I'm pretty sure the brake lights are working proberly. Another thing is if I shift it into 3rd the rmp will raise about 200-300rpm then if I shift it back into drive it will go back down to 2krpm at 65mph like it should be when the overdrive is in.

 

That sounds more like it is shifting down to 3rd gear, but maintaining torque converter lockup. This could be caused by a problem with the 1-2 shift solenoid which is off in 3rd and on in 4th. If there is something causing this to drop out when you are off the throttle, it would cause a drop to 3rd gear.

 

I see. I'm pretty mechanicly inclind but how do I go into changing the soleniods myself?

 

It may not be a problem with the solenoid per say, but the circuit that controls it. You really won't know until you get it properly diagnosed. That is something that is VERY difficult to do without access to the vehicle (i.e. from across the internet).

 

Good info I have been having this happen to me too. Any time between 40-60 MPH I can see the RPMs bounce between 1.5k-2k. I will try to get a video or somthing of this happening.

 

Unplug your 4wheel drive module (passenger side kick plate) bet the problem goes away. Let me know what happens.
Grillzy

 

Ok so here is a video I took the other day of me driving to work. It's kinda long but what I am talking about happens at around 23 seconds into the video. I was on a pretty level road with cruise control set at 50 mph.

http://i10.photobucket.com/albums/a1...ent=blazer.flv

 

Forget my last post - not what I was thinking
Grillzy

 

blazer073, that little bit of change could just be the PCM altering the TCC lockup for the conditions. 50mph is a 'tweener' speed where the TCC first starts to lock up when cruising, but may unlock given calculated engine load. Does it do this while you are running at say 55mph or 60mph on smooth level ground?

 

Mine will do it at any speed even up to 90mph