2010 Silverado 1500

I suspect the engine fans are not turning on when they should.

Reason:

When stuck in traffic, the truck becomes sluggish and jolty. It reminds me of when my 2005 Malibu is accidentally put into low gear instead of drive; you can feel the transmission isn't working right/is running hot.

When stuck in traffic or idling, the truck engine stays at an average temperature of 100-105 deg C (good). However, the transmission temperature rises to 90-93 deg C (bad, I think); whereas the normal highway tranny temp is 47 deg C.

Idling:

When should the engine fans turn on? Would they cool the transmission? For example, should the fans turn on when the transmission is above n degrees? When Idling, I've only noticed the fans come on occasionally, and only for a few seconds, only cooling the transmission a couple of degrees (not enough).

For what it's worth, I noticed there is a smaller radiator in front of the main engine rad. I suspect the smaller rad is meant to cool the transmission.

I am a novice.