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Old 9th February 2012, 22:51   #121
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Originally Posted by Sutripta
Hi,
Thought the Safari LSD was clutch based.
No idea about the Endeavours LSD, but a Torsen is expensive.

Regards
Sutripta
Sorry my mistake. I thought I read somewhere about a torsen on the Safari. I know for a fact that the Endeavour has a Torsen though. Which is good
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Old 10th February 2012, 10:00   #122
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Originally Posted by Endeavour333

Sorry my mistake. I thought I read somewhere about a torsen on the Safari. I know for a fact that the Endeavour has a Torsen though. Which is good
Why do you think it is good? Isn't clutch based LSD better, it won't give up when one Tyre goes up in air.
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Old 10th February 2012, 19:11   #123
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Originally Posted by Samurai
Why do you think it is good? Isn't clutch based LSD better, it won't give up when one Tyre goes up in air.
I could be wrong but clutch based LSDs don't transfer very much torque to the other wheels do they? Also they require plenty of wheelspin to actually work. Torsens work with minimal wheelspin. I have always wanted to compare the two types of diffs. I have read up more on torsens though.

I would be interested to know why you think clutch based LSDs are better because I am in the torsen camp right now.

There are various types and grades of clutch based LSDs and torsens that have preloads, etc but for this argument let us just consider the grade of LSDs available on Indian SUVs? Like the clutch pack on the pajero or safari vs torsen on the Endeavour? If clutch packs are better why do Prados and Land cruisers have Torsens?

Not trying to pick a fight or something, just throwing up some questions for the sake of this comparison.
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Old 10th February 2012, 20:40   #124
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Default Torsen

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Originally Posted by Endeavour333 View Post
I could be wrong but clutch based LSDs don't transfer very much torque to the other wheels do they? Also they require plenty of wheelspin to actually work. Torsens work with minimal wheelspin. I have always wanted to compare the two types of diffs. I have read up more on torsens though.

I would be interested to know why you think clutch based LSDs are better because I am in the torsen camp right now.

There are various types and grades of clutch based LSDs and torsens that have preloads, etc but for this argument let us just consider the grade of LSDs available on Indian SUVs? Like the clutch pack on the pajero or safari vs torsen on the Endeavour? If clutch packs are better why do Prados and Land cruisers have Torsens?

Not trying to pick a fight or something, just throwing up some questions for the sake of this comparison.
Hi Vishnu,

I'll answer in points

1) Clutch Packs are better because they give better traction. If the Clutch Pack is adjusted, then you can have an almost locker-like effect.

The clutch packs work better in slower speeds, where as the torsen normally require a higher speed (i.e wheel speed mismatch to engage) in case of a higher wheel speed (mismatch) the Clutch Pack LSD will slip out and act like an open diff.

2) The Torsens are more expensive, but show lesser wear and tear, but again vulnerable to shock load, hence the clutch pack LSD are still used as OEM on off-highway equipment.

Regards,

Arka
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Old 11th February 2012, 08:05   #125
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Originally Posted by ex670c

Hi Vishnu,

I'll answer in points

Regards,

Arka
Thanks for that info Arka. I was under the impression that clutch packs require plenty of wheelspin to heat up the clutch so that it will expand (or something like that) and put pressure on the other plate causing torque transfer.

I just read up on how they work properly. Seems to make sense how they provide more traction off road especially in low traction or wheel in air situations. Here is the explanation and link:

http://auto.howstuffworks.com/differential4.htm

"This type of LSD has all of the same components as an open differential, but it adds a spring pack and a set of clutches. Some of these have a cone clutch that is just like the synchronizers in a manual transmission.
The spring pack pushes the side gears against the clutches, which are attached to the cage. Both side gears spin with the cage when both wheels are moving at the same speed, and the clutches aren't really needed -- the only time the clutches step in is when something happens to make one wheel spin faster than the other, as in a turn. The clutches fight this behavior, wanting both wheels to go the same speed. If one wheel wants to spin faster than the other, it must first overpower the clutch. The stiffness of the springs combined with the friction of the clutch determine how much torque it takes to overpower it.
Getting back to the situation in which one drive wheel is on the ice and the other one has good traction: With this limited slip differential, even though the wheel on the ice is not able to transmit much torque to the ground, the other wheel will still get the torque it needs to move. The torque supplied to the wheel not on the ice is equal to the amount of torque it takes to overpower the clutches. The result is that you can move forward, although still not with the full power of your car."

In STOCK configuration (in a pajero) will the springs transfer a significant amount of torque to the opposing wheel?

