Can driving a 1999 gmc jimmy with 4wd in 4low range over 55 mph on the highway damage the engine

okay not one word what the tires of the car are rolling on
dirt or ice. or raw hard pavement
nor the exact control settings are set.

the jeeps have many 4wd options new, (I have 2020 here)and I have full factory service manuals on all GC. made. gen 1,2,3.
most have Three levels of 4WD.
2005 to 2010 same as mine.
came with 2 choices new of transfer cases not told by you at all.
lets do both and answer what THEY DO and DO NOT DO.
nv140
The NV140 Quadra-Trac I (no part time modes) and uses brakes top stop tire slip. (smart)
is a single-speed transfer case and it is used in the Quadra- Trac I Full-Time 4-Wheel Drive System. It
provides full-time 4-wheel drive. The transfer case operates with an open center differential dividing engine torque
nearly evenly with 48 percent of engine torque to the front axle and 52 percent of engine torque to the rear axle. SO NOT YOURS

yours is this, read the users guide on 4wd low limits.
nv 245 has ,Quadra-TracT II and Quadra-DriveT II systems.
4wd low and lockups up the center differential.
and is not for pavement. (lacking ICE covering)
4WD Low, which multiplies engine torque 2.72
times and locks the clutch pack for maximum traction at all times
key word LOCKS. this for offroad and or ice only.
not for pavement.
do not use Low. or any kind of part time 4 wd modes, on pavement free if ice. (no matter the car owned)
or you windup the axles and steering fights the driver.
and is very dangerous to do and makes ABS go nuts. etc.
read page 240 in your users guide.
240
The Quadra-Trac IItransfer
case provides three mode positions - four wheel drive
high range, neutral, and four wheel drive low range.
and
The 4 LOW position is intended for loose, slippery
road surfaces only. Driving in the 4 LOW position on dry
hard surfaced roads may cause increased tire wear and
damage to driveline components.>. bingo the D word,.


if stuck in 4low
move one or more tire to ice or dirt.
shift out of 4low to 4hi at dead crawl speed,the slower the better
not grinding teeth to deathh wins.

4low is for dirt
or stuck in a snow drift.
otherwise stay out of 4low

https://www.carmanual.org/jeep-owners-manuals/2005-jeep-grand-cherokee-owners-manual-2983/

bad u-joint would be the first thing to look for if the sound is coming from just one side. when you engage the front axle, you put it under load and it shuts up.

Check this information about your 1999 GMC Truck Jimmy 4WD 4.3L SFI 6cyl :

Engine Oil Type/Weight/Capacity
683690
Application:
Use in all temperature ranges
Note : Valvoline Premium Conventional 5W-30 Motor Oil 5+ Jug


98HC54
Application:
Use in all temperature ranges
Note : Mobil 1 EP 5W-30 - Extended Performance Synthetic


220013721
Application:
Use in all temperature ranges
Note : Chevron Supreme 5W-30 Motor Oil


550022689
Application:
Use in all temperature ranges
Note : Pennzoil Platinum Full Synthetic 5W-30



Hope this helps (remember to rating and leave a testimonial about this free answer).

1. • 1 Start your Dodge truck's engine.
     
   • 2 Turn the electronic transfer case from "2WD" to "4WD Lock" to engage the high range 4WD, if the dodge truck is equipped with an electronic transfer case; otherwise, shift the transfer case lever from "2H" to "4H." The electronic transfer case is located on the instrument panel and is marked with "2WD," "4WD Lock" and 4WD Low." The lever-equipped transfer case is located to the right of your leg and is marked with "2H," "4H" and "4L."
     
   • 3 Shift the transmission into "Neutral" while the vehicle is either stopped or rolling at 2 to 3 mph to begin engaging in the low range 4WD. Turn the electronic transfer case to "4WD Low," if the Dodge truck is equipped with an electronic transfer case; otherwise, shift the transfer case lever from "2H" or "4H" to "4L."
     
   Tips & Warnings
   • Indicator lights will come on and alert you that your vehicle is in either the high or low range of 4WD.
     
   • Do not engage in the low range of 4WD drive if the transmission is in gear; you must shift to "Neutral" first.
     
   • Many Dodge trucks allow you to shift from 2-wheel drive to the high range of 4WD at up to 55 mph--consult your truck's manual to ensure that this is possible. Do not exceed 55 mph while engaged in the high range of 4WD. Do not exceed 25 mph while engaged in the low range of 4WD.
     
   • Do not engage in 4WD unless you are on slipper or rocky roads.
     

i know u dont want to hear it but it needs a heater core /when at high way speeds u get enough flow trew the core

normal driving you want 2 wheel drive, snowy, slippery conditions 4wd part time up to 40 mph

look for a vac leak or loose wires on the trans its self

seems high to me. summer thermostats open at 185 , winter thermostats open at 195. At highway speeds , there should be more than enough air flow through the radiator to keep engine in the normal range. Your radiator might be pluged up and cooling poorly , but I suspect your temp guage might be inacurate.

get a scanner check code sound like vechicle speed sensor.

Most likely you snapped the 4WD chain in the transfer case. Put it in 4WD go in reverse with the wheel turned if the vehicle does this smoothly than your 4WD is not engaged.