why four wheel drive

is it normal for my truck to be hard to turn in four wheel drive. which ever way i try to turn the steeering wheel wants to pull the other way. also how fast do u have to be going when u let off the accelerater to take
it out of four wheel drive. auto locking hubs of course
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What kind of terrain are you on?
Bill
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wrote:

info. yes, it is normal to be more difficult to turn in 4wd.
-Bret
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also you may have a limited slip differential. That would make it try to go straight ahead when turning. keep it though, just use it. old john

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If you turn your wheels slightly in one direction, your tires will track paths of two large circles, one inside the other -- even though both tires are angled equally in the same direction, they are tracking different diameter circles. The inner tire will be trying to go less into the turn, that is, straighter but this reaction is not noticeable.
If you turn your wheels fully in one direction, your tires will track paths of two smaller circles, one still inside the other. The inner tire will be working harder to go less into the turn and this reaction is more noticeable (inner tire shuddering, skipping, squealing, etc. more than the outer tire) because of the smaller turning circles tracked. It is even more evident in 4x4 mode.

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This is not true. The inner tire is angles more then the outer tire. This is called the Ackerman Affect http://www.rctek.com/handling/ackerman_steering_principle.html

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That link doesn't take into effect 4wd. If both tires were trying to turn the same rate, the extra angle will make no difference. See title of post... He's in 4wd.

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No crap. I was addressing the post just before mine.
When in 4WD with a locked transfer case, then you have a problem with the distance traveled by the front tires vs. the rear.

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I wasn't even considering the rear tires in my reply but you do bring up an interesting point with the front-rear tires in 4WD locked TC. Nevertheless, the original poster did not specify what vehicle he was referring to, hence, it was unknown how much Ackerman, if any, he had.

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Must vehicles I know about have a thing called a differential that allows the inside tire to rotate slower then the outside tire.

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For rear wheels, yes, but the original post was talking about his "steering wheel(s)."

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Franko wrote:

All vehicles with a front driving axle also have a differential in the front axle. Some 4x4's have a differential in the transfer case to allow for differences in speed between the front and rear axles, others use a viscous coupling, which achieves the same thing...and still others use clutch packs to achieve this.
Ian
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So, back to the original post, "is it normal for my truck to be hard to turn in four wheel drive..." and answer his question.

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Franko wrote:

Why? I was simply commenting on your comment. I don't remember there being any rule that says I have to respond to the OP.
In your original answer to the post, you pretty much completely missed what he was asking. You started talking about the relative circles that an inner and an outer wheel will make when turning left or right. Steering linkage geometry takes care of what you are describing. Differentials are designed to take care of the different "speeds" the wheels are traveling, the steering linkage geometry takes care of the different "size" circles the tires are going around. One is about angles, the other about relative speeds.
If a four wheel drive vehicle is in the 4x4 mode that is locked from front to rear....you are going to experience "crowhopping" which is what the original poster is complaining about. There isn't anything you can do about that...it's normal. If you have some sort of differential action in the t/case, "crowhopping" will be either non-existant, or very minor.
Ian
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OK, glad too see I was not the only one who felt like this should not have been that difficult.
Thanks for pulling together a final response.

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I'll bet he put more effort into his answer than the "cut and paste" you posted on the "Ackerman Affect..."

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Heheheheh, no need to get your knickers in a knot fellas. Please don't get offended -- just trying to stay on topic with the original question which, incidentally, was followed by a comment that (paraphrasing) regardless of which way he turned the steering wheel, it still wants to pull the other way. Steering linkages (i.e., Pitman arm angles) do take care of, but obviously does not compensate for all of what was causing his observations, and likewise for differentials. Otherwise, he wouldn't be having those "hopping" symptoms in the first place (???); /QED. Hence my descriptions. So, in answer to his question, "Yes, it's more normal for vehicles with 'dumb' steering systems." I was surprised nobody added 4-wheel steering...
Thanks DWB, that was off the top of my head trying to remember my professor's descriptions in college 27 years ago -- he predicted 4-wheel steering's main use would be for ease of parking and maneuvering his boat trailer.

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Are you using 4wd on the pavement or a hard surface? It's only for low traction surfaces, where the tires can slip a little... otherwise, you can damage your transfer case by using 4wd with no wheel slip.... YMMV
mac
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