I just recently found time to get back on the board and you seem to be a steady hand at this so feel free to use it. That was this site is all about I think.

Sebastian.

 

good info, i've had that happen on a 86 f-250 gasser before. my brake light switch works fine. the problem is it doesn't start doing it til i've been driving for a period of time say an hour and a half or so. i drove to the bank today which is a half hour drive (i'm out in the middle of nowhere) and back and it never acted up once. i've got to go to michigan wednesday to pick up a car i purchased and i'm worried it'll act up again while hauling.it seems to have gotten progressively worse, on longer trips. i talked to my transmission guru today,and he mentioned the back feed threw the wiring, a worn out tp sensor,an over heated tc clutch also. what a pain in the a*#!! i liked my 5spd. idi for towing anyhow. what to do??? pete

 

a scan , most likely cause is a bad fipl , the fipl is potentimeter and the circuit board does wear and usually at the same spot on the throttle that you normally drive at , a scan first to see if it has any fipl codes , as for the brake light circuit the pcm recieves voltage from the brake light switch so the only way a bad ground affects it is to have teh running lights on and with no ground at a tailamp assembly the running light circuit crosses over to the brake light circuit

 

I ended up changing a TC after towing a U-haul trailer that had crappy wiring!! Lights on bad grounds in the trailer- coverter locking and unlocking.

 

This one is one for the books, and in hindsight it makes a lot of sense. Thanks for sharing.

I will think about this every time I hook up a trailer from now on.

Sebastian.

 

When my head gasket was going bad and the overflow bottle was spewing out water, It would wet the tp sensor on the injection pump, causing the same problem. I would spray that sensor with some electric contact cleaner or something like that...can't hurt. Don't use carb cleaner!!

 

Cornbinder,

I am havign the EXACT same problem. It usaually only occurs when the enigine is warm and has been driven awhile. I personally am thinging about getting a new wiring setup from Baumann. If you get your figured out send me a pm and let me know what it was. I have been troubleshooting mine for a few months now.....

Thad