# Towing In 4x4



## jlbabb28 (Feb 27, 2006)

Ok I was talking with a freind of mine last night that tows a heavy trailer. 13K Pounds bumper pull, in talking with him I expressed concern about towing my new TT and some of the hills. He said when he climbing a grade in his truck if he is going under 50mph he will use the 4X4 high mode to assist him in towing.

He said it doe not give him anymore power but rather than one tranny and one read end doing the work he is sending some of the stress related to that tow to the front.

He claims since he started doing this a 25 degree drop in tranny temp has occured. I checked my owners manuel and it says under 50MPH I can use four high.

What do you all think, I understand the concept, but may not go much further than that. I drop in tranny temp is a drop after all.

Jeff


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## Herbicidal (Aug 29, 2003)

That's an interesting idea. I have a 4x4 but it never crossed my mind to put it into 4wd while towing up a decent grade. I have a tranny temp gauge with the sending unit in the tranny pan. Does your friend have a tranny temp gauage or is the 25 degree drop in temp a guesstimate?


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## jlbabb28 (Feb 27, 2006)

No I have seen the guage it's in a pilar mount setup from the tranny pan.

He claims it really helps, like I said I understand the concept but dont know if I could reach down and drop it in to 4X4

Jeff


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## Herbicidal (Aug 29, 2003)

Yeah, I hear you on that!







I won't even be able to give it a try for several months, at the earliest.


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## PDX_Doug (Nov 16, 2004)

Hmm...









I think the first thing I would do would be to check your owners manual. My hunch is that it is going to recommend against such a practice. Unless you are experiencing slippage of the drive wheels, switching into four wheel drive is really not going to do anything for you. And there is a real risk in running four wheel drive on dry pavement. Again, I believe your manual will instruct you to use your four wheel drive in slippery conditions only (Snow, ice, gravel, etc.)

As far as the transmission temperature is concerned, two wheel drive or four, all the power from the engine is passing through one transmission. Therefore any heating due to load is still going to be present. Granted you may see a drop in the temperature of the rear differential, as it is not working as hard with some of the load being transferred to the front differential, but the transmission is still working just as hard.

So unless the hill you are climbing is so steep, or the traction is so bad that you are spinning your wheels, leave the transfer box in 2WD mode, and save the front end of your four wheel drive drive train the wear and tear.










Happy Trails,
Doug


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## jlbabb28 (Feb 27, 2006)

You know this was my thinking as well, the one tranny is doing all of the work but just dividing it between two drive axel's via the transfer case. i have done some other polling this morning amoung other friends who also swear by the practice too.

I can remember growing up going up grades hunting that the entire convoy of trailers would stop and have to go into 4LO to get to the right reduction of gears to make certain hills while towing trailers. This was the late 70's when trucks did not have the power they do now.

Again I dont think I have the (insert what ever word fits here) to reach down at 45 and drop into 4X4 mode.

Jeff


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## matty1 (Mar 7, 2005)

my manual states:
Driving in the 4-WHEEL HIGH (4HI) or
4-WHEEL LOW (4LO) positions for a long time
on dry or wet pavement could shorten the life of
your vehicleâ€™s drivetrain.


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## battalionchief3 (Jun 27, 2006)

Im not sure how the transfer case would like that. If it does drop the temp of the fluid does it then pass it on to the transfer case? Most modern ones run on ATF while older ( my opinion better )ones run on gear oil and we know what heat does to ATF. The other factor is making a turn, even a slight one, the transfer case and front end tend to buck due to the tires not slipping on dirt and that destroys transfer cases. I would feel better putting a deeper pan and bigger external cooler on then pulling it in to 4wd.


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## N7OQ (Jun 10, 2006)

I have to agree with Doug, everything goes through just one transmission and every 4X4 I have had does not recommend running in 4 wheel drive on pavement for extended amount of time. The extra load on the transfer case can not be good for it. I think if you are having a heating problem a bigger transmission cooler would be better.


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## campmg (Dec 24, 2005)

N7OQ said:


> I have to agree with Doug, everything goes through just one transmission


Sounds like if you tow in 4 wheel drive you may go through a few transmissions.


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## Oregon_Camper (Sep 13, 2004)

campmg said:


> Sounds like if you tow in 4 wheel drive you may go through a few transmissions.


small price to pay to get to that perfect campsite.







