I have a fairly hilly route that I take to work everyday. On the hill inclines, the truck will increase throttle to keep speed when the cruise is set (normal) and then pull the throttle out to coast down on the back side of the hill when it begins to decline to not exceed the set cruise speed. This is normal and expected with the cruise set. The problem is that, the torque converter will disengage/reengage in the valleys when the truck senses that the decline is over and throttle needs to be applied again. The cruise pulls the throttle completely out and the truck coasts down the hill. If I just keep my foot on the throttle going down the hill, the torque converter stays locked when the cruise gives more throttle to go up the next hill. These are not steep inclines, just hilly enough to coast and then go into the next hill where throttle needs to be applied quickly. Gets into this heavy throttle and then coast sequence.

Is this normal? Is this going to shorten the life of my TC? Is there anyway to reprogram the computer to limit throttle position to keep it from coasting down the hills and then reengaging the throttle so harshly?

1997 GMC Jimmy 4 door 122k miles

 

Can also be an engine performance problem (lack of power) or brakes dragging - causing throttle to increase too much and TC to kick out. But yes, a lot of this is normal. They went to carbon fiber friction material because there is always some slip (variable) in the TC in the later 4L60e with E3. Never completely locks up. I wouldn't sweat it unless the trans is getting hot.

 

Thanks. I have thought about getting a trans temp gauge as I know the 4L60E is common to get hot. It's not so much a power issue, I notice the TC lock in after the back side of the hill after the throttle has been pulled out and the the trottle gets engaged again. Same effect if you were to take you foot off the petal going down a flat road (50-60mph) and then reengage the throttle. The rmps jump a little before the TC grabs and settles down.