Random Hard shifting

[phewop118]

my intrigue did a strange thing today-when i came out of a store and was pulling away, i noticed the 1-2 shift was harder than normal. i stopped and tried again, with about 1/5 throttle, and the shift was hard and really fast - it rattled the bags in the car. As i went out on the road, it did that in the 2-3 shift too, but not 3-4 or to ovedrive. it kept doing it until i shut it off to fill up the gas tank. once i restarted it and drove away, it was as smooth as always. I know the transmission passthru connector can cause this, but wouldnt it shift hard all the time if that was bad? any advice? thanks.

[canatto]

My 2000 GLS does that too. It's been more than 2 years since she first decided to do this. There is a TSB with GM about this issue with the 4T65E trannsmission in our cars, or almost all W-body cars. I don't have the details of the TSB now but the culprit of this hard up-shifting, according to the TSB, was due to a failing or failed pressure control solenoid which have caused the hydraulic control system in the tranny to lose proper fluid pressure regulation hence the computer has no choice but forcing the hydraulic control to constantly operate in the highest fluid pressure, in order not to screw-up the drivability. The remedy? Change the pressure control solenoid, $600+ job as I heard.

In my case, the hard shift has been mostly a slight lurch, though in a few occasions it bangs into the next gear. As far as I understand this is not causing extra wear to the tranny so I decided to live with it until it becomes really worse, which it never did so far.

[panzer dragoon]

hey, try that lube-guard tranny additive. I got mine at Napa for $11. It helps loosen up that solenoid valve and could save you some money.

You may want to change your tranny fluid/filter and drop the tranny pan and clean out all the sludge (fine silt) accumulated at the bottom of the tranny pan.