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Old 27th February 2009, 16:26   #31
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Indian Jeeps - Mahindras or the CJ3B Jeep I have can safetly be driven in 4WD whenever off road on soft ground. Once you hit terra firma shift back to 2 WD.

It happened with me once - I had got so used to driving full time 4 WD vehicle that shifting into 4x4 was not in my habit ever.

Nissan Middle East had given me a Nissan Patrol 2008 model which they were testing in 2005 equipped with a new gearbox and transfer case aimed at the Middle east markets. I stopped to deflate the tyres to 12 psi and continued towards the dune. The vehicle started pulling in the sand and got stuck. I thought of everything else and then remembered - of course this is not a Toyota, got to engage 4 WD !
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Old 27th February 2009, 21:18   #32
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Originally Posted by desertfox View Post
There is a lot of myth and misunderstandings that go with the Indian aversion to driving in 4WD i.e. with the 4x4 drive system engaged.

Why shouldn't you drive in 4WD when your vehicle has a 4 WD system in it, it is there for you to negotiate tricky terrain, but the general syndrome is it is some kind of a monster, you must disengage as soon as an obtacle like some soft sand or a mud pool has been crossed.
I just logged in now and stared at this statement in disbelief, and then it dawned on me that your experience is mostly on full-time 4WD which have center diff with limited slip. Please don't attempt this on Indian 4WDs, none of them have central diff.

I have already mentioned this in post #12 about the fulltime 4WD with center LSD:
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My Grand Vitara is mostly in 4H (with center LSD), which I use for street/highway driving. If I want the GV to go offroad, I go 4L then.
But I would never try this in my Mahindra CJ340 since it doesn't have center LSD.

Therefore it has nothing to do with Indian aversion or Indian misunderstanding or myth. It has to do with the fact that we don't have center LSD on Indian 4WD vehicles.
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Old 27th February 2009, 22:17   #33
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You good folks do realize that what works for a Gypsy / MM may not necessarily work for a Safari, right? ....
A VERY important. Infact, even clubbing a Gypsy/MM together may also not be right. Essentially, what works for one 4x4 may not work for another 4x4.

For example, IIRC, a MM's 4H ratio does NOT do any reduction/torque multiplication (please confirm or rectify ) where as in a Gypsy the 4H does a reduction/t-m of 1.409:1

This aspect also would change the equation of using 4H or 4L in various conditions & various vehicles -- depending on how the ratios are setup.

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Originally Posted by vinod_nookala View Post
...4wd H can be good for high powered engines in sandy conditions. Gypsy King does wonderfully in 4wd high on sand. ......
Though my experience of sand off-roading is just 10-20 minutes or so, I would tend to believe what you mention above. A combination of light weight + early availability of momentum in 4H.

For me (especially if it is aknown terrain) most of the times it is 2WD followed by 4H and then as last option 4L. Most of the times this is just to test my vehicles limits & my skills.

However, it was not the case earlier and only when I have got comfortable with the machine & with each passing OTR that I did, this is what I have started following and have become comfortable with it.

If this means getting stuck in 2WD/4H, then so be it -- it is fun, an opportunity to learn & all part and parcel of off-roading

At the end of the day, engage whatever you feel comfortable with that time and that day -- that is most important.
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Old 27th February 2009, 23:57   #34
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Originally Posted by khan_sultan View Post
For example, IIRC, a MM's 4H ratio does NOT do any reduction/torque multiplication (please confirm or rectify ) where as in a Gypsy the 4H does a reduction/t-m of 1.409:1
Wow, didn't know that about the Gypsy. The 2nd in 4H in Jeep is too fast for forest/hill offroading, good for trail driving or sand driving though.
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Old 28th February 2009, 09:34   #35
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Originally Posted by khan_sultan View Post
Though my experience of sand off-roading is just 10-20 minutes or so, I would tend to believe what you mention above. A combination of light weight + early availability of momentum in 4H.
Looks like you need to make it to the TPC09. You will have more than your share of sand. But the vehicles need to be in top shape as the terrain is very demanding!

Try and get your Gypsy too!

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Originally Posted by Samurai View Post
The 2nd in 4H in Jeep is too fast for forest/hill offroading, good for trail driving or sand driving though.

I found 3 low good for sand driving..but i tend to agree that most people do it in 2 low as it gives them a sense of control!

Cheers
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Old 28th February 2009, 12:16   #36
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Originally Posted by khan_sultan View Post
A VERY important. Infact, even clubbing a Gypsy/MM together may also not be right. Essentially, what works for one 4x4 may not work for another 4x4. .
I fullty Agree with you on this matter. We are essentially a Jeep lovers group but now with the new members joining in we have started to experience Gypsys. There gearing ratio is very different.


