I'm not sure if your model has a way to change the P-Setting (controls the auger cycle) but you can read about it here:
http://tipsforbbq.com/Definition/Traeger-P-Setting
We have the smaller one from Costco and it does tend to have around 60-70 C swings, and a lot more if you tend to open the lid. For example, if we set it to 225, it will go up to about 260 and down to around 190. One thing we learned is to minimize the lid being opened, and not to check the meat inside too much.