I have a 2006 uplander with the 3.5 engine. I notice that at 100kph (60mph) the torque converter is going in and out of lockup every few seconds (alternating between app 2000rpm and 2100rpm) Sometimes it will be as long as 5 seconds or so. If you push the van up to 110-115 kph, it seems to stay in lockup until you hit a slight hill. Is this normal, or is it the sign of a problem?

 

Mine does the same; although only when I'm the lone occupant. Never does it when there's more weight on board (people or stuff). My trans also has the occasional "slam" into first from a stop. There is a valve that can be replaced in the trans, there's a video on youtube but you have to open it up to do it. That said, it's been doing it for 135k miles and still going.

 

3.5 engine is a little underpowered for the weight of this vehicle. 2000rpm is too low to provide necessary torque and strong wind conditions and hills will force transmission to unlock the torque converter or even downshift. Doing it every few seconds though is not normal. It's not necessarily a transmission problem, could be engine loosing power due to worn spark plugs, old ignition cables, dirty injectors, dirty air filter, low fuel quality, faulty fuel mixture related sensor, etc.

 

How long have you owned the van?
How many miles on it?
Has the transmission been serviced?
Did this problem begin "all of a sudden" ?

 

Me too. I cut the tcc wire at the trans. Tan as I remember. No lockup but is comfortable. Do not know what it does to gas mileage. Probably 2 mpg or so.
Sonnax has a kit for the 4t65e to fix a worn slide valve that can be fixed in one day at a shop and 3 days at home. UGH UGH horrible work, the absolute worst, but can be done in car by removing trans side cover and lowering cradle, support engine etc etc. Drain fluid and lay in dripping fluid all day long.
My trans at 120 k is clean inside; new filter did not fixit Maybe somebodys snake iguana oil will help. I am not willing to fixit my self at my senior age. As they say in brooklyn FORGETABOUTIT.