Hey all,

I have a 2000 Blazer 4x4 with 159k miles.

It runs very well, but if I drive it on the highway for about a half hour or at speeds over 60mph for a half hour or so the transmission overheats.

The symptoms include the RPM going up to around 3,000 while driving (normally at 60-65 it's around 1,900 - 2,000). If I slow down/get off the highway it will shift rough from first to second. If I stop and let it cool down for about 5 minutes, it will shift fine and act just fine.

Driving in the city I have no problems at all.

The fluid looks OK to me when I check it on the dipstick and it is not low. I have added some lucas to it, but that didn't fix the issue. Having a hard time finding a shop to flush it as it is over 100k miles.

Has anyone else experienced this issue? How did you fix it?

I am thinking I need to do a flush myself or replace the cooler lines. Any help is appreciated! Thanks