(kidding of course)


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## Reverie (Aug 9, 2004)

I don't pretend to be an expert but wouldn't putting the truck in 4-Wheel High INCREASE the amount of stress on the transmission? Now, instead of pushing torque through the transmission sufficient to drive equipment to power two wheels (transmission, driveshaft, rearend (ring and pinions)), you will have to push enough torque through to power four wheels with double the complexity PLUS the Transfer Case. I dunno but seems like it would suck up additional power like Roseanne Barr at an All-You-Can-Eat Ice Creme buffet.

Reverie


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## PDX_Doug (Nov 16, 2004)

Reverie said:


> like Roseanne Barr at an All-You-Can-Eat Ice Creme buffet.


Thanks Rev!








That's a visual I needed right before our offices' holiday lunch!









Happy Trails,
Doug


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## Scoutr2 (Aug 21, 2006)

Another factor to consider - are the front transfer gears designed to pull that heavy of a load?

My experience would tell me "No." Most manufacturers have quit "over designing," due to pricing competition, profit margin, etc. I would bet that the front gear train was designed to safely pull only to the GVRW, which does not include the added weight of anything being towed.

That's a lot of expensive mechanical components up front to find out the hard way!

Also - the transmission oil temperature drop that has been observed is most likely due to the fact that as you climb, you gain altitude. As you gain altitude, the air temperature drops, which will cool the ATF more. (And depending on the design, as you gain in altitude, the electronic fan will be directed to turn faster, due to the fact that the less dense air doesn't carry heat away as fast. So the fan needs to move a larger volume of air per minute through the radiator/coolers. This strategy is employed in all types of vehicles - including heavy equipment and truck engines that operate at higher altitudes.)

Just my $.02 - but something to ponder.

Cheers,

Mike


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## Karma (Nov 13, 2005)

My mechanic says 4x4 on my Yukon XL should never be used on dry pavement. He said the 4x4 option, either high or low, locks the drive train so that equal power is going to different wheels. This means that when turning, some of the tires are forced to spin while the others maintain traction. He said the force this places on all drive train components is immense due to the tires having little ability to slip on dry pavement. He said 4x4 should only be used in the snow, sand or on gravel. 
The Yukon's "all wheel drive" option is different in that it transfers power from back to front and back again, depending where the traction is required. AWD doesn't lock the drive wheels.


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## jlbabb28 (Feb 27, 2006)

Agreed with all of the opinions posted here. Now one thing to think about is this, before the invention of auto locking hubs you could free wheel in 4 high and mabye get the desired effect he was talking about.

Agian mine are not big enough to try this and I think my friend is incorrect in his thinking on this but if he wants to wreck his 30k tow vechicle more power to him, I will not be trying it however.

A good discussion to be had at least by everyone.

Jeff


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## Carey (Mar 6, 2012)

battalionchief3 said:


> Im not sure how the transfer case would like that. If it does drop the temp of the fluid does it then pass it on to the transfer case? Most modern ones run on ATF while older ( my opinion better )ones run on gear oil and we know what heat does to ATF. The other factor is making a turn, even a slight one, the transfer case and front end tend to buck due to the tires not slipping on dirt and that destroys transfer cases. I would feel better putting a deeper pan and bigger external cooler on then pulling it in to 4wd.


I agree here. Not good for the transfer case. AWD vehicles generally use a viscious coupler or a spider gear type carrier to compensate for slip. A regular T-case only uses chains and sun/planet gears. They are not able to slip as much. This would create great amounts of friction in the case, transfering that to heat.

Carey


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## huntr70 (Jul 8, 2005)

jlbabb28 said:


> Now one thing to think about is this, before the invention of auto locking hubs you could free wheel in 4 high and mabye get the desired effect he was talking about.


If you didn't have the front hubs locked, you would be doing nothing more than sending power throught the transfer case to the front axle half shafts.

The manual locks did just that, lock the hubs to the half shafts.

Not that I would know what it is like to think your hubs are locked and pull the lever and go nowhere.....
















Steve


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## 2500Ram (Oct 30, 2005)

I think the topic's been pretty well covered but I will give one more example for when it's good to have manual hubs on 4wd vehicles.

If your in a situation where you need lots of torque but not 4wd you simply put the rig in 4lo, do not lock the hubs. This is very popular with boaters getting huge boats out of the water. Once they are on level ground again the just put it back into 2wd and off they go.

