I didn't say it did not operate at higher speeds. I said it always operates from a standing start. I stand by my statement. But in any case I was simply trying to make sense of the original comment.

The Ford literature indicates it works at higher speeds, although I have not seen in with my SG. But I don't monitor AWD very oftern.

 

wwest: you continue to reconfirm that you have little to offer here. You should not modify others posts like you did when you added the word rarely to my post in quoting me. Your addition was far from correct. Out here where I live we use 4wd alot in the winter and a good bit in the spring mud season (should I tell you just how long Wyoming winters are?). So please don't do stuff like that.

That is the OEM front axle on that Suburban, so at 435,000 miles & 19 years, it's had its chance to show off.

Since the power coupling device on the front of the rear axle couples the rear axle in & out of power with the front driveline on a continuous basis, the windup thing that happens in part time 4WD cars is not likely to be a big deal here. That's why I called it irrelevant to the issue.

When you try and interpret other's posts you just seem to always get it wrong and mislead people. Please don't do that.

 

+1

 

In ~01 our '92 Jeep Cherokee Limited was relocated from Seattle to north central MT. The '92 has a full time 4WD mode that uses 3 open diff'ls and thus will really only drive all four wheels with roughly equal traction on all four.

Since it went to MT I can only think of one instance wherein the Jeep had to be placed in 4WD "locked" mode, and that was in early spring when one of the back "roads" (cow path) on the ranch was seriously wet and muddy.

Having lived in that area of MT back in the sixties I think I am qualified to attest to the fact that TRUE/enforced/locked 4WD mode is in actuality rarely needed/required.

If you use the locked mode, driveline windup, tire scrubbin mode, of your 4WD system more than rarely, even in the back country of Wy I'd find myself very surprised.

 

"..not likely to be a big deal here.."

Then what is your alternative explanation for all the premature PTO/PTU failures and/or the PTU/PTO "blown" and leaking oil seals.

"..always get it wrong..."

No, I stand FIRMLY behind my statement that YOU make use of the part-time 4WD mode, driveline windup, tire scrubbing mode, of your Suburban...

RARELY.

To say otherwise would put you in the idiot category and we both know well that isn't the case.

Leaving your Suburban in locked mode except when actaully needed/required puts you and others in danger.

 

Bill,

You are quite obviously aware that having the front differential LOCKED into synchronization with the rear differential on a highly tractive surface is detrimental, overstresses, the ENTIRE drive train.

But that's what these new "full-time" 4WD systems do the clear majority of the time, even in your country. Did Ford truly design the entire drive train with enough robustness to remain intact in the Los Angelos daily stop and go traffic, no slippery roadbeds except for teh rare and short-lived oil and rain soaked roadbeds...??

It seems to me that these new F/awd systems would be best served with an manual PB switch enable for the driver to put the 4WD mode to use ONLY for known slippery roadbed conditions.

 

The Ford AWD does not engage full time, so I'm having a difficult time understanding your arguments. I engages selectively, although always from a standing start. Ford calls it an "intelligent" system.

 

Statistics do not lie. There remains zero statistical evidence (as always) of support to his statements. This is from one who claimed "Lexus wanted to hire me to teach their ...". Endless bunk continues.

 

stevedebi: remember that this is the guy that some years ago told people that they should put 75w-90 gear oil in their transaxle.

Yeah you got it right. The power coupling device on the front portion of the rear axle engages the rear axle when the computer system calls for it. As I understand it, this is rarely engaged 100% of the time. Much of the time on a hard surface road it is likely at 0% or maybe 10-20% of the time.

Thus, as you noted, the windup issue is really a non-issue on the AWD FEH.

Of course it was a big issue on my Suburban when I came within an ace of lunching the front axle! But those little puffs of white smoke from underneath tipped me off!

 

As mentioned a few posts above, rear wheels are engaged "every" time you leave from a dead stop and gradually drops to zero as you reach a constant speed. I often wonder if there is a certain speed at which it drops off as it "seems" to be zero between 25-30mph.