5R55E Converter Lockup Issues

[Guggenheim99]

02 5R55E 4X4, having a couple of transmission issues. Long post but want to put all info in here. First noticed this past Wednesday. I will be driving along either in 4th or 5th with the converter locked up cruising, and it would randomly just unlock the converter, but stay in the same gear. Not slip, shudder, like you just turned a switch and it unlocks. Then after a little bit, would lock up again. Then anywhere from 1 second to 15 seconds later, it would do the same thing again. Rinse and repeat. During this I would not change throttle input at all, so that isn't causing it to unlock randomly. Sometimes it would operate as designed for miles, then act up for miles. I also noticed it would shift way too early and harder then usual during these events if I happened to come to a stop (I've owned this truck for 8 years so I know how and when it's supposed to shift based on how much throttle I am giving it, and it's definitely not right) I let it sit overnight, then drove it a combined 100 miles with not a single issue at all the next day. Today rolls around, I hop in and drive 15 minutes into a 1hr ride, and it starts acting up again. Same exact symptoms above. Then about 10 minutes later, it went away and worked fine for about another 15 minutes. Then the last 20 minutes acted up again, and also a few times it hesitated taking off momentarily in 1st. Let it sit for a few hours at my destination, debated having it towed back home. Drove it back anyway, drove fine for 15 minutes, acted up again for 5 minutes, then drove perfectly the rest of the ride home. Does not seem temp related because it has been at the same temperature both when it was operating fine, and acting up. Got home and checked fluid level, to full mark and clean/not burnt. No codes stored (checked with ForScan) Kind of confused. It seems electrical related because the concern seems to either go away or is delayed for a while after letting the truck go to sleep. Maybe I am wrong. Other then a leaking servo cover and rotted out pan early in my ownership of the truck, have had 0 issues at all over the years. Any ideas? If you need more info let me know. Thanks

 

[franklin2]

I was betting you had some codes. Sounds like when the engine speed does not match the calculated output speed of the transmission, so the computer thinks the trans is slipping and drops it out of lockup and puts it in a limp mode with high internal trans pressure. But you would have a code stored for that.

Never used Forscan. Is there another place in there that a code may be hiding?

 

[Curious Hound]

Next time it happens, use your toes to lift the brake pedal completely as high as it will go. See if that makes a difference. I've had to add a bungee cord to the brake pedal in my superduty to make the lockup work properly.

 

[Guggenheim99]

I did some research in the shop manual under transmission description and operation and it gives you some of the inputs that go into TCC lockup, mainly brake pedal position, throttle position, MAF, IAT. I have had all these inputs pulled up on the scan tool and driving attempting to find an abnormality in one of them, but unfortunately it's been over a week since the concern happened last and has been functioning as designed since then lol. I'll continue to monitor and if I ever find the resolution I will update