I recently test drove a 1998 Chev Silverado 4wd. When I came to a stop, shifted into neutral and pressed the 4 wheel low range button quite a heavy clunk/crunch ocurred. Then while in 2wd and travling down the road at about 30mph and shifting on the fly into 4 wheel high the same heavy clunk/crunch occurs. Is it that the older systems like that don't synchronize? Or is there possibly a problem with the transfer case?

 

You will be able to hear, possibly feellight clunkof the shifting in and out of 4x4. I know the low range shift feels a bit harsh but it is not too bad. I have had my truck for 6 years (157,000 miles) and have had no problems with the transfer case. Just make sure that if you buy that truck, that you back up when shifting out of 4x4 to free up the tension on the transfer case, or it will stay in 4x4 for a bit until the tension allows for the shift. Good luck and test drive the hell out of it to make sure that it is what you want. Good luck.

 

I talked to a GM certified mechanic right after I bought my truck because it was making noise in four wheel drive and he told me when shifting into 4 Hi you should be moving about 20 mph and keep it in drive. When shifting into 4 Lo you should be moving around 5 mph and put it in neutral. When I did this my four wheel drive didnt make any more noises other than the slight clunk of engaging and disengaging!

 

4 Lo will be pretty loud, evey truck I have ever driven was loud going into 4 Lo. 4 high will make a noise, you will feel it in the steering a bit, and you will hear a muffled, low "whiiiiiir" from the front end when the you hit the gas (and it is in 4 Hi or 4 Lo). All that is normal. You can pretty much hit "Auto4" anytime, "4Hi" I would be moving (no particular speed), but try to keep it under 60 when shifting into "4Hi". "4Lo" Id say right at 5 mph, no faster then that when shifting. "4Lo" shifts are harsh.