Auto 4WD

[james21]

Ever since I have had my AV, I would use the Auto 4WD on the highways for better control at high speeds. But for about 7-8 months, I have been using it for normal everyday driving, and usually turn it off when turning from a stop or making more then a 45degree turn. I have noticed since I started using it everyday that when accelerating from a stop, for instance from a traffic light, that the rear will sound like the wheels are slipping or skipping as if I were on ice.

Iam just wondering if anyone else has come upon this issue, or if anyone has an idea why it does that.
I appreciate anything you guys can give me.

Thanks, James R.

 

[TXAVy]

Haven't had that issue personally, but then I don't use Auto 4WD on dry pavement either. 4WD doesn't like having all 4 tires solidly planted on pavement so I avoid it. I just engage 4-Hi whenever it rains to make sure that the front end gets some revs and stays lubricated.

 

[ultravorx]

That maybe the "clunking" noise i had with my auto 4wd system. Once again GM dsaid its normal! I dont see hows its normal if the problems starts over time. Just bring it in to the dealer and tell em whats wrong. Just make sure they dont say "Its a loose ground bolt making the noise" , thats the excuse they gave me!
Frank

 

[jgwatsonjg]

That maybe the ?"clunking" noise i had with my auto 4wd system. ?Once again GM dsaid its normal! ?I dont see hows its normal if the problems starts over time. ?Just bring it in to the dealer and tell em whats wrong. ?Just make sure they dont say ?"Its a loose ground bolt making the noise" , thats the excuse they gave me!
Frank

THE A4WD IS NOT TO BE USED EXCEPT Where SLICK Conditions MAY BE PRESENT. Not at HIGHWAY Speeds Not on DRY SURFACES.

Our A4WD Does not have the Viscouis[sp] Coupling Like the Escalade's or the Silverado SS' have.

Only use it if you need it. ?You Probably Ground up the Ring And Pinion.

Just my 2c.

Agent M.

 

[RichUF]

First of all, we don't have AWD, we have part-time 4WD...very distinctly different.

Secondly, driving in AUTO 4wd *should* not cause any binding of anything, whether turning or not, on dry pavement assuming that there is no wheel slippage (which is a pretty good assumption given that it is DRY pavement). If there were to be slippage on dry pavement (I'd have to question why) then yes I'd worry about binding.

There are some excellent existing posts complete with schematics of the system from the service manual and good descriptions from members of their operation.

All of this said, I wouldn't drive in auto 4WD on dry pavement, not because of fear of damage particularly, but more because it would seem to serve absolutely no purpose. In fact, I've never had slippage with my driving style during rain, so I don't use it then either. Of course, my tires are new.

I'm no mechanic...anyone disagree with any of this?

 

[james21]

Rich, I would have to disagree with you on a couple of points.

First, the wheels do bind up when turning at or more than 45degrees, and I would think that this would severely damage the axle or 4WD system.

Second, I use my Auto 4WD when it is raining because it does help with traction. I also have noticed that the truck will stop quicker with the Auto 4WD engaged rather than 2WD; I know this because I have tested it extensively after a near miss with another cars rearend when I had it in 2High.

Third I have found that the Auto 4WD does make the the truck more stable when going around turns, and the noise will only occur if I have it engaged when I am accelerating from a stop.

-James R.

 

[olsontru]

I thought that from prior reading somewhere in this forum that A4WD did nothing until slippage was detected then it kicked in (somewhat sluggishly, if I recall). I can't fathom how this could produce better braking or stability.
IMHO

 

[james21]

Olson, everybody has their own opinions, but in my opinion, I have experienced better stability at high speeds and better braking when I have the Auto4WD engaged.

-James R.

 

[bekind]

I must concur with the majority here. There should be absolutely no reason what so ever to run in A4WD on dry pavement. You are just asking for premature wear. I can't even understand why it would be needed, it is already super difficult to get the tires to spin on dry pavement. And, there really is no added bonus to braking or handeling when in A4WD as the front end is not even recieving power unless there is slipeage. And if you do slip while braking A4WD does absolutely nothing, that's what ABS is for.

I do disagree with the sluggish engagement statement earlier, in my Tahoe it is seamless and lightning fast!

~bekind

 

[Tree_Hugger]

Yep, what he said!! But was I right as well... huh, was I? ?

Well...
Not when you said he wore something out

I don't know why everyone has conniption fits about 'wearing out' their front differentials when they are spinning. (All the Jeep guys did/do about the TJ's always spinning front end, too) . You don't worry about 'wearing out' your rear differential, do you? Well, then...
I can't detect ANY change in instantaneous MPG when maintaining a steady speed on level road and switching from 2WD to Auto4WD and back. So I think any 'friction losses' are trivial.

I switch into Auto4WD whenever it rains, and I don't worry if I forget to switch back for a while....
Yesterday I realized I'd been in it for 2 dry days . There is NO PROBLEM (and, I agree, no point either).