FredTJ

No you're not, if you're in 2WD.
Think about it some.
If you can't figure it out, post up again and I'll explain it




Fred

ovrrdrive

If you're in tune with your truck and have been driving it long enough you can feel it. I know I sure can. There's also a slight drop in fuel mileage too if you track it. I bought my truck new back in December 1994, and before this one I had a brand new 1994 truck and I could feel it in both of them. Some people just aren't observant enough to feel it.

I'll admit there have been a few times where I forgot it and left them locked in for a week or so, but the whole time I was feeling like something was wrong but just couldn't put my finger on it. Every time when I realized it and unlocked them it felt like I added a turbo to the engine...

It's normal, don't worry about it.

MMA_Alex

yeah but its like having weight in the truck, which some of us do in the winter in the form of sandbags. I'm sure it would drop the mileage, but way less noticable than things like the crappy winter blend gas used in the northeast.

Flash319

Please enlighten Fred..............

thook

LEt me take a crack at it.....

Yes, there is "some" resistance. For example, if you have the vehicle jacked up in the front with the hubs locked and in 2wd you will notice a difference if you turn a wheel or the driveshaft by hand as opposed to turning the same with the hubs unlocked. Why? Because you are turning gears that are turning mass and weight. BUT, this is nothing compared to the power of the engine turning those same components. (Don't forget the human mind is at play here. If it's looking for something, it very well may find it....even if it's not really there.) To really pinpoint how much difference there is...between driving in 2wd with hubs locked or not.....you would have to have an extremely controlled enviroment in which to measure it. Think about that. I did almost all the way in to town today....while also pulling over a few times to lock and unlock to check myself. I really couldn't notice any difference in the feel or power. If there actually is a difference for anyone else, it should be neglegible.....a no concern. I say that because a good portion of the group has that experience. Having the hubs locked should not create a condition that would compromise power and mileage in any significant way. If it is, and one is wondering why when someone is not having the same problem, you have to think that maybe someone else may have newer or better lubed cv's, u-joints, transfer case, diff gears, bearings, different tires, and on and on. All those parts are coasting and should be coasting freely. Once they are moving, they should be really moving themselves through momentum......which is to say coasting.

It will not be the same for 4wd. With 4wd, the engine is then also transferring power to the front drive components and wheels to push the vehicle. The real resistance comes not from the components, though......in 2wd or 4wd. It comes from making contact with the ground and power (kinetic energy) begin transferred to it. 2wd = two transference points....4wd = 4. You've doubled the power loss. If you were not touching the ground, you're mileage would be a lot better.....even in 4wd.

I hoped I explained that well enough.

82yota

I'm going to have to say that having the hubs locked or unlocked plays a part in mpg and power. Even tonight I noticed it. I was pulling my snowmachine on a trailer to town and back and had a hill to climb. I have never ever noticed that my diesel would drop in speed on any hills but it did drop tonight with the trailer and snowmachine on with the hubs locked. That was on the way to town. On the way back I had them unlocked and did not lose any speed. You notice it driving around town and on the highway. And it is all turning and using power to turn whether you are in 2wd or 4wd with the hubs locked. All that stuff up front still needs to be pushed to turn. There is preload on the bearings. The oil is thick. Grease in the joints. All that stuff has to be pushed along and it will put a drag on the truck. I do not notice it so much with the new truck and the diesel as its got power but I sure can notice it in my 82 with the 22R. Not a whole pile but it definately is there. Oh and sorry for typing so much all the time. I just get going and it really takes me no time to type up a storm.

FredTJ

If the wheels were not touching the ground your mileage would suck...
You'd burn a tank of gas and would not have moved an inch.
Sort of like idling at a stop light, your mileage sucks then.





Fred

thook

Okay...okay. You know what I mean.

FredTJ

Yeah, just ribbing, however the main reason that the "mileage" would go up with the wheels off the ground is because the engine wouldn't be producing hardly any HP regardless of the rpm that you ran it at.




Fred

thook

Yeah, I know.

What's this about horsepower then? How is it "not" being produced? I thought it was produced during combustion relative to displacement and blah, blah, blah. Please explain...

FredTJ

Sure, some HP is produced, just enough to turn everything to turn the wheels off the ground, but no more HP than that.
The HP (and torque) rating for the engine is the MAXIMUM that it will produce, not what it always produces.
Reduce the load and the HP production reduces also.
Think about it (not even the technical part).
HP takes energy. Even given amount of gas contains x amount of energy.
The only way the engine can run longer (time wise here with the wheels off the ground) on the a given amount of gas (say a full tank) is to produce less HP.
If it were producing the same HP as when the wheels are on the ground and struggling to pull a 2 ton trailer up a hill, even if the extra HP was just wasted, thrown away as heat or something, then the amount of time that the engine would run (at any given rpm) on a tank of gas would be the same, right ?
But it's not. You can run the engine a lot longer with the wheels off the ground, that is you're burning less gas and therefore producing less HP (and torque).
The gasoline engine is actually a "variable HP (and torque)" producer.




Fred

thook

Oh, okay. Thanks for clarifying that.

Diesel_Freak

Sure, there's drag, what I mean is tha tout of 4wd there is no connection between the front drivetrain and the motor, menaing that even hubs locked in but in 2wd you're not turning the wheels with the motor from the t-case side (I relaize you're still using the motor to push the wheels along the road and therefore turn the D-shaft). It has not in my experience been anough to really feel too much, and certainly not what the guy who started this is experiencing.

thook

Haha...I even asked my wife last night (without her knowing about this thread) if whenever she drove my vehicle with the hubs still locked did she ever notice power loss and such. "NOPE". She wouldn't even know to look for something like that, either. I'm not saying anything contradictory to those who experience such, I'm just wondering now why others do when I and others don't.

BTW, just to qualify her testimony, she's not the unobservant type. Plus, she used to work in a garage and tune her '55 Chevy a couple decades ago. So, she's not completely ignorant with vehicles.

82yota

For me it could be that the only time I drive with them locked is in the winter and the gear oil when shes good and cold out is pretty much just sludge. But it still uses up some power to turn that whole front end. And whether its in 2wd or 4wd you are either putting all the power to the back wheels to shove the front along or you are using some to pull the front and some on the back. Shouldn't make much of a difference there. At least it doesn't for me. I've never tried it locked in the summer so I don't know what it feels like without sludgy thick oil in it.

thook

Hey, aren't there different weight gear oils for running in extreme colds?

82yota

There are synthetics but don't need to run them. Never had a problem with regular oils in anything we have around here other than they slow you down till they warm up. They can be a pain when its -40 but they warm up. I'll have to try the hubs locked this summer when its warm.