engaging 4wd

Im a new GMC Suburban owner who isn't sure how to engage the 4wd. I last owned a 1996 Ford F350 with locking hubs so engaging 4wd required I get out of my truck, lock the hubs and then shift the lever to 4high. On my 97 Suburban there are no locking hubs so do I engage 4wd while stopped or while driving at low speeds? I would consult my owners manual but the previous owner lost it. Any help would be appreciated because I don't want to mess my transmission up.

On my 03 K2500, 4-HI can be engaged on the fly at any speed while 4-LO can only be engaged while rolling 1-2 mph(recommended). This is a push button system that will not engage unless conditions are right as opposed to the manual shift lever type. Hope this helps-what year is your vehicle?

Regards, gb

FYI: You can buy new owners manuals (and service manuals) at www.helminc.com

//2000CAYukon

4HI and AUTO 4WD are shift on the fly as long as both front and rear axles are turning the same speed. 4LOW should be stopped with the tranny in neutral. Like the "Yukon" says, spend the money, get the manual and read it.

Is your system push button or is it floor shifted. GM's Instatrac System is an on the fly system for 4wheel hi, and 2wheel hi. To shift into 4wheel low you want to be neutral and you want to move the lever in a quick smooth motion. When shifting to 4wheel low the gear ratios are lowered significantly and if you shift the lever too slowly you will wear the transfer case out. Also GM's Instatrac system is NOT to be used on dry pavement, or sturdy ground. Instatrac is a part-time 4wd system so all four wheels always spin at the same speed. If you engage it on pavement while turning you will basically twist up your driveline. Sometimes you actually get better traction in the snow in two wheel drive. You should only use 4wd when you're stuck.