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Outbackers Contributor
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Outbackers,

I bit the bullet and spent DOUBLE what I usually spend at Grease Monkey and got a Mobil 1 full synthetic oil change in the Yukon XL. I figure with the mountain towing coming up this summer the engine would apreciate it. I recently did the transmission service but didn't do synthetic there. Oh well.

If you have a 4x4 vehicle, do you tow in 4x2 or 4x4 mode? What is recommended by GM / Ford / Dodge? Up to now, I always tow in 4x2 mode. But it occurred to me yesterday that towing in 4x4 mode would distribute the extra work on the transmision to both front and rear wheels. Is that true? At the same time, I wondered if 4x4 mode causes the engine to work a little harder since it has to drive 4 wheels instead of 2 when in 4x4 mode. Let me have it, guys.

Yesteday I took the Outback to the dealer to fix 7 minor issues (including that A/C thermistor issue previously discussed). I noticed that while climbing some semi steep grades on the far west side of Denver that the truck shifted down two gears at times which brought RPMs to around 4000 while traveling 50 - 55 MPH. After about 45 seconds in that gear and speed, I smelled burning.

I have the 5.3 liter V8 with the 4.10 gears pulling a 26 RS, so I am at least 2000 pounds below max towing. After that short tow up some semi steep stretches of highway yesterday, I wondered how anyone with a smaller tow vehicle can get around without REALLY taxing their vehicle. I guess if you live where it is mostly flat, the towing issues diminish.

Thanks everyone, Randy
 
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Randy,

The only time that I would tow in four wheel drive is when I couldn't get enough traction in two wheel drive. Then I would seriously consider whether I needed to be towing at all under those conditions.
Four wheel drive puts a little extra load on the engine, but the biggy is the load on the steering system on dry pavement. Some vehicles have full time four wheel drive and all wheel drive, but their steering is designed for it.

That burning smell when you were pulling a steep grade is not all that uncommon. When your transmission downshifts under a heavy load the clutch pack slips. If it slips a lot, it burns. That's not good. The best way to avoid it is to shift to a lower gear before your vehicle gets to the incline, that way it's not trying to shift under such a heavy load. The synthetic oil also helps.

This is just my opinion, so don't take it as gospel. I think that the more you learn about your equipment, the better off you are.


Happy camping,

Gary
 

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I keep mine in 2 wheel drive when towing, have yet to have a need for 4 wheel while towing. MPG is bad enough while towing, but towing in 4 wheel would really suck... the gas that is
 

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Randy,

Unless your vehicle is designed for all-wheel drive operation (always on), I would not recommend towing in 4-wheel. For example, my Ford is a standard 4-wheel drive with manual and vacuum (lever on the dash) locking hubs, and the owners manual specifically mentions not to drive on dry pavement with 4-wheel engaged (towing or not). The only time I use 4-wheel drive is when I'm off-road or in heavy snow and ice. Then it works great.

Chet.
 

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Well, it seems everyone has answered your questions already, so I'll just expand on your answers some what.

All Wheel Drive vehicles are not the same as 4 wheel drive vehicles. You should not drive in 4WD on dry pavement, as stated above. The reasons for this are primarily a matter of geometry. When in 4WD, your front axle and rear axle are connected. However, when you make turns, just as one wheel on the rear axle turns at a different rate then the other, the wheels on the front axle turn at a different rate then the wheels on the rear axle. Unlike in a differential, there is not normally a mechanism to allow for this difference in axle speeds. This causes binding in the drivetrain, and could lead to pre-mature failure.

When you are in slippery conditions, then the binding forces are able to work out by letting the offending wheels spin faster or slower to keep things right.

AWD vehicles, (like my wife's Honda CRV) have a way of dealing with this binding, and I'm not real familiar on how it works.

At least, this is my understanding. I'm sure one of the mechanical types hear can give a better explaination, and correct any errors I may have made.

Tim
 

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Tim,

I'm no expert either, but I do know that Subaru has a super-duper high-tech presentation on their AWD systems at:

http://www.subaru.com/allwheeldrive/all_wheel_middle.jsp

If you look under "View AWD specs" and "Drivetrain" you can see that they just use a center differential between the front and rear axle. I can speak from personal experience that the AWD my old Subaru worked great for wet, snowy, and icy Pacific Northwest roads.

Of course, all this is much more than anybody cares about AWD vs 4WD (especially Randy), but ahh well...

Chet.
 
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