hard shift 1-2

I have A 97 BLAZER with a hard shift from 1st to 2nd after driving on the highway for a period of time, my understanding is its a valve in the tcc. that sences slippage in the a/t causing the trans to have higher fluid pressure. My question is if you are driving in 3rd rather that OD is the tcc taken out of the equasion?
thanks for any help
mike

Mike,
I believe your answer is yes. When I bought my 2000 a few months ago, it had a bad Shift Solenoid "A" (DTC P0753) which caused a second gear start and no 3-4 shift. Replacing the solenoid corrected the shift problem but a few weeks later it developed the same problem you describe but its intermittent. When it starts the rough 1-2 shift, the SES light comes on, scan shows a DTC P1870 which is the TCC slip condition and also DTC P0753. Previous posts described changing the TCC solenoid with successful results. The solenoid runs about $60. Seems this is a common problem on 4L60E transmissions.

There is a TSB out that says the problem(TCC slippage) can be caused by a worn passage in the valve body. Transgo, Superior Transmission and Sonnax all make correction kits.

Umm, if the TCC was the problem, it would do it all the time, not just after being on the highwy.

Go get your tranny flashed and the fluid and filter changed.

Sounds like your tranny might be overheating.

I had the exact same problem with my tranny only it seemed to be more intermittent then "after 30 minutes on the freeway" but any way I flushed the tranny and it resolved the issue 15,000 miles later shifting is still fine.