Rear Differntial Lock
 

I recently got a used 2008 FJ Cruiser and am new to the whole off roading scene. Anyways, a couple days ago, I was off roading and put my FJ in 4 HI and turned the differential lock on and started mudding around. I exceeded 5mph, which I read today, is not good :/. Shame on me for not reading the owners manual first! Also, I've heard that you are not to engage it in any setting other than 4LO. Is it possible that I caused some damage in doing that or is it fine? I don't or didn't experience any problems while doing so, so I'm assuming everything is fine. Feedback is definitely appreciated! Thank you all and have a most blessed day!

Is it possible your confusing the elocker with the center diff lock and 4lo "when to engage" processes?

Doubtful that you did any damage, have you noticed any new sounds or issues since you did this? I am also curious if you mean the center differential vs the rear locking differential.