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Originally Posted by khan_sultan View Post
Though my experience of sand off-roading is just 10-20 minutes or so, I would tend to believe what you mention above. A combination of light weight + early availability of momentum in 4H.
Again the momentum for the sand helps you go on lower gears and anytime you get stuck the 4L is always available to pull you out. Most fun is to be on 2x4 or 4x4 H 3rd and go for the round spins in sands with momentum, the way the Jeep slides is amazing.

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Originally Posted by khan_sultan View Post
For me (especially if it is aknown terrain) most of the times it is 2WD followed by 4H and then as last option 4L. Most of the times this is just to test my vehicles limits & my skills.

If this means getting stuck in 2WD/4H, then so be it -- it is fun, an opportunity to learn & all part and parcel of off-roading
No fun without getting stuck in offroading. Unless we try on lower gears we will never learn the skill of negotiating the Jeeps in various situation. The fun of offroading lies in Trying new things, getting stuck and recovering stuck vechiles. (But not to undermine the importance of safety)

Great Shanawaz !!! for your views I was thinking we at TBHP have extremely cautious drivers.
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Old 28th February 2009, 12:52   #37
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Originally Posted by Samurai View Post
To be honest, I don't understand the purpose of 4H in offroading, as in climbing, crawling, descending, etc.
Sometimes just torque doesn't help. You need momentum too, which is where the 4H gears come in.

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Originally Posted by khan_sultan View Post
For me (especially if it is aknown terrain) most of the times it is 2WD followed by 4H and then as last option 4L. Most of the times this is just to test my vehicles limits & my skills.

If this means getting stuck in 2WD/4H, then so be it -- it is fun, an opportunity to learn & all part and parcel of off-roading
Well said Shahnawaz. Its actually a part of getting to know your vehicle intimately. How it behaves in different terrain. How the tyres respond. Where do you need torque and where do you need more momentum. Watching closely and choosing the right tool to get you out, that to me is offroading skill.

As one doesn't know the full context of Mr. Dhabar's advice on extensive use of 4L it may not be fair to quote him. In all probability his advice applied to a particular type of terrain encountered on the GE's.

Its more fun to graduate through your gear options to the 4L ratios as a last resort. Let the terrain dictate what gear you use and whether its torque alone or momentum or a combination of both which is needed to get you out.

Last edited by DKG : 28th February 2009 at 13:00.
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Old 28th February 2009, 12:58   #38
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Dear Sharath - thank you for mentioning my previous posts. Feels good. The essense is to prevent what is known as "driveline windup" which is bound to happen if you drive in 4WD on hard surfaces as the terrain does not slip beneath the tyres. For this reason, if my memory is correct, I know of a vehicle which has a very small difference in the axle ratio on the front axle with respect to what it has on the rear axle (let me check again). The dynamic rolling radius of the front to rear tyres also varies very minutely due to various factors of steering geometry. For finding out all this you have to dig deep into suspension system design and then burn the midlight oil on detailed layouts, read and read and digest and digest information again and again. It's a never ending process.

Best regards,

Behram Dhabhar
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Old 28th February 2009, 13:20   #39
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Examples of what Behram's said are at :

Crossover SUV Rear Axle Gear Ratios

See a post at Different front and back axle ratios? - Diesel Power Forums at Diesel Power Magazine

Quote

All 4x4 light trucks (1 ton and under) have the 'same' ratio in the front and back from the factory. The reason for different ratios, like 4.09 and 4.10 is the difference in axles and tooth combinations for those axles. Every GM that has a Dana 44 front axle and GM rear axle has different ratios due only to design differences in the differentials (factory differentials that is).

Example: Typical 1/2 ton GM, 10 bolt, 8.5" rear axle and Dana 44 front axle. The 8.5" 10 bolt (used in cars and trucks from since 1970 or so) has a 41 tooth ring gear and a 10 tooth pinion to make a 4.10 ratio (41/10). The Dana 44 front axle could have had a 45 tooth ring and an 11 tooth pinion, giving a 4.090909 ratio (4.09).

The Ford trucks with the 9" rear and Dana 44 front would have 37 tooth ring and 9 tooth pinion in the 9" rear, giving a 4.1111 (4.11) ratio, while having the same 4.09 Dana 44 in the front.

The difference in ratio in factory trucks has nothing to do with the transfer case, it's only the manufacturer and design of the axle.

