Took the blazer to Delaware over the weekend. It was about a 3 hour drive, had the AC on, driving at night, no problems until driving for maybe a little over an hour and a half.


I noticed it when I came to the first toll booth. I stopped and handed the person money to get through, and as I started to move my car jolted from 1st into 2nd (almost as if you had a bad motor mount). It was fine through all the other gears and fine when I was driving, but as soon as I stopped again it did it all over.

When I finally got to the destination, I let it cool down, and took it for another drive and it didn't do it. On the way home after the weekend it started doing it again after an hour of driving. What could this be? It deffinitely needs a tranny flush. Could that be it?


Also, I said I used the AC the whole way to delaware with no problems, but on the way home I was using the AC since it was hitting 97 degrees out and my temp gauge started rising. I didn't think nothing of it until it just barely hit the red (thought it was because it was so hot out) while I was at a red light, and I dropped the windows and shut off the AC and it went down back to normal after a little more driving. Thermostat?

 

It's possible the PCM modified the shift point due to high fluid temperature. This might be due to a bad thermostat, or a faulty fan clutch. Buy Imperial Fan Clutch - Severe Duty 215158 at Advance Auto Parts____

The transmission cooler is in the radiator, and it's a pretty cheesy cooler. Totally bypassing it and installing an external transmission cooler will extend the life of the trans: Buy Imperial Maxi-KoolŽ XL Transmission Oil Cooler 243012 at Advance Auto Parts____ Couple of hours work makes a big difference in cooling. The grille has to come out to install the cooler, but that's only a 3 minute job.

It's also possible that a spool valve in the transmission valve body was sticking when hot, (seems like there was a TSB on this).

Avoid the trans flush, instead, drop the pan and replace the fluid, gasket & filter.

 

Have you checked the tranny fluid and looked for any leaks of either tranny fluid or coolant? Could be the water pump going out, but I would check the coolant. Could just need a new t-stat and a good flush of the cooling system.

 

When I experienced this same problem it turned out to be a shift solonoid issue. My hard shifts were intermittant as well.Had a shop swap it out (accessable by just dropping the pan) and all was fine.