I have a 99 626, When I got the car from someone it would drive for about a 1/4 mile then rev up and not engage gears. I would pull over and turn off the car and let it sit for 30 seconds or so and start it back up and it would go again. I did this every 1/4 mile till I got home. First thing I did was change out the fluid to see if anything would change,,, it didn't. someone at work told me that they think its the valve body. I found a used one and put it in. It seemed to fix the problem, The car drove great,,, took it on a good long freeway drive (about 60 miles) got it close to home and it started acting up again. Wondering if the fluid is getting to hot? After letting the car sit for a few days I drove it around the block a few times, seemed good, double checked the fluid and its at the proper level. went to move it after driving it and it rev'd again... Turned it off,,, waited 30 secs turned it back on and it moves again. Dont know whats wrong with it other than it being a crappy tranny.