4th generation 4x4 Explorer (not AWD)

[Boomyal]

Trying to get this all straight. It seems a 4x4 is really a semi-AWD? My understanding is that unless you turn of the RSC, the system will transfer power to the front wheels any time rear wheels start to slip. This action takes place via a clutch in the in the transfer case?

If this is so, there must not be any hubs in the front wheels. There is also no apparent way to disengage the front wheels and driveshaft from the transfer case. That means the front wheel are always turning back thru the front differential and driveshaft, into the transfer case?

In my '94 Suburban, engaging 4x4 High, locks hubs in the front wheels. Otherwise, even though the front driveshaft may be turning, the front wheels are turning free.

 

[Alan Lloys]

You are correct that the AWD label that carried over to 4th generation mountaineer is really a bit of a misnomer for the V8. It is really an automatic 4x4 system and is near identical to the Explorer version. Only difference is that the Mountaineer does not have the low range option the Explorer has.
Supposedly the electric clutch to the front wheels will have an 5% front and 95% rear power until rear wheel slip is detected. When wheel slip is detected from the rears the electric clutch will engage and the fronts will be locked 50% - 50%.
You can also lock the 4x4 manually via the communication center in the vehicle. It does not have the separate buttons the Explorer has.

I was looking into this at depth and I have the full repair manual for the vehicle which explains how it works.

The V6 has the older fashion AWD with a viscous coupling which is a mechanical AWD system if I remember correctly.

 

[Ronin8002]

Trying to get this all straight. It seems a 4x4 is really a semi-AWD? My understanding is that unless you turn of the RSC, the system will transfer power to the front wheels any time rear wheels start to slip. This action takes place via a clutch in the in the transfer case?

If this is so, there must not be any hubs in the front wheels. There is also no apparent way to disengage the front wheels and driveshaft from the transfer case. That means the front wheel are always turning back thru the front differential and driveshaft, into the transfer case?

In my '94 Suburban, engaging 4x4 High, locks hubs in the front wheels. Otherwise, even though the front driveshaft may be turning, the front wheels are turning free.

Yep, you're correct. The front wheels are always engaged with the front diff and driveshaft, just like the rear wheels. Like Alan Lloys said, the transfer case allows about 5% power to be applied to the front driveshaft during normal driving when in auto 4x4. Once a wheel slippage between front and rear wheels is detected via the ABS sensors, the transfer case engages so that there will be more power applied to the front...up to 50%. If you go into 4x4 Hi, you are essentially forcing this process manually.

This is why it is so important to have a spare that is sized the same as the rest of your tires. If you went say to 265/75 tires and kept the stock spare, the stock spare would be unusable due to the fact that the auto 4x4 system would see the smaller diameter (and therefore faster turning) tire as wheel slippage, and would attempt to engage the front axles to compensate. It would also probably play hell with the advancetrac...neither of which would be a good thing for the drivetrain on dry pavement.

If you want to read more about the way the transfer case works, go here:

http://www.google.com/url?q=http://...kQFjAJ&usg=AFQjCNFjTUDq7MFowQTDRi4V-bJZxGIg3g

 

[Boomyal]

Good read, Ronin. That really helps explain, why in this current snow storm, my new 2006 Explorer seemed to be able to go where no 2 wheel drive cars were able to, even though I had not selected 4 wheel High.

All this electronics, however, make me nervous and I am still not understanding how a system can transfer 5% of the power to the front on a continuous basis.

 

[thebrakeman]

The last 3 years, I rarely had my Mountaineer out of AWD (aka-Auto 4WD) mode. This year, with all the snow we've had, I have thoroughly enjoyed locking the truck into 4x4Hi. In the snow, it's so much smoother to lock the axles together, and not have the system clunking like crazy, engaging/disengaging. As long as the road surface is slippery, I have to think it's better for longevity, too (versus working that electrnic clutch constantly).

 

[Boomyal]

......(versus working that electrnic clutch constantly).....

Yeah, I wondered about that.

 

[CharlieH81]

This thread is helping me understand this too. I want to go to something like a 265/70 on my 06 XLT but am kind of worried based on what some are telling me, that the larger size could affect the Auto 4WD.

 

[Ronin8002]

This thread is helping me understand this too. I want to go to something like a 265/70 on my 06 XLT but am kind of worried based on what some are telling me, that the larger size could affect the Auto 4WD.

The larger size isn't an issue, provided all 4 tires are the same size. Meaning that you need a spare of that size also if you want to be able to use it.

I just bought 5 wheels and tires of the same kind. That way I just do a 5 tire rotation every time I change the oil and it's all good. No issues with auto 4wd.

265/70 or 265/75 will fit in the spare tire area...it's tight but it will fit. Anything bigger likely won't.

 

[CharlieH81]

Thanks Ronin

 

[Gargoyle]

2008 Ford Explorer Transfer case

Actually the 2008 Explorer uses the Borg Warner 4412 transfer case not the 4411 as described in the link above - they are very similar ...

 

[Boomyal]

Actually the 2008 Explorer uses the Borg Warner 4412 transfer case not the 4411 as described in the link above - they are very similar ...

...and what difference does that make???

 

[Ronin8002]

...and what difference does that make???

As far as increasing tire size, nothing that I am aware of....provided all tires are the same size.

 

[Gargoyle]

An observation about Auto 4x4:

I have an 2008 explorer with V8 and 4x4 and is normally driven in auto 4x4. I have always noticed a bit of vibration at low speed in second gear while acceleration which I attributed to the engine. Also my front tires leave a dark trail on my concrete driveway when making a sharp turn to get in and out of the garage. Recently I noticed that the transfer case seal to the front drive shaft was leaking badly accompanied by lot of play in the t. case. I had a brand new transfer case installed, no more leak but the vibration and the dark trail remained. I removed the fuse for the 4x4 system and both the vibration and the dark trail totally stopped. I think the chain drive causes the vibration - I have noticed others in the forum have the same vibration. Other than having the wrench light always displayed in the console, I have not noticed any problem with the fused removed and I only use the 4x4 occasionally in the summer.

 

[Beargap]

I have an 2008 explorer with V8 and 4x4 and is normally driven in auto 4x4. I have always noticed a bit of vibration at low speed in second gear while acceleration which I attributed to the engine. Also my front tires leave a dark trail on my concrete driveway when making a sharp turn to get in and out of the garage. Recently I noticed that the transfer case seal to the front drive shaft was leaking badly accompanied by lot of play in the t. case. I had a brand new transfer case installed, no more leak but the vibration and the dark trail remained. I removed the fuse for the 4x4 system and both the vibration and the dark trail totally stopped. I think the chain drive causes the vibration - I have noticed others in the forum have the same vibration. Other than having the wrench light always displayed in the console, I have not noticed any problem with the fused removed and I only use the 4x4 occasionally in the summer.

The vibration is likely the transfer clutch engaging. The way it shifts varying amount of power to the front and still releasing driveline stress in turns is by engaging the clutch pack many times each second and varying the length of time it stays closed. So, in normal situations it is closing, say, 50 times a second (I forget the actual frequency) and only staying engaged 5%, but as slippage is detected that increases to perhaps 90% closed in each cycle.