Contour Enthusiasts Group Archives Forums Modifications Transaxle Transmission trouble, after driving for 45 minutes

Well, after replacing the original valve body with a rebuilt VB with all new Sonnax valves about 2 weeks ago, it happened again yesterday. I was driving for about an hour at about 65 MPH, I get into town at a stop light, and the car shifts hard again, this time it did not set off any CEL. And after it did this about 3 times, I pulled off the road, shut off the car, then restarted it and it shifted fine after that. So why would this work? Shutting the car off for about 10 seconds, then staring it again. Hard shift is gone.

Any ideas?

P.S.
I did not install a cooler when I had the rebuilt VB installed.

Thanks.