Weird Transmission Noise

This is my first Tacoma so try to bear with me on this one please. A few months ago i bought my first Tacoma, a 2011 TRD Offroad. Well its been working awesome up till now no complains. However i figured i'd take it out for some recreational offroading nothing to crazy. We'd been on the trails in the Blackhills (SD) for a few hours when i came to this cattle gate situated on a bit of a hill so i stop the truck to let the wife out to open it and when i let off the brake the truck rolled back a few feet made a weird clicking noise kinda hard to describe and started beeping at me. Since then no other issues driving to work etc i would just like to know what happened to i can avoid it in the future. Could someone explain if i may have damaged something letting it roll back or what the heck that was? Never happened in any other truck I've owned. Thanks for any incite.

 

This happens on my brothers truck right now he has a 07 dc tacoma and we took it to get checked out the upper control arm bolt was loose and also he has about 60000 miles and the main cause was his bushing were worn and needs new one. If I were you just go get it checked out by some one

 

Your truck most likely has the exact same limited slip/skid control my 08 4runner has. If your in 4 wheel drive and it rolls backwards it trys to stop it. Check your owners manual there's a section on it. That's why you heard the beeping. There's nothing wrong with it.

 

yes it is down hill assist///its normal.....