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Folks here were a great help when I needed to get my transmission rebuilt on my 1997 F350 diesel 4wd pickup. After the rebuild the transmission worked noticeably better and felt stronger when pulling my trailer. I had the usual rebuild plus had a billet converter installed as well as stage 3 friction clutches from Raybestos.
After 6 months of driving without an issue I have noticed that my torque converter has started to occasionally and temporarily unlock while I am on the highway. It never occurs under heavy throttle, only under a light throttle. It sometime occurs when I give it a very little amount of throttle or when I very slightly ease off on the throttle. When it happens the TC usually unlocks for 3-5 seconds then locks up again. When this occurs the situation does not even come close to calling for a gear shift, yet the torque converter unlocks. One interesting thing I have noticed is that on a section of road I travel on frequently the TC temporarily unlocks 95% of the time I pass through that section. I have checked the ground connection and I do not have LED tail lights.
The transmission is under warranty so I took it to the shop and they checked the codes and none came up. They also took it for a test drive (I rode along) and the TC never acted up (or course). The mechanic said that since there is no codes showing up the transmission is doing what it is told to do.
I am trying to figure out what to do next. Do you of you who have experienced this before have any words of advice for me?
With those truck's you'll probably need a scanner that can read in real time to make sure your ECM isn't commanding an unlock state when it shouldn't be.With our IDI trucks (the 7.3l before the power stroke) we could tap into and watch our ECM by probing a few wires and running a test light.
Something else to check if you want that's just as simple and probably more likely anyway,since it seems to locking and unlocking most of the time when it should be,is to inspect your solenoid pack plug.The plug on the passenger side.Make sure it's clean and fully seated.The ECM commands a ground to the converter lockup and if it's a bad connection and ground breaks,the solenoid wont be grounded and the converter unlocks until it's gets a signal again.You ever get a bad ground on a light somewhere,where it flickers? Same thing could be happening here with the line to the solenoids.
The mechanic thought it could be a bad ground and had me check the battery terminals and the connections to the block and they are all good. I know this isn't quite what you are talking about but with a bad ground somewhere it seems like the unlocking/locking of the TC would be completely random. Because the TC unlocks/locks at the same location on the same road every time I pass through it seems like it would be something that is sending a false signal rather than a bad ground.
I still find it interesting that the unlocking of the torque converter is not completely random. As I mentioned above there is a section of road I drive about once a week (a slight downhill curve to a slight uphill section all at 50 mph) and the TC unlocks for at least 5 seconds (after that I move the throttle pedal to try to get it to lock up) 90% of the time I go through. The speed, slopes, etc. no where near requires anything close to a gear change.
After reading his reply I went and checked my truck and found my third brake light was not working. I checked the bulb and found it to be bad. I replaced the bulb and monitored the transmission over the next week and not once did my torque converter unlock when it wasn't supposed to.
Thank you Mark for your contributions to this forum. You are a huge asset! You saved me a ton of time and probably a ton of money trying to hunt down the source of my problem.
09-12-2018, 08:35 AM
