4x4 Problems

Hi, I have a 2002 LS EXCab 4x4 45k miles
2 months ago i engaged 4hi and heard a loud noise, not sure if noise was
in the cab or under truck. 2hi light was still on while hearing noise, i pushed 4hi button again but nothing happened(still making noise). I slowed down to under 30mph and 4hi engaged and the noise stopped.
( hard to tell what kind of noise it was )

A month later had trouble engaging 4lo and 4hi while stopped and in neutral. i got 4lo in then got it in 4hi, then it would not come out of 4hi.
I put truck in neutral and got it back into 2hi but then only had 2hi and 4lo.(Nothing happening when pushing 4hi button)

Had dealer look at truck they reset tccm and said if it happens again i need to replace tccm. It happened again 2 weeks ago and i reset myself.
I have 4hi and 4lo but if seems to drop in hard with a thunk.
The lights don't flash when selecting a new range, it just seems to drop in all at once.
Should lights flash while selecting new range?
Is this a tccm problem or a encoder problem?

Hope someone can lead me in right direction. Thanks

Hope you aren't switching to 4hi while accelerating.

You really shouldn't be shifting into 4x4 above 30 as it is. I know the book may say otherwise but the high speeds are hard on the gears, the loud clunk you heard.

The lights don't flash when selecting a new range, it just seems to drop in all at once.
Should lights flash while selecting new range?
Is this a tccm problem or a encoder problem?

Hope someone can lead me in right direction. Thanks

As far as the lights flashing, mine flashed 2 or 3 times when going from 2hi to 4hi when I first got the truck. At 27k, the front diff went and after they replaced it, my buttons would not flash, just goes straight in. I asked the dealer about it and he said some engage faster than others and it is normal.