Probably dumb but...First vehicle with 4wd I have ever had. Coming into work this morning, probably needed 4wd in the development. Once I got to the "main" raod, parts were wet, parts were snow covered and thick, some were packed down and some were even clear and dry. 4wd probably would help in most cases but would any type of damage be done when driving on the wet or dry pavement with 4wd? Should you go back and fourth between 4wd hi and 2wd or just keep in 4wd or only put in if stuck??????
4WD Question
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me, i tend to leave it in 2wd and only go to 4hi when i think i might lose all traction. I just slow down and 2wd works fine.
I spent most of this last snow storm in 2wd. Only really put it in 4wd when i was playing in the deeper drifts.
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You should only use 4wd when one of your wheels can slip. The reason you don't use it on hard pavement is because the gear rations aren't exactly the same in the front and rear. Since they aren't exact the tires are going to go a very slightly different speeds. If you run it on dry pavement or a surface that there is no room for slip then the gears and axles will eventually bind and in the worse case break.
That said, if you are going straight for short patches of clear road, and there is snow on either side i usually leave it in 4wheel. When going around corners is when you have the greatest difference in gear ratios so things tend to bind quicker going around a corner.
I can pretty well shift on the fly with mine by pushing in the clutch and pulling on the lever a couple times, so I just put mine in and out when needed.
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Quote from "DieselCj"
You should only use 4wd when one of your wheels can slip. The reason you don't use it on hard pavement is because the gear rations aren't exactly the same in the front and rear.
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???Never heard that before.
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I think the gears are the same, but if you run tire pressure like it says in the manual (YJ), you have 28 in the front, and 32 in the back. That would change the ratios between front and back. I have wondered (since I got this thing) why? why would they want you to do that? Some kind of patch maybe, for handling?
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Quote from "KnuckleHead"
???
???Never heard that before.
Some vehicles might have 4.10 in one end and 4.11 in the other, or 3.54 and 3.55. It's a small enough difference it's really not noticeable.
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I could be off on this one, but say you have 4.11's in the front and 4.10's in the rear. So every time your front tires rotate 411 times, your rear tires will rotate 410 times. The gearing is constant, no matter if you are turning or going straight. I have always believed that the binding while turning is due to the inside tires traveling a shorter distance than the outside tires of the turn. I could be wrong...
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Quote from "vbquick1"
I could be off on this one, but say you have 4.11's in the front and 4.10's in the rear. So every time your front tires rotate 411 times, your rear tires will rotate 410 times. The gearing is constant, no matter if you are turning or going straight. I have always believed that the binding while turning is due to the inside tires traveling a shorter distance than the outside tires of the turn. I could be wrong...
I believe you are correct.
My point was just that there are certain vehicles that come/came with slightly mis-matched gear ratios and that it is really insignificant in the real world.
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Quote from "vbquick1"
I could be off on this one, but say you have 4.11's in the front and 4.10's in the rear. So every time your front tires rotate 411 times, your rear tires will rotate 410 times. The gearing is constant, no matter if you are turning or going straight. I have always believed that the binding while turning is due to the inside tires traveling a shorter distance than the outside tires of the turn. I could be wrong...
your close. the binding is the front and rear spinning at diffrent speeds while turning sharp. the inside tires will spin at diffrent speeds, but unless you have a tight locker or a spool there wont be any binding from it.
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Ive got 411 in the front and 409 in the back....I guess Drivetrain direct used a different gear manufacurer.
Anyway mine works well. -
You are allowed some difference. Remember that those ratios are rounded up or down to 3 significant figures anyway. So that puts some error in automatically.
And a bit of gear trivia:
The reason why the ratios are never a whole number like 4:1, 3:1 or whatever is so the same teeth on the ring gear don't always touch the same teeth on the pinion. Having the ratios a wierd number like 4.09, 3.73, 5.32... evens out the wear on the gears in case one of the teeth develops a bur or imperfection.
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That's interesting, Silmer, but there is still the burning question; why do we need (or want) the ratio to be different front/back?
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your close. the binding is the front and rear spinning at diffrent speeds while turning sharp. the inside tires will spin at diffrent speeds, but unless you have a tight locker or a spool there wont be any binding from it.
I must disagree. Like I stated above, if your gearing is slightly different (ie 4.11 front to 4.09 rear) than for every 411 times your front tires rotate your rear tires will come up two rotations short. So lets go a little further with that using basic math. If you are running 33 in tires the circumference of the tire is (33 x 3.14 =) 103.62 inches. So for every (411 x 103.62 inches= 42,587.82 inches / 12 = ) 3548.985 ft that you travel with the front tires your rear tires will travel 3531.715 ft. That is a difference of 17.27 ft over 2/3's of a mile. This mean that if you front tires are traveling a 5 mph, your rear tires are traveling at 4.98 mph. I am not a physics professor, but I dont think that is enough.
I have changed my opinion on the bucking though. I agree with Chris in that if you are not using a locker the distance traveled for the inside and outside tires would not really make a difference. I always take lockers for granted cause most of us run them.
Due to the slow speeds that this situation occurs at, weight shift is probably not a factor. I think the reason this occurs is a combination of the difference in directional forces applied to the vehicle. This is the result of the short wheel base and the front wheels being turned in one direction and the rear wheels facing another direction. This is compounded by the fact that the front and rear diffs are sending power every which way because of the constant weight shift from one tire to another after force is applied to any of the other tires. So to be a lil clearer, during a sharp turn the front tires are producing force in a direction like this \---\ and the rear tires are producing force in a direction like this |---| causing the vehicle to "buck".
So thats my new opinion....LoL
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Sean, in a sharp turn (like in a parking lot), the front set of wheels travel a larger radius than the rear set. So that would cause your springs or suspension to wind up then release if you have the trasfer case engaged, causing the bucking. Right?
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LoL
Yup thats right! See what happens when math takes over my mind! -
Quote from "Simon"
That's interesting, Silmer, but there is still the burning question; why do we need (or want) the ratio to be different front/back?
You don't necessarily _want_ the ratio to be different...in fact you want them as close as possible. The reason you find slight variations is due to the size of the gears and hence the number of teeth on the ring and pinion. If you look at a r/p set for a D30 it is a good bit smaller than one for a D44...when changing the ratio you're putting a larger number of teeth on the ring and a smaller number on the pinion. Due to the size constraints (they need to keep teeth a decent size for strength) manufacturers will use different numbers of teeth to acheive a similar ratio, for example your rear axle might have 41/9=4.55 while your front is 32/7=4.57. This slight mismatch is fine as long as there's some slippage to account for the difference.
The other reason for only using 4wd on a surface where slippage can occur, as chris alluded to, is the difference in the distance traveled between wheels...left to right isn't a problem as we've got a differential to take care of this. The issue is that the front and rear axles are locked together and when taking a turn your front axle travels further than the rear...if the road surface doesn't allow for slippage front to rear after awhile this binding will increase until it finds the weakest link in the system which could be as simple as your tires scrubbing or as bad as a stretched/broken tcase chain or broken ujoint. This is why on a fulltime 4wd or AWD system you have some type of viscous coupling...it still provides power to both ends but allows for a bit of slippage.
--Ian
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I believe all this is also the cause for the transfer case to be stuck in 4wd until you back up a little to "unwind" the build up gear tension. You can also do this by going forward slowly while swirving back and fourth. The swirving causes a "load and unload" situation with the front wheels which will also release some gear tension.
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Thank you, Ian, and Slimer!
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