I have an 89 gmc sierra 4x4, the problem im experiencing is the transmission doesn't engage from park to reverse or drive, there is an abnormal noise beneath the cab when the engine starts up.

My 2005 Sierra 4x4 did the same thing while running down the interstate on vacation. Scared me to death, thought it was going to shift into 4 wheel drive @ 80 MPR. Had to take to shop and they found a censor bad and they replaced it. Don't know cost, because truck was still under warranty.

You need the factory manual to accomplish this plus special tools.

The GMC I had you stopped, put the gear selector in Neutral, selected 4x4, put the gear selector in reverse and backed up a little then moved it to drive. Same procedure to go back to 2 wheel drive.

It sounds like that is your problem as it needs to be properly adjusted as it is very sensitive when selecting gears, if not set properly your gears will not engage, let me know if you sorted,

Not safe to drive. Sun shell broke or stripped out. Does it have all 4 foward gears? If so you have a different problem. Still in trans though.

first check oil level,if oil level is ok change oil filter and oil get a trany flush hope this does it if not it is your tany

try going into reverse for 10 feet then go to drive for 10 feet that might help if not it is to the wiring to you 4x4 engage system (wires to your wheel hub)

I’m happy to assist further over the phone at https://www.6ya.com/expert/john_2c7bb9c157d0baa8

try reversing six to eight feet after shifting into 4WD. PLEASE RATE MY ANSWER.

GOOD MORN SNOWED 18 INCHES ENGAGED FOUR WHEEL DRIVE IN BOTH HIGH AND LOW, FRONT LEFT WHEEL NOT PULLING RIGHT FRONT DID PULL. RODE AROUND FOR A WHILE. WHILE PARKING THE TRUCK IN MY DRIVEWAY THE FRONT RIGHT STOPPED PULLING IM STUCK IN SNOW NOW. TEN MINUTES BEFORE RIGHT WHEEL STOPPED PULLING THE DFROSTER BLOWER MOTOR STOPPED BLOWING ANY IDEAS

switch to the auto 4 wheel drive in park. reverse truck and then put it in neutral and try to switch back to 2 high