78 k20 np203 and concerns about noises

[Bthomas78k20]

So, im a newbie that bought a 78 k20.
Knowing little about the 4x4, i bought it and drove it an hour home as is. (55-60 mph on freeway) it ran fine and i didnt have concerns, but after reading, it was in L the whole way and read i should be driving in H. So when i took it over to a shop for the lift install, i made sure it was in H. (It was obvously not in N and was not in H lock bc the light wasnt on on the dash)

My concern is that it drove like what sounded like a desiel or loud tapping that faded out as i excelerated but got loud when going into 2nd then faded out again.

Its an automatic

Im concerned about damage, the trans, the front driveshaft or if something else needs attention??

When i get it back what can i check or do to trouble shoot the issue??
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