Gear noise in 4 low

Just bought a 2015 sr5 4x4 (first 4wd vehicle). I took it out on some dirt roads to try out the 4wd system. Switching to 4H and back to 2H worked great. There was a barely perceptible clunk and the 4x4 light went solid or dissapeared. There was no additional drive train noise in either mode. 4L was a different story. Stopped the vehicle, neutral, flipped the switch. It wouldn't go into gear. I had to put it back in drive, scooch forward, and try again. Everything worked the second time. One thing I noticed very quickly was the amount of gear whine at any speed (didn't take it over 10). It sounded like driving in reverse.

Is this behavior normal? I know reverse is noisy due to the spur (vs helical) gears. Is it the same thing in 4 low?

 

Normal

 

100 % normal, probably due to the straight cut gears that are used in 4 low. No harm in running her up past 10mph.... i have done a few spirited stints on fire roads in 4 low close to rev limit in top gear.

 

Yep, normal.

You're going to get the clunk most times if you engage 4 hi while stopped. switching between 2 hi and 4 hi is best done while rolling, without too much pressure on the gears (coasting - foot off brake and accelerator). 4 lo will engage easiest in neutral with your foot on the brake pedal. Practice going through all of the drive modes. These trucks can be finicky and if you don't have a few tricks up your sleeve, you won't be able to engage the drive mode you need when you need it. Being proactive is good - sometimes when you're already stuck the truck won't want to go into 4 or 4 lo.

The gear noise is just a whine from the low gear ratio.

 

It's normal. I use 4lo a lot when mall crawling for soccer moms. I helps to climb the snow piles on Black Friday when parking is at a premium. The whine and hood scoop drive the ladies crazy!!!
All kidding aside, yes it is normal. I only seem to get to use 4 lo when I exercise the 4wd. I try to use it at least 5-6 times in the summer to keep things working. This stuff always feels like use it or lose it.