As for shift on the fly 4wd most newer trucks suv's etc say it's safe to shift into 4wd if your speed is under 55mph. Read your manual or look online if your not sure. And it's safe to drive up to 70 mph in 4x4. Why you would drive 70 mph if you really need 4x4 is beyond me.

Just my experiences.

Bill.


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## Sidewinder (Feb 25, 2005)

Locking up the front differential of any 4X4 vehicle on dry pavement is NEVER....I repeat NEVER a good idea. Think about it. When you are in 4WD, something is slipping. Even if you are going in a straight line, a difference in tread wear between front and rear tires or different air pressure setting will cause a differential in the final gear ratio set by the distance between the center of the axle and the ground (the effective radius of your tire). Now hitch up the trailer with load distributing bars and add extra weight to BOTH axles. This makes the slip harder to accomplish. The "slip" WILL occur somewhere. If you run in this condition long enough, the transfer case or axle shaft or drive shaft....something will HAVE to give.

Now turn the vehicle and the issue I just describe grows exponentially.......just a matter of time until you hear a loud POP from somewhere south of your floor board.

DON'T DO IT unless you want to send your mechanic's kids to a better college than he originally had planned for them.

Just my $.02

Sidewinder


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## NJMikeC (Mar 29, 2006)

So I will be better late then never but I couldn't imagine a reduction in trans temp to be true what so ever and would argue it would be higher.

The slower you go the better chance you have of the converter being out of lock. Once it is out of lock you loose the almost mechanical coupling thereby producing an increased amount of slip. The slipping is actually a loss of mechanical power . Since Newton's laws of Physics tell us energy is never destroyed it is only tranferred from one form to the other then the loss of mechanical energy is a gain in heat energy. You are heating that trans up.

Additionally there is also a coupling loss from the trans thru the transfer case evidenced by the heating of the transfer case fluid which actually results in a further loss of torque and power to the wheels.

In short this claim sounds like quite the wives tail to me! Remember 4WD is used to apply power to all four wheels for traction , anybody who tells you it increases power doesn't know too much Physics.


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## Rubrhammer (Nov 27, 2006)

Sidewinder said:


> Locking up the front differential of any 4X4 vehicle on dry pavement is NEVER....I repeat NEVER a good idea. Think about it. When you are in 4WD, something is slipping. Even if you are going in a straight line, a difference in tread wear between front and rear tires or different air pressure setting will cause a differential in the final gear ratio set by the distance between the center of the axle and the ground (the effective radius of your tire). Now hitch up the trailer with load distributing bars and add extra weight to BOTH axles. This makes the slip harder to accomplish. The "slip" WILL occur somewhere. If you run in this condition long enough, the transfer case or axle shaft or drive shaft....something will HAVE to give.
> 
> Now turn the vehicle and the issue I just describe grows exponentially.......just a matter of time until you hear a loud POP from somewhere south of your floor board.
> 
> ...


I agree with sidewinder that something has to give. The first 4x4 I had any 1st hand experience with was my wife's 97 s-Blazer. 1st time I used 4w was in the snow and when I went to back in the driveway the front and back were really fighting each other. It caught me by surprise. The road there was plowed but wet. After that I always made sure to put it back in 2w when conditions didn't absolutely require 4w. As for the into 4w at speed, it had electronic activation and made a very unsettling CLUNK when it engaged and I didn't have big enough ones to do at over 30.


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## Scott and Jamie (Aug 27, 2006)

Another point is that the gear ratio is usually 1 higher in the front end. so if you have 4:10 gears the front is a 4:11 ratio. They do this so the front is pulling the vehicle to help keep it going where you want it to especially when turning. Running on drive pavement will cause binding through out the drive train and can damage the drive train.

Scott


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## Husker92 (Feb 11, 2006)

Seems a bit risky!


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## matty1 (Mar 7, 2005)

2500Ram said:


> Why you would drive 70 mph if you really need 4x4 is beyond me.
> 
> Just my experiences.
> 
> Bill.


Thats why you see so many SUV's off the road during a snowstorm..."But I had it in 4 wheel drive"... and were going 70.

I have no problems with 4hi and dry pavement, not that I do it much, no problems turning or such, but I know my co-workers Tundra and the Ttan protest loudly. (limited slip at play a little bit)


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