The inner axle shaft and the clutch shaft have teeth and they are connected by a sliding sleeve when you select 4WD. If the teeth are not perfectly aligned, the sleeve will not slide. The two shafts do not rotate at the exact same speed, but close, so moving the vehicle at any speed will align the teeth so the sleeve can engage the two shafts together.

 

Ok guys I have the 4 button 4x4 and lately almost every other time I try to engage it it grinds but, it always changes over and gets me out of whatever I'm in. Is there a way I could stop this grinding all together? Posi lock mod? Even auto4wd grinds in the switch. Usually I'm giving it a little gas but far from the floor and I used to be able to do this without any grinding but this winter season it's been grinding I'm worried about the longevity of my transfercase and 4wd parts. Any suggestions?

I don't mean to thread jack but I've been having trouble getting replies to any threads I start lately

 

Does it grind on a snow covered road or just when you put it in 4wd on a dry surface? Are all of your tires matching?

 

my 96 blazer without electric shift says to put it in park to go from 4hi to 4lo.
read your owners manual for proper operation. if you don't have 1 a quick google search and you'll find 1

 

I only engage 4wd in the snow or off-road never on dry pavement so to answer your question yes it grinds on the snow but I don't know about dry pavement, and three of my tires match the other is the spare it's on the front drive side

 

If there is any height difference in your tires it can have an effect on it but that usually makes a "pop" sound not an actual grind. Even if one is slightly different that shouldn't effect it on a snowy or off road terrain. How's the oil in your t-case? Have you ever noticed any metal shavings in it?

 

Tcase oil.... Never looked at it and my dad and I have had the blaze since new....

 

The NV236, (Auto 4 button), has a clutch pack and needs regular fluid changes every 50K miles, maximum. Fluid change takes just under 2 quarts. Gotta use this stuff, available at any GM dealer:

 

the way i always do it, same as disengaging it, is put it in neutral pull the lever or push the button. wait a second, back up about 2 feet then go forward.

 

for sure the best way to engage,last thing your drivetrain needs is more stress