My 1988 K1500 four wheel drive has grinding sound, 2wd works just fine, only when I engage the four wheel drive does it make grinding sounds, and the left front turns roughly and irregulary. I think I shredded a hub?

Very bad news, stop at aamco

It sounds like you have different size tires on the front than on the back causing the t-case to bind up. If not, your having an engagement/disengagement issue in the t-case or the shift actuator for the t-case

There is an acuator in the front diff the are common to quite in late 80 to early 90 Chevrolet's / GMC

Could be bad or sticking hubs, wheel bearings or u joints. When you said it went away when 4wd engages tells me that your right its partially engaged. Had the same issue with my 95 SUV 2yrs ago and had to replace the locking hub assembly. It had the electronic auto hubs. They were shot and starting to fall apart.

you probably need to put a new actuator in it

put the truck into neutral and roll it back 4 low is a semi manual engaged drive just putting it back into 2wd wont work

w9fro..In1995, and other model years, the actuator used to engage the transfer case into four wheel drive is oil filled with a heating element.
When you select four wheel drive the element heats up, the oil expands and engages the transfer case. Unfortunately if the actuator fails, the truck remains in four wheel drive. GM has an improved actuator so the problem does not repeat.
As always, check the basics, power, grounds and switch at floor select before replacing the actuator.
Also, if the truck is truly stuck in four wheel drive, you can tell by turning the truck in a tight circle. If the front end wants to "bunny hop" it is definitely engaged.
Best of luck, let me know.
Regards,

ASE mechanic here:
check the king pins in the front end and the u joints for any kind of play. sounds like front end play while four wheel drive is engaged and stills is affected for a while when two wheel drive is activated. this year truck most definitely has a manual four wheel linkage that could be the problem too. try lubing up any moving linkage and i would shift it in neutral. keep me posted

Hello;
Sounds like yoou have a short either in the switch pod or in the 4wd electrics. Check for pinched wires or bare wires grounding out at the front axle and at the transfer case.
Thanks;
Rich
RPM Northwest

sounds the wheel senser reading something not working properly