sometimes my truck idles really good at 750 to 800 rpm's and then sometimes it will idle way low at 550 to 600 rpm's and it will die when i put it in gear (automatic trans.). Weather is NOT a factor. does it in the cold and when its warm sometimes.

 

Sounds to me like your typical idle adjustment..

Assuming that this truck is an auto.....Now have the governer springs been messed with? If not then not to worry. I would bump up the idle to round about 950 or so, turn on the AC and put the truck in gear, it should be round 750 or so that way, so then u know its correct... Also make sure u tighten the bottom adjustment nut on the idle screw really well too, it will save u alot of hassle in the long run...

Rick

 

Check the two tiny bolts that hold the linkage to the idle adjustment screw. They have a tendency to work loose, sounds like in your case that one may have fallen out entirely. In the picture below the part is missing but the two holes the bolts go in are shown on the lever to the left of the low idle adjustment screw.



Idle adjustment instructions here http://dodgeram.org/tech/dsl/adjustm...d_Gen-Idle.htm

 

the governer springs have NOT been messed with as far as i know.