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Old 29th July 2008, 09:04   #16
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Quote:
Originally Posted by Samurai View Post
Shahnawaz, when you are posting info and images from other sources, please mention the original source/link at the bottom.
ooppsss.. my mistake. will PM you the links and maybe you can help to insert the source links below the images.

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Originally Posted by Alfa_Kilo View Post
@KS

R&P means Ring and Pinion when we are talking axles, Rack and Pinion is for a steering.
.
I Agree. I meant Ring and not Rack.

Last edited by Rehaan : 29th July 2008 at 22:08. Reason: Please use the MULTIQUOTE or EDIT button.
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Old 29th July 2008, 14:54   #17
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Default Crawl Ratio

"Crawl Ratio" is the term used to indicate the 'number' derived after multiplying the first gear ratio(of the transmission), T-Case Ratio (L Range), axle ratio.

It denotes the ability of a 4x4 to "crawl/creep" along (without depressing the accelerator) at very low speeds. This is very essential in rocky terrains.

The higher the crawl ratio, the better the off-road capabilities.

Let's calculate the 'crawl ratio' using our example of the Gypsy/Classic:

Gypsy: 3.652 * 2.268 * 3.727 = 30.869
Classic: 3.986 * 2.460 * 4.880 = 47.851
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Old 29th July 2008, 16:34   #18
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Default Improving the crawl ratio performance of 4x4

Disclaimer: This is purely about improving "crawling ratio" from the 'gearing' point of view. There are MANY other factors that go into improving the performance of a 4x4

So let's take the example of the Gypsy which has a crawling ratio of "30.869". Assume that we want to improve it's crawl ratio, so that it becomes more capable of climbing rocks on very very low speeds.

Considering that the crawl ratio is impacted by the 'transmission ratios, t-case ratios & axle ratios', we have 3 choices to increase the crawl ratio.

The most easy and often used option is to "alter the gearing ratio of the T-case". This is "the most bang for the buck" mod for increasing the rock crawler capabilities of a 4x4.

The stock T-case ratio of the Gypsy is 2.268 (L-Range). here are the crawl ratio's for the Gypsy if we put in 4.16, 5.14 or 6.5 gear kits in the T-Case.

Gypsy Crawl Ratio:
-----------------
Stock T-case: 30.869
4.16: 56.62
5.14: 69.96
6.50: 88.47


NOTE:
  • The size of the tyres also play a significant role in the crawl ratio and that also needs to be kept in mind.
  • Lowering the the T-case gear ratio will put a lot of stress on the vehicle. T-Case mounts, sometimes even the output shafts etc need to be strengthened.
  • Increasing the crawl ratio will have a -ve impact on your street/highway drive-ability of your 4x4
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Old 5th November 2008, 17:02   #19
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I have a question for the folks here, Behram sir if you would know.

For FJ470 DS4 (the S4 engined) had an axle ratio of 4.27
For FJ470 DP (The XDP 4.90 engined) had an axle ratio of 5.88

My questions are:
1. Firstly is the above correct? I have collected information over the years and this is what i have. Please do let me know.

2. Considering 1 is true. Can the axle on the DP engined be used on any of our jeeps? Considering all parameters.

Also another thing i have noticed with the Mahindra axles. How many axle ratio do we have/had?

I know of:
1. 5.88:1 FJ740/470 DP
2. 5.38:1 CJ340
3. 4.88:1 CL340 Classic MM540/550
4. 4.27:1 FJ740/470 S4
5. 3.73:1 Mahindra Legend, CL 500

Are these all?

If you try and sort out the combinations of engines, gearboxes and the axle ratio of the various models that Mahindra sells and is selling you will do this not once but many times i will keep it at 1 or the mods might come visiting me again.

I did a fair bit of digging around and i am still confused.

Behram sir, does Mahindra keep track or am i the only one doing it?

And finally can i get the 5.88:1 on my 99 model Classic?
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Old 5th November 2008, 17:18   #20
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Dear Spitfire - your queries - FJ Simpsons = 4.27 is correct. FJ XDP4.90 = 5.88 is correct. XDP4.90 engine was regularly used in the CL340 / MM540. Axle ratios used are 3.73 / 4.10 / 4.27 / 4.30 / 4.55 / 4.88 / 4.90 / 5.38 / 5.88 / 6.80. For putting 5.88 on your CL340 you will obviously have to change front axle crown pinion also. Obtaining a 5.88 pair will not be simple. FJ was 4 pinion axle, CL was 2 pinion axle, FJ was semi floating converted to fully floating, CL was only semi floating. Track of FJ is more. KPI of FJ is different from CL. FJ is underslung, CL is overslung. FJ pinion line angle to datum is different from CL.

Same request again - don't do anything just like that, it will backfire very badly.

Best regards,

Behram Dhabhar
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Old 5th November 2008, 17:34   #21
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Quote:
Originally Posted by DHABHAR.BEHRAM View Post
Dear Spitfire - your queries - FJ Simpsons = 4.27 is correct. FJ XDP4.90 = 5.88 is correct. XDP4.90 engine was regularly used in the CL340 / MM540. Axle ratios used are 3.73 / 4.10 / 4.27 / 4.30 / 4.55 / 4.88 / 4.90 / 5.38 / 5.88 / 6.80. For putting 5.88 on your CL340 you will obviously have to change front axle crown pinion also. Obtaining a 5.88 pair will not be simple. FJ was 4 pinion axle, CL was 2 pinion axle, FJ was semi floating converted to fully floating, CL was only semi floating. Track of FJ is more. KPI of FJ is different from CL. FJ is underslung, CL is overslung. FJ pinion line angle to datum is different from CL.

Same request again - don't do anything just like that, it will backfire very badly.

Best regards,

Behram Dhabhar
Thank you Sir.

I knew there are a lot of factors involved and some i didnt. Thanks for clarifying.

I am very careful before doing anything on the Classic. I believe stock is best. But sometimes the urge to try and improve makes you think out of the box. Not that it is correct always.

I thought of increasing the track of the CLS by adopting spacers + negative offset rims. Abandoned it after i calculated the forces that may be acting on the axle due to such a modification. Under some offroad conditions the lugs or the axle itself may snap.

Presently my CLS is stock except that i use the CJ340 rims whenever i go offroading the spokes get dirty easily and sometimes entangle a lot of vegetation in them.

Thank you again. I will keep asking a lot more queries though.
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