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Old 14th January 2008, 08:58   #16
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Quote:
DirtyDan : ...the transmission, will quickly destroy your drive train, usually the tranny. VERY QUICKLY make that, okay?
DirtyDan : The tranny in one lasted 400K the other lasted just under 200K.
Dan, was it 200K & 400K miles / km - or 200 & 400 miles / km ?
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DirtyDan : I was a test driver for Dana-Spicer, ... In that time I happily destroyed many test vehicles. .
Getting paid to be the devil. One, who's job was to do what shouldn't be done. And being able to (safely) experience what happens (to the truck) when we do what we shouldn't.

Dan, don't I envy you ?

Last edited by condor : 14th January 2008 at 09:08.
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Old 14th January 2008, 10:04   #17
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Default 4WD without center differential will get damaged on hard, dry surfaces

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Originally Posted by tsk1979 View Post
Safari and many modern Off roaders have limited slip diffrential. I think most of these concerns are true for locked diffrentials on pavement.
Consider turning in 2WD mode, the outer wheel turns faster than the inner wheel.
If this can cause diffrential damage in 4WD, it will cause damage in 2WD, but since the diffrentials are able to slip(limited slip) its okay.

however if you have an offroader with locking hubs(eg, old jeeps where you get down and lock the hubs) you will get damage while on pavement.

I guess a seasoned offroader can tell whether the Safari 4WD has locked diffrentials in 4WD mode(the manual says LSD).

In the gypsy its written on the manual that the 4WD High can be used on normal wet roads etc., but 4L should be used only in slush.

Any 4WD system without a center differential will get damaged (transmission windup) if it is driven on dry, hard surfaces in the 4WD mode. Even the LSD (limited slip differential) will not help. The LSD only helps balancing the forces within one axle, not between axles. If 4WD is engaged on wet tarmac, the slippery road will let the wheels turn extra as required to release the transmission windup, and thus the damage is minimised.

The Safari 4WD only has LSD on the front axles, and does not have full-locking differentials (like in the Force Judo/Gurkha).

Locking hubs are a different concept altogether, and not related to differential locks at all. In a 4WD vehicle without hub-locks, the front axle also loads the engine in the 2WD mode. In a vehicle with hub-locks on front axle (the older Gypsies for eg. ), the locking hubs (when unlocked) help reduce the load of the front axle on the engine in 2WD mode.

Hope I have put it in an understandable way .
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Old 14th January 2008, 10:41   #18
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You will not feel the difference on those aspect while driving in the city.

Clutch is hydraulic

Brake is Electronically assisted

And you have power steering.

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Originally Posted by originalamit View Post
A couple of more questions from the driveability point of view:

1) Any difference in the feeling of the clutch and brakes compared to a 2WD?
2) Does the steering feel more harder compared to the 2WD?
If i do go for a safari, it will be 4WD version only but i still need to ensure it is easy to drive in city.

Thanks

Amit

Dan, the manual has special notice "not to run the 4WD on hard and paved surfaces for longer period of time as it will cause expensive damage to the transmission and tyres".

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Originally Posted by DirtyDan View Post
If you run a Safari on dry pavement my best guess is that you will ruin your tranny fast. Safari owners??? Please look it up in your manuals and let us know.
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Old 14th January 2008, 12:31   #19
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Originally Posted by BUSA View Post
Real time AWD are mostly in 2WD mode and shift to AWD when there is loss of traction or when the mechanism senses the requirement.
Not true. Its done differently by manufacturers. CRV might do what you say. BMW and other sporty inclined ones put more power to rear wheels than front ones in normal conditions (but both are powered). Some put all power to rear wheels and AWD takes care when to power the front wheels.

Since a AWD always applies corrections in real time there should not be any problem with this.
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Old 14th January 2008, 14:45   #20
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From the above discussion it appears that unless you have a limited slip center differential which allows different speeds of front and rear axles, 4WD should be used only then you are stuck, or you are driving on slush where there is high probability of getting struck in slush.
On rocky terrain, where there are just big rocks and not much slush, 4WD mode may actually lead to damage?!
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Old 14th January 2008, 19:57   #21
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Quote:
Originally Posted by tsk1979 View Post
From the above discussion it appears that unless you have a limited slip center differential which allows different speeds of front and rear axles, 4WD should be used only then you are stuck, or you are driving on slush where there is high probability of getting struck in slush.
On rocky terrain, where there are just big rocks and not much slush, 4WD mode may actually lead to damage?!
I am not sure what you have in mind when you say "big Rocks". But what it amounts to is that you need to have some slippage on the surface or you will get tranny windup. Friction caused by the difference in speed between the front and rear axles will cook a tranny fast. I have owned many four wheel drive vehicles and I did not baby them. Most of them were pretty robust. I did not run them for any prolonged period on dry pavement in four wheel drive, but a hundred meters here and fifty there never seemed to hurt. It's the heat build up over a prolonged time that wrecks the tranny and drive train. Again, in test I saw trannies cooked at 200k and 400k on 2 vehicles. I was actually supposed to be testing the front axles on the 2 vehicles looking for a supposed factory manufacturing flaw but we kept melting the trannies before we could get a good test on the axles.
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Old 15th January 2008, 15:01   #22
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Originally Posted by CrAzY dRiVeR View Post
What about vehicles with real-time AWD? Any special mechanism to prevent differential damage?

That is the job of the central differntial.
Either Torsen or viscous coupling mostly.
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Old 15th January 2008, 17:22   #23
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Originally Posted by BUSA View Post
Real time AWD are mostly in 2WD mode and shift to AWD when there is loss of traction or when the mechanism senses the requirement.
Like the 'Quattro' mechanism in Audi, you mean? Correct me if I am wrong.
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Old 15th January 2008, 21:51   #24
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What about big army Stalion trucks. I have seen many of them in Delhi. I have seen that they always run in 4x4 mode. Always.
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Old 15th January 2008, 22:53   #25
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Dirty Dan and Blue thunder are right.

Unless your vehicle is equiped with a center differential you should not run your jeep on 4x4 high or low in dry pavement. It will cause what is called as axle windup and eventually destroy the drive line.

This has nothing to do with limited slip or locking differential and has every thing to do with whether your car is a full time or part time 4wd. Safari is a PART TIME 4WD and should not be used in 4x4 mode on road.

You might not notice the difference while travelling in a straight line, but try turning your vehicle at 5 kmph in a U turn with 4x4 on and see how the steering feels. You will be fighting with it even with a power steering. ( and putting strain on the PS pump ) .


With a part time 4wd there are just 2 differentials one in the front axle and the other in the rear axle.

With a full time 4wd there are 3 differentials front axle , rear axle and the transfer case . The transfer case differential is mounted transverse and one side is connected to the front propeller shaft and the other side to the rear propeller shaft.

When you turn your vehicle the front portion of your vehicle describes a bigger circle than the rear portion of your vehicle. However you have one engine running at one speed supplying power to both axles. (if engaged in 4wd mode while turning ) . This difference in speed causes the drive train on the rear/front to twist like a rope being twisted. Which results in damage. The center differential allows for this slip and lets you drive in 4x4 even on dry pavement.


W.r.t to AWD, there are 2 differentials ( front axle and rear axle ) but the center differential is replaced with a hydraulic coupling or slush box. Think of it as a viscosity based differential. That transmits power to both axles and allows them to slip while still supplying power. Any difference in speed is compensated by the slip in the viscous coupling
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Old 16th January 2008, 03:05   #26
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@rrnsss: Spot on dude. Very well explained.
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Old 16th January 2008, 17:51   #27
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Default less body roll with 4WD?

Can you please confirm if the body roll is indeed lesser compared to a 2WD? This is a big thing for me as my kid gets motion sickness and i cant have her throwing up every time i would take out the vehicle...

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Originally Posted by xbox360 View Post
Not sure about ride comfort, but have been told that the 4WD has lesser body roll.
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Old 16th January 2008, 19:32   #28
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Originally Posted by austere_sly View Post
What about big army Stalion trucks. I have seen many of them in Delhi. I have seen that they always run in 4x4 mode. Always.
No, they don,t. They do not have unlockable hubs, so the front wheels keep turning the driveshaft. The driveshaft will not be engaged with the transmission in the TCase in 4x2, ie normal road use.
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Old 16th January 2008, 21:06   #29
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Originally Posted by originalamit View Post
Can you please confirm if the body roll is indeed lesser compared to a 2WD? This is a big thing for me as my kid gets motion sickness and i cant have her throwing up every time i would take out the vehicle...
Sir, if you are going to purchase a 4x4 just for reduced body roll, you will be disappointed. I dont think the difference will be perceptable.
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Old 16th January 2008, 22:17   #30
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When the Tata guys say shift on the fly Bosch Wargner Transfer case, what do they mean?
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