TQ Lockup

[Circle-D]

Sounds like it might be the tune. Get a scanner on it and see what the computer is commanding. If the computer is telling it to cycle, then you need a tune. If the computer says stay locked, but it is not. Then need to go into the trans to see what the problem is. Solenoid, valve worn or maybe even the converter.

Chris

[oleshifty]

My blazer does that. Locks/unlocks constantly going 45-55. REALLY annoying. I THINK mine is supposed to though.

[petey62782]

Most converters are programed to come on at 47 mph minimum so it drops below that it might disengage so it's either programing or maybe your lock up solenoid if it comes in to hard then it sounds like the PWM solenoid is either programed wrong or no good hope this helps

[graysilverado5.3]

I know for sure its not the converter. I guess i'll have to take my truck to my tuner and ask him to check it out, if nothings wrong with the tune, I assume its the solenoid thats bad then. Would I have to drop tranny to change out that solenoid? Thanks for the help!

[petey62782]

Most of the solenoids can be accessed from dropping the pan and there on the valve body but some like the TCC solenoid you have to drop part of the valve body because it's all one wire harness it's hard wired into no disconnect clip but most solenoids are plug in clips

[petey62782]

Something else to consider is the park neutral box on the side of the tranny it also tells the computer what gear you in and the black box shorts out alot or there rubber seal leaks water in and if that goes on a fritz it will give the wrong grea info to the computer and cause problems it also runs on the same ground as the PWM switch and if the voltage is wrong it will tell you converter to lock up differently

[aj06bolt12r]

They are supposed to do that with the stock tune. The pcm unlocks the torque converter when You let off the throttle a little to prevent what it perceives as un wanted engine braking to help with fuel economy. Mine does it alot around 50-60mph. Especially with the cruise on. I also just installed a 2800 stall and now it drives me crazy. I'm hoping it can be eliminated with efi liive. I installed my cam heads longtubes and injectors last weekend and should be getting a dyno tune this weekend. Ill let you know for sure if it can be tuned out.

[danger_ranger83]

Most of the solenoids can be accessed from dropping the pan and there on the valve body but some like the TCC solenoid you have to drop part of the valve body because it's all one wire harness it's hard wired into no disconnect clip but most solenoids are plug in clips

The TCC noid can be taken out without dropping the valve body. There is a solenoid that's right below it but all you need is to remove a clip and the solenoid can be taken out. If it's not tune related I'd check the filter on the TCC solenoid.

[farmtruc]

If it's the tune, lower the tcc unlock mph table for 4th gear, about 5 mph, it may be too close to the tcc lock mph value.
Any slight variation in the tps will lock and unlock the converter; if these values are too close.
the 80e does unlock when tps is around 0%, so the truck will coast freely, that is normal.

also, something else you can try, increase the min pressure for the tcc table, just multiply it by 2 for starters.

good luck,