Unquote

Cheers,

FourWheelDrift

Last edited by FourWheelDrift : 28th February 2009 at 13:25.
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Old 28th February 2009, 14:04   #40
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Quote:
Originally Posted by FourWheelDrift View Post
All 4x4 light trucks (1 ton and under) have the 'same' ratio in the front and back from the factory. The reason for different ratios, like 4.09 and 4.10 is the difference in axles and tooth combinations for those axles. Every GM that has a Dana 44 front axle and GM rear axle has different ratios due only to design differences in the differentials (factory differentials that is).
So does it mean that these differentials have a different gearing inside? And this will not cause axle windup?
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Old 28th February 2009, 15:02   #41
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Originally Posted by DKG View Post
Sometimes just torque doesn't help. You need momentum too, which is where the 4H gears come in.



Well said Shahnawaz. Its actually a part of getting to know your vehicle intimately. How it behaves in different terrain. How the tyres respond. Where do you need torque and where do you need more momentum. Watching closely and choosing the right tool to get you out, that to me is offroading skill.

As one doesn't know the full context of Mr. Dhabar's advice on extensive use of 4L it may not be fair to quote him. In all probability his advice applied to a particular type of terrain encountered on the GE's.

Its more fun to graduate through your gear options to the 4L ratios as a last resort. Let the terrain dictate what gear you use and whether its torque alone or momentum or a combination of both which is needed to get you out.
Dear DKG & Shahnawaz,

Very well said indeed. Now we are talking skill based offroading rather than raw power based one.

DKG - The last paragraph is the essence of offroading.

"Offroading gives a better high than Single Malt" !!!

Regds

Amit
(NIOC)
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Old 28th February 2009, 18:30   #42
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Originally Posted by DKG View Post
Sometimes just torque doesn't help. You need momentum too, which is where the 4H gears come in.
DKG, just thinking about this. The 4th gear in low is pretty fast, that's already trail driving fast, same as 2nd high. The next usable gear would be 3rd in 4H. I thought that is good for only sand driving or trail driving. Anyway, tomorrow at the Bangalore OTR I'll keep a close watch on people who do it in 4H. No, not Shahnawaz's Gypsy, that Mutant Ninja Gypsy can't be used for any benchmarks.
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Watching closely and choosing the right tool to get you out, that to me is offroading skill.
Until I get that, I'll stick to my thumb rules..
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As one doesn't know the full context of Mr. Dhabar's advice on extensive use of 4L it may not be fair to quote him. In all probability his advice applied to a particular type of terrain encountered on the GE's.
I know the context since I have discussed this wirh Behram over phone too. Eariler MGEs were real 4x4 challenges and were held in all kind of mad terrains, deserts to tropical forests.
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Old 28th February 2009, 18:32   #43
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Mr Dhabar is absolutely correct! He is most technically qualified amongst us. All that we can contibute is with our experience.
The comparision in the ratios of between a Gypsy and Mahindra are different. A Mahindra when used on tarmac for extended distance(500 kms plus) result in a different wear of tyre in the front and the rear and again Gypsy had shown different pattern(courtesy army drivers driving down from higher reaches of Poonch and failing to shift to 2H)
Mr Dhabar may like to correct me if I am wrong but the front suspension also feels less responsive when on tarmac in 4H mode. However, over the period of time with the newer models the suspension is broader(width of leaf spring) inspire better handling both off and on road.
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Old 28th February 2009, 18:50   #44
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Shahnawaz's Gypsy, that Mutant Ninja Gypsy can't be used for any benchmarks.
I liked that name Mutant Ninja Gypsy
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Old 28th February 2009, 19:09   #45
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Until I get that, I'll stick to my thumb rules.
Dear Samurai,

Try engaging 4L just before the obstrucle otherwise try driving on 4H all through the OTR even 2x4 for normal dirt track.

I personally do not mind changing gears as per the track demands. Further if at all the jeep stalls in 2x4 somewhere engage 4x4 H 2nd or even 4L and move out. Big Deal. Why be wary of changing gears.

No harm in asking Shahnawaz or other senior jeepers for the right Gear for the obstrucle. This is the way our NIOC seniors teach, and we teach our jouniors.

When I started our RBS MOD (Rabinder Singh) sat in my Jeep with me and he did not let me engage 4x4 on most of the track. Even when i got stuck he got guys to pull me out so that I dont have fear of getting stuck. Further this gave me control on my torque and momentum.

I would even recommend trying some easy climbs on 4H 2nd with some momentum. Outer most what will happen, your Jeep will stall in the middle of the climb. Just Break engage 4x4 L reverse and back up. then try 4x4 L 2nd. This is the way you would learn the potential of your vechile.

With this you will compound the thrill of crossing the obstrucle. Lucky u have an OTR tomorrow to try this out. HAPPY OFFROADING

This is just a freindly suggestion after all we are trying to exchange and learn skills of offroading by discussing different experiences.

Correct me if i am worng Shahnawaz/DKG in this suggestion.

Regds

Amit
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