For torsens I understand that difference in wheel speed is required for torque transfer to happen. I suppose each type performs better in different situations.

For torsens a throttle while braking technique can be used to transfer a significant amount of torque to the other wheel. Here is how it's done: bring both wheels to a stop, apply brakes (normal brakes or hand brake since I have torsen only on rear axle?), gradually apply throttle while releasing the brake, this will make the torsen transfer 3 to 4 times the torque it takes to overcome the braking force to the wheel that has grip.

Hummers and even the Humvee have torsens on both from and rear axles. They use the throttle brake technique quite often to get out of 2 wheels in the air or 2 wheels spinning situations.

In low traction situation like soft sand or slush the clutch probably provides enough resistance for the diff to act like a locker correct? How does a torsen perform in this scenario?

I now have more respect for clutch based LSDs

Last edited by Endeavour333 : 11th February 2012 at 08:14.
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Old 11th February 2012, 13:18   #126
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Default Re: RWD vs. FWD vs. AWD

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Originally Posted by SS-Traveller View Post
A comparison summary of the various drive systems.
Thanks for this valuable information, real helpful in deciding on my next vehicle
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Old 11th February 2012, 21:17   #127
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Default Re: Torsen

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Originally Posted by ex670c View Post
1)If the Clutch Pack is adjusted, then you can have an almost locker-like effect.
The adjustment is a vitally important, often overlooked point.
These clutches do wear out, and so to work properly, need fairly regular adjustment.

Regards
Sutripta
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Old 11th February 2012, 22:23   #128
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Default Re: Driving all four wheels: how is it done?

^^ Dada, Arka, how is the setting done? What are the things to be kept in mind while doing the setting? What does the service procedure suggest, parts to be checked, replaced etc.?

I have used it (assembled) but never personally seen the work being done, so asking.

Spike
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Old 13th February 2012, 10:31   #129
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Default Re: Driving all four wheels: how is it done?

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Originally Posted by SPIKE ARRESTOR View Post
^^ Dada, Arka, how is the setting done? What are the things to be kept in mind while doing the setting? What does the service procedure suggest, parts to be checked, replaced etc.?

I have used it (assembled) but never personally seen the work being done, so asking.
Hi Spike,

Most LSD come with a service pack which includes the Clutch Plates & Washers or in case of a conical clutch/wedge, the wedges and Coil Springs are included.

How to setup a LSD tight (more traction)
1) increase the number of clutch plates
2) Use thicker Clutch Plates
3) In case of the Conical Clutch LSD, stiffer Springs can be used for better grip.

Regards,

Arka
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Old 13th February 2012, 12:45   #130
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Default Re: Driving all four wheels: how is it done?

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Originally Posted by ex670c View Post
Hi Spike,

How to setup a LSD tight (more traction)
1) increase the number of clutch plates
2) Use thicker Clutch Plates

Arka
Hi Arka,

It is always a pleasure to read your comments, I am postingt the pics of XUV 4x4 system. pls comment to what extent we can use it in offroading. how effective it will be in sand, mud, dunes & steep climbs. Here I am not talking about any serious kind of offroading.

Driving all four wheels: how is it done?-sam_0578.jpg

Driving all four wheels: how is it done?-sam_0360.jpg

Driving all four wheels: how is it done?-sam_0568.jpg

secondly is it possible to change the clutch part in XUV (highlighted with circle) with a transfercase, matching the same gear ratio; offcourse after warranty period. And also what will happen if the gear ratio of front and rear axle is different in offroading condition, considering that front on normal gear ratio & rear at lower gear ratio.

regards,

Alok
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Old 13th February 2012, 15:50   #131
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Default Xuv500 4wd

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Originally Posted by Crazy4Power View Post
Hi Arka,

It is always a pleasure to read your comments, I am postingt the pics of XUV 4x4 system. pls comment to what extent we can use it in offroading. how effective it will be in sand, mud, dunes & steep climbs. Here I am not talking about any serious kind of offroading.

Attachment 887118

Attachment 887119

Attachment 887120

secondly is it possible to change the clutch part in XUV (highlighted with circle) with a transfercase, matching the same gear ratio; offcourse after warranty period. And also what will happen if the gear ratio of front and rear axle is different in offroading condition, considering that front on normal gear ratio & rear at lower gear ratio.
Hi Alok,

Thanks for the interesting pics. My observation from the pics

Pic#1.
The transverse mounted engine drives the Cluth Assy and Gear Box which drives a large (almost 4:1) Helical Gear mounted on a Hypoid Gear Assy (Spider Gears) which provide for the Differential Action.

