We have a '96 Olds 88 (3.8L, transmission type = 4T60E). After the car is driven - about 200 miles and you're driving at highway speeds - and you give a little gas to pass, the car starts jerking. But if you shift from 'D' to '3' it runs smooth as SILK. In overdrive on level ground, it's OK.<P>The dealership thinks it needs an updated GM valve body. <P>Anyone have any clues about this? Is this something that's easy to do? I'm picturing dropping the pan and reaching up to a couple screws for replacement of this...

First I have never had this problem so I cant advise on knowledge.Maybe you could talk to a transmission shop guy. You know get another opinion. Get many opinions. These trannys and the V6 FWD combo have been around for awhile so I dont understand why a 96 would need a update. Maybe a fluid change and filter is in order.

Check the TVI cable the goes from the throttle body to the transmission to make sure it's positioned right, you might also check the electrical plug for the lockup torque converter, might even unplug it to see if the problem goes away, mine has been unplugged 9 months now because the converter does not always unlock.