2000 4l60 Luggs in lockup.
 

Hey guys, can someone point me in a direction to fix this problem.
I've searched and have not found anything.

Well here's the deal. My truck will stay locked up in OD all the way down to around 30mph.
On long hills running around 30 to 40 the engine seems to be lugging. If I tap the brake , it unlocks and the engine seems much happier.
If I try to accelerate while slowly pushing the gas pedal the converter never unlocks, only till I'm what I think is half throttle the trans jumps back to third.

Other than that , I'm having no drivabilty problems, no CEL.
The truck does have over size tires, the odometer is off by 10% , check with a gps.

Any help is appreciated.

Thanks

This isn't helping the problem.

Fix the speedo reading.

Lockup at an actual 40mph and higher isn't typically a drivability issue.
Your tune isn't correct, so it's not going to have good lockup timing for best drivability.

What's the best way to fix the speedo?
Get a tune from someone like black bear?

The thing I don't understand is why I'm never able to get it to unlock when applying throttle.

Thanks for the help

The tune determines how much throttle it takes at various speeds to unlock the converter.
As mentioned first step is to get the speedometer corrected.
The tuner can then change the lock and unlock parameters.

Your engine is lugging because the RPM is too low.
Some of us with extreme performance cams cannot lockup under 2000 RPM or about 50 mph, or we have severe lugging.