I have a built 4l65 Trans with the Transgo HD 2 shift kit In a 2002 avalanche. When I let off the throttle to coast in forth gear what will cause the lockup to stay locked. I can tap the break and watch the lock up dis- engage on my scan tool but when I let off the breaks it goes right back into lock up during coast . I thought that when I let off the gas completely it should unlock right away to start coast. Ive tried to put my stock computer back in and it does the same thing. So I don't think it's in the tuning software. I've changed the TPS switch , speed sensor, and IAC on the throttle body. The throttle body is a bbk 80 mm. The rest of the truck has 4.10 gears and a yank 2600 stall. It's has a cable driven ( not electronic) TB. All the other gears and Trans works perfectly. It has a aftermarket cooler and I've watch on my dash gauge as well as with the scan tool to see the Trans is at no more that 150 degrees . What outside of programing forces will cause the lock up to not dis-engage?

 

its suppose to stay locked when coasting, it would be super annoying if every time you let off then gas it unlocked, then locked when you hit the gas again.

 

I really thought from a few I spoke to it s suppose to unlock then lock back when u re- engage gas

 

A 4L80E will do that, but all the 4L60E's will do that all except a very few applications.

 

Do u know what the exceptions are for a 4l60 because mine stays locked even with the stock tune

 

ITs suppose to. im sure you can get it tuned out if you want. Dunno why tho. its annoying as crap.

I cant remember which application mimiks a 4L80E setup.

 

The NNBS 4L60E's TCC unlocks when the throttle is released.

 

Mine does down until about 45 mph then it unlocks. I actually like it because it goes into decel fuel cut off so no gas is being used and it makes for some decent engine braking so I'm not wearing on my brakes as much.