I have a 97 yukon 4x4 and it did something strange twice. When I was driving it started acting like the transmission was slipping. It would switch gears real hard into first and second. After I turned the ignition off it ran great for a few days then it did it again and I turned it off and it was fine that was 3 days ago. Help?

Is your Check Engine Light on? It would be a good idea to check for any stored codes. Code P1870 is pretty common on the 4L60E.

When the tranny shifts hard, it has detected a problem and raises the line pressure (this is sometimes called "limp" mode).

First thing is to check for codes.

//2000CAYukon

Had the exact thing happen on my "99" three weeks ago. I have a "16 bolt pan" on my transmission, some have a 17 bolt FYI. Took the car to the dealer and they quoted $1,000.00 to fix it with no warrenty, $2,700.00 with one. I replaced the 3 selonoid valves the one that controls the tork converter and (1) that control the 1st to second and (1) the 3rd to forth shift. Total cost $60.00 and 1 1/2 hrs time. There all under the pan and easy to do. Drove about 500mi since (200 towing). No problem.

Good Luck.

Thanks both of you for your suggestions they have helped alot. I had no idea what could have been the problem hope these work.