The RHS Drive Shaft has a Crown & Pinion gear assy to take drive off to the Rear Differential.


Pic#3.
The Crown & Pinion Assy connects to the rear differential, through a Clutch Pack, this indicates the vehicle is not a real AWD, and the Rear Differential will engage when there is sufficient slippage leading to the Diff Assy oil heating up and expanding the Clutch plates; thereby engaging the Rear Diff & Axles.

If the Clutch Assy was not fitted on the rear differential pinion input, the vehicle will be a AWD. But this kind of AWD (hypothetically will be unsuitable for Road Use) with the Rear Diff running off a scavenged drive Or if there is a selector mechanism it will become FWD with 4WD.

If the system is efficient enough and generates enough torque and if it can reach the wheel, definitely the vehicle can move over sand, mud, dunes & steep climbs.

Normally in a vehicle the Front Wheel are slightly faster than the rear wheels, if the rear wheels are considerably slower then the front can Drag the Rear Wheels.

If the Rear Wheels have a lower gearing then you will have to use taller tyres rear to balance front & rear wheel speeds.

Look a 4WD Tractors, the Rear is 28" Rim, but the Front is 16" and hence the diff-ratio in the front is compensated for the Tyre OD.

Regards,

Arka
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Old 13th February 2012, 17:01   #132
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Default Re: Xuv500 4wd

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Originally Posted by ex670c View Post
Hi Alok,

Or if there is a selector mechanism it will become FWD with 4WD.

If the system is efficient enough and generates enough torque and if it can reach the wheel, definitely the vehicle can move over sand, mud, dunes & steep climbs.
Regards,

Arka
With your explanation I can understand this mechanism better.

YES they have AWD lock selector button, which can be activated to forcibly bring the car to AWD. I think this is a big plus to avoid the unnecessary clutch slippage.

With the current setup it looks front & rear will be running on same gear ratio and the torque split will be 50:50 in AWD lock mode. With 320 KN of torque it should be able to handle any tough terrain. My only concern is whether these axles and clutch pack can handle continuous running for longer period in offroad conditions ?

Thanks!
Alok
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Old 13th February 2012, 18:42   #133
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Quote:
Originally Posted by ex670c
Pic#3.
The Crown & Pinion Assy connects to the rear differential, through a Clutch Pack, this indicates the vehicle is not a real AWD, and the Rear Differential will engage when there is sufficient slippage leading to the Diff Assy oil heating up and expanding the Clutch plates; thereby engaging the Rear Diff & Axles.

Regards,

Arka
Arka this is the kind of LSD I had associated with a "clutch pack" LSD. Like you said above, I thought they required a lot of wheel speed difference to engage and transfer torque.

So there are 3 types of clutch pack LSDs?
1) conical
2) normal
(both conical and normal are engaged at all times acting like a locker until wheel speed differential forces are large enough to slip the clutch)
3) oil based clutch pack LSD like in the XUV: high wheel speed differential required to heat up oil to make clutch places press against each other to transfer torque.

Please correct me if I'm wrong.

How do I differentiate between the types when I look at the spec sheet of a car?
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Old 13th February 2012, 19:14   #134
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Default Re: Driving all four wheels: how is it done?

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Originally Posted by ex670c View Post
Pic#3.
The Crown & Pinion Assy connects to the rear differential, through a Clutch Pack, this indicates the vehicle is not a real AWD, and the Rear Differential will engage when there is sufficient slippage leading to the Diff Assy oil heating up and expanding the Clutch plates; thereby engaging the Rear Diff & Axles.
Quote:
Originally Posted by Endeavour333 View Post
3) oil based clutch pack LSD like in the XUV: high wheel speed differential required to heat up oil to make clutch places press against each other to transfer torque.
Hi Vishnu,

The 3rd Type is known as the Viscous Coupling type and IIRC is not directly used in the differential.

Regards,

Arka
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Old 13th February 2012, 20:15   #135
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Default Re: Driving all four wheels: how is it done?

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Originally Posted by ex670c View Post
The clutch packs work better in slower speeds, where as the torsen normally require a higher speed (i.e wheel speed mismatch to engage)
I think Torsens are always 'engaged'.

Quote:
Originally Posted by SPIKE ARRESTOR View Post
^^ Dada, Arka, how is the setting done? What are the things to be kept in mind while doing the setting? What does the service procedure suggest, parts to be checked, replaced etc.?
Check breakaway torque, adjust preload.
Anyone with a Safari 4x4 manual?

Regards
Sutripta
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