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Old 16th October 2008, 17:18   #1
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Default Using MM540 axles in CJ340

While the CJ340 enjoys definite advantage over MM540/550 in off-roading, but there are times when I am envious of MM540/550 owners. The MM5xx definitely has better ride comfort and better handling on road.

Since traveling to off-road venues involves lot of on-road driving, I want to improve the handling aspect of CJ340. The curving roads in my area that can be easily managed at 80Kmph on GV, is scary on CJ340 even at 50Kmph. And this on a soft top. Jammy, the previous owner of the Jeep tried compensating by switching to wider tyres. While that helps, I like to have some more.

I have noticed that many SWB Jeepers have switched to MM550 axles to get a little wider track there by gaining better handling characteristics.

I want understand the pros and cons of using MM5xx axle and axle housing on a CJ340/CL340. I understand the pros, but what is the downside?
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Old 16th October 2008, 17:23   #2
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Easiest way to widen the track is to use very negative offset alloy rims.
And for a 4x4,these are commonly available.
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Old 16th October 2008, 17:30   #3
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Originally Posted by nitrous View Post
Easiest way to widen the track is to use very negative offset alloy rims.
That was my first thought, but one has to consider the cantilever stress on the bolts.
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Old 16th October 2008, 17:36   #4
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Quote:
Originally Posted by Samurai View Post
That was my first thought, but one has to consider the cantilever stress on the bolts.
I tried the same or was trying the same on my Classic too.

But i was going the -ve offset + spacer + stock size tyres route. Did some maths(and physics) on the stress to be borne by the axle due to the widening of the track. And it seemed on paper that i need to strengthen the suspension too. The project never took off though. Will try and dig up those figures. Had created an excel sheet to calculate the optimal track size for a particular GAWR(considering its equal on each side) on the stock axles. Cant find that excel too :( will have to put it together again.

You do get better quality lugs. Or can get them made.

Also if you are increasing the track only for handling on sharp turns, not recommended. If not done properly can but a lot of stress on the suspension and even the Chassis of the Jeep. I have seen bolting points on the chasis broken off due to a bad job when taking such a modified jeep offroad.

Last edited by Spitfire : 16th October 2008 at 17:45.
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Old 16th October 2008, 17:47   #5
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Quote:
Originally Posted by Samurai View Post
I want understand the pros and cons of using MM5xx axle and axle housing on a CJ340/CL340. I understand the pros, but what is the downside?
It is going to effect the steering, obviously. Do these guys swapping axles also use a mm5xx steering box etc.? Can you install power steering in a way that will give you "feedback"? There was a post by Behram awhile back that looks ominous. I thought it was all "bolt in".

So, it will effect your steering. My further question correlative to Samurai's is can you solve hard or "vague" steering in a jeep by adding power steering?

Quote:
Originally Posted by DHABHAR.BEHRAM View Post
.... Also I will need to drive your vehicle with power steering to ascertain whether it is OK or not because in this case we cannot change camber and for changing caster we may need wedges between the springs and the axle. These are normally made in tool room as a 1 degree angle is very difficult to machine in an uncontrolled situation. Then for production, the axle spring seat weld angle is changed. These actions are required for power steering as torque needs are different otherwise you will get a feeling of flotation and the garages will go on doing all sorts of things till the cows