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Auto 4 wheel drive

i have a 1999 chevy suburban with auto 4 wheel drive and a option for regular 4 wheel drive. what is the difference? and is one better than the other?

Have you checked your manual?

no i no longer own the manual but while searching on this site i think i found the answer

The “AUTO” setting will cause it to automatically engage the 4wd when it detects slippery conditions. The other settings are basically manual overrides for if you’re on a consistently slippery condition like driving on a completely snow-covered road and you don’t want it constantly cycling between 4wd and 2wd. Don’t use the manual 4wd setting on a dry surface!

If it is like my 03 trailblazer, here is the scoop.
2wd is 2wd only
auto engages the front drive shaft and kicks into 4wd as needed,
this setting reduces gas mileage but is my preference on snowy days.
4hi locks it into 4wd further reduces gas mileage and is 4wd all the time.
I don’t know for a fact but think it may affect handling in an adverse way
4lo adds extra torque like when you need to pull your boat out of a pea gravel or sand launch.
My experience with the auto has been very good, I have not had a problem with constant cycling. I don’t know why this 4wd would have any more trouble than any other all the time 4wd, can you go into more detail GreasyJack?

My experience with it in trucks I have plowed with (nothing real new), is that it’s not the same as awd, but as “Gressy” said, just automatically engages the part time 4 wd mechanism. When in 4 wd the drive train bias is not as variable as a true awd and therefore may have negative high speed handling quirks. Still, a decent functional alternative to staying in 2wd or 4wd all the time for truck application.

I have an '04 and did a bit of experimenting when I first got it. I found it to be quite stable during transition. It’s a lot smoother than I expected. For the most part, it only engages when you’re accelerating away from a stop. I suppose if you were cruising along and romped on the gas it might engage but that would be foolish operation. It’s a great feature IMO. No steering bind on cornering and yet, you get the advantage of 4HI when conditions warrant.

I don’t know the particulars of the system innards but I suspect that, unlike traditional 4WD, the system is partially engaged in the AUTO mode. Only on slip detection are the hubs locked for example. So there are things working while the AUTO mode is engaged and those things can break or wear out.

I know what you mean about things can break and wear out but 100k + and still going good. I don’t know for sure as I leave the odometer in trip mode and unlike the guy with the Tacoma waiting for something to go wrong, if I don’t know how many miles it really has, I don’t need to expect any problems. In my old age I have a good mechanic do the work as I and he deem necessary, I could not even see the spark plugs, but at 100k had them replaced, per owners manual.

Like the others said, the AUTO only engages the 4wd once you’ve started slipping and then goes back into 2wd once you have traction again. This is great for on-road slippery conditions where you can’t use 4wd most of the time. But in deep snow or mud or other consistently slippery conditions, you want it to stay in 4wd so it doesn’t slip in the first place so that’s when to use the manual 4wd settings.

My suggestion is to find an owner’s manual on-line. Even if your current question is answered, you should have one. Read it cover to cover, it will be well worth the price.

I read the manual cover to cover and there were 5o pages on seat belts, and 1.5 pages on trans of little info, It does not even cover headlight or side marker bulb replacement.