Auto 4, How's It Work?

[darkfox1]

I tried searching for this but I couldnt' find anything.

 

So.. how's Auto4 work? I've been using it in the rain because I simply can't take off without spinning tires if I'm making a turn or come to a stop at a redlight on a hill. It works like a charm.

 

today I actually tried to spin tires in auto 4, just a hard launch.. didn't spin one bit..

 

hows auto4 work? and how's it differ from 4hi?

 

thx.

[Matt_]

cliff notes: there's a clutch in the tcase that engages the front axle when the computer senses wheel slip.

 

however, it is a bit more complicated then that. basically, there are other "conditions" that result in power to transfer to the front axle. One of those being starting from a dead stop... hence why you can gun it from a dead stop in the rain and not spin out.

 

in 4wd, the clutch is fully engaged.

[darkfox1]

Fair enough.

 

It seems around here it's a running pun with the state to put a redlight halfway up a steep hill. in 2hi I just can't take off even slowly.

 

auto4 has been a blessing for those days.

 

Thanks for the explanation!

[KMGZ400]

is it bad when you floor it in auto? like, is it rough on the clutches or anything? i never uses auto because im afraid it will damage it if i start to spin pretty good in the rain

[Matt_]

i wouldn't worry about it.... that's what its designed for (well, i wouldn't floor it every chance i get just try to spin the wheels. but using it normally won't hurt anything)

 

The T-case is a lot stronger than the axles in these trucks- id be more worried about them

[uchi]

it engages quite nicely. i tried it out when we had our last big rain fall last week, hammered the gas off the line, the back tires might have spun for a half second if that, the fronts kicked in and she took out. transition was fairly smooth aswell. very impressed. cant wait till we get crap loads of snow

[music]

Engages so smoothly and quickly that you don't feel it. At a dead stop, I can't spin the tires on a wet hill in auto-4wd (which is what I want it to do). I'm stock though (i.e., full TM). If TM is removed (tuning), I wouldn't go WOT on pavement from a dead stop with auto-4wd engaged. There's no place for the torque to go, except into the axles and gears. Can't be good...

[KMGZ400]

hmm well its pouring rain today so i guess ill try and play with it... my tires always break loose in the rain.. gets annoying. we'll see how smooth my 2001's auto 4wd is.

[Wires]

After I put the magnacharger in my '00 5.3l, I used auto-4wd all the time. It had no problem dealing with power when you'd hammer it from a dead stop (you do have 4 tires taking the power vs 2).

 

The only downfall, is in auto-4wd, the front diff is engaged, so low speed/tight corners can cause the tires to slip and chatter, which is stupid bad for the front gears (like in a parking lot). Best to go back to 2wd in those situations.

 

I liked it as I never had wheel slip if you laid into it, and unlike straight 4wd, it wasn't coupled front/back all the time, so you didn't get the driveline noise from the differences between the wear in the front and rear tires (rears tend to spin more, so they are slightly smaller).

[darkfox1]

I love the auto4 in the rain. I'm glad I'm not the only one that's used it this way lol.

 

I love northwest of ATL so we've got the foothills action going on. My fuel econ falls about 2mpg using auto4 vs 2 but if I can actually drive.. it's a worthy sacrifice on rainy days.

[aaron8301]

You guys in the South have no idea... I live in Western Washington. I HAVE to use the auto 4 to prevent.... getting a ticket from going sideways down the road. Seriously, even on tight curves (not just turning in an intersection), I can kick her sideways and hold it there (I love the way my 'Burb drifts). I'm amazed at the torque the 5.3 has. Even the wife (who drives like a granny) uses the auto 4 in the rain to prevent wheel slip.

 

On topic: from what I know, when you engage the auto 4 the front diff engages (like 4-high or low), but the clutch in the T-case to the front drive-shaft only engages when the ABS sensors report the average speed of the two rear wheels is X-mph higher the the average of the two front wheels. Then once you let off the throttle a little bit, the clutch releases. Since the front diff is engaged, mpg will suffer.

 

Now I have to tackle the knock sensors next weekend; she's lost half her oomph.

[TRCM]

Wow, guess I drive like an old man, as I have no issue with wheel spin unless I want it

[gates59]

I thought 4x4 was only to be used on snowy roads. I also have never seen the point of using it on wet roads. Never spun out the tires yet. You know it is slipery so you drive for the road condition.

[darkfox1]

There's a place in my commute that I can't even take off slowly in dry weather without spinning tires. Driving for conditions doesn't help you.

[uchi]

im pretty easy on the throttle myself, i find i get much bettre gas milage, but there are times when you need to pull into a parking lot for example on a busy street in the rain and that window to get in is small. the auto feature helps there. i had the back tires get loose on me the other night in just this situation, i barely touched the gas and the road was slick enough that she started to spin. i made it through the last 4 years in 4wd vehicles using only 4wd when i needed it, or to blast through the odd snowbank here and there. having owned a pickup truck before i know how much fun they can be in the snow in only 2wd so the 4wd auto will be great for the bad days when i dont want to put more wear on the system using 4x4. also when the wife drives the truck itll give me piece of mind knowing she isnt going sideways into on coming traffic, a pole, more on coming traffic, a curb, group of old people, or a pole.