GMC Repair: 05 Yukon 4x4 SLT transmission no 3-4, yukon 4x4, service 4x4

Question
I was driving my 05 4x4 Yukon. Noticed the service 4x4 light come on a few times. While driving the next day noticed a jerk shift into 3rd. Next stop light same thing. Then would not shift into 3 or 4th. I was only about a mile from home so drove it back In 2nd. Right before I got home light came on saying "transmission hot" I pulled the stick fluid was full butt now has a burnt smell. Any ideas what could be wrong with the transmission?

Answer
This is one oversight I see more and more. I try to deter customer from going to "Jiffy Lube" type place that will only vacuum out the old fluid and fill it up. Often times to the wrong level. When transmission fluid gets burnt it loses the properties to effectively help the valve body and clutches work properly.

 You should change the fluid, filter and pan gasket every 15K miles or twice per year. Typically the kits cost around $20-$30. Do not use the cheap fluid. Your automatic transmission is nothing more than a hydraulic pump. I would add lucas conditioner as well. Check you transmission cooler for damage. Changing this could help or go the other way. I would strongly recommending doing this yourself. Just make sure you clean all the varnish from the pan, and the magnet too.