Hard Shifts

I am sure this has been posted before. I have a 97 Sierra with a 4L60E that is having hard shifts from 1st to 2nd only after running on the express way. Any suggestions on a fix or any links to additional info would be appreciated.

Hi.
My 2004 shifts from 1-2 hard.No codes or check engine light come on.
Dealer finds nothing wrong ,although they do feel it on a test drive.
They will try to reprogram the computer.
Mind you this is happening at every 1-2 shift from day 1. 2 months and 2100 miles.Customer service was no help so a zone rep is now involved.
Good luck and I'll try to keep you informed.
Bill

I had the same problem with my 97 silverado. Dealership said there is a connector that gets corroded and sends the transmission into default mode. Mine fixed itself one day when I took it offroad and got it really stuck. Haven't had a problem with it since... Go figure!

Harsh shifts can be a result of the PCM detecting slippage in overdrive while the torque converter is locked. A pending(no SES) P1870 code may be stored. A possible cause is a worn valve body passage that the TCC apply valve occupies. There are kits available from Sonnax, Superior Transmission, and possibly Transgo to fix the valve body by boring the passage out and installing a larger apply valve.

I had the same problem on my 97 Serria. How many miles do you have on it?? Mine is over 100,000 so I did a trans flush, and it is much better now. :) I would try this first, especially if you have high miles.