1990 k-1500 put vehicle in 4-lo or 4-hi it makes a clunking noise like something did not engage. sounds like it is from the front end other times from the rear.4-wheel drive works,just the noise.

Some vehicles have a actuator in the transfer case that the lever pushes against to engage 4x4.

There are actuators on the front axle and the transfer case, check them both.

sounds like you may need the encoder motor

the encoder motor on those style transfer cases are notorious for failing and that sounds like the beginning of the end for the one you have.

I have a 96 ford explorer that has a clunking sound when I pull out slowly . If I engage 4 wheel drive the clunking stops. I have replace the ball joints and right front axil and ground the breaks. Can anyone give me a suggestion. Sounds as if something is binding.

the auto 4 wheel does the same as part time in jeeps, it engages only when the vehicle loses traction. when auto 4 wheel is on the truck isn't fully in 4 wheel drive. my 02 sierra makes the clunk noise too but it does engage. try checking your fluids, i know its way pass the time for me to change mine out.

Check the drive shaf

Start by checking the axle half shaft u joints and then the drive line u joints for worn or loose end caps. Also if you have a constant velocity joint on the front drive line make sure the centering ball and socket are not worn. Most people never grease this item and by the time you figure it out it's too late.

your doing it right but your accuater is bad 59.00 auto zone easy install

Just to clarify, the "transmission" is not stuck in 4-Lo. It is the "transfer case" that is attached to the transmission that actually engages the 4-Hi and 4-Lo modes. To properly shift your vehicle into 4-Lo, you know that you have to shift the transmission into neutral and slow down to less than 5 mph. Once your vehicle slows down to this range, your can switch your transfer case into 4-Lo mode. Due to the inner workings of the transfer case, the actual shift into 4-Lo may take a few seconds to complete. This is normal and does not signify that there is an issue. All transfer cases that have 4-Lo mode will act this way regardless of the make or model. To make a long story short, to shift out of 4-Lo you must follow the same steps that you took to shift into 4-Lo, just in reverse order. Switch the transfer case to 4-Lo mode if it isn't already there. Slow down to less than 5 mph (your vehicle must be moving, though). Then, shift your car into 4-Hi or 2WD. Give your vehicle several seconds to complete the shift. The transfer case indicator light will flash until it is complete. When it does complete the shift into the new gear mode, you will most likely hear a "clunk" (the range sleeve inside the transfer case disengages from its mating spline) from under your car. Again, any transfer case with 4-Lo (regardless of make or model) will exhibit this same noise. This should help you get out of 4-Lo. It is good practice to shift your car into and out of 4-Lo at least a few times each year to keep all of the splines free of corrosion and build-up. Based on the age of your vehicle, your transfer case may also need a complete flush and some new transmission fluid. Hope this helps.