Toyota FJ Cruiser Forum

I just bought a new FJ last week and I'm trying to learn about the 4wd features. I just read another thread on the A-Trac and have a new follow up question.

I understand the A-Trac feature and how it is used. (Thanks to this forum and You Tube videos). My question is as follows:

My FJ has both A-Trac option and Rear Diff Lock option. What is the difference? My best guess is that the A-Trac applies breaking pressure to a spinning wheel whereas the Rear Diff Lock essentially locks the differential so both wheels spin together. As I am guessing, the RDL would be helpful in sand where you will almost always have wheel slippage on all 4 wheels - compared to the A-Trac that applies break pressure to a wheel that is off the ground when going over a rocky ditch and applies the energy to another wheel that has good traction, for example.

Am I correct? If not, can someone explain?

Thanks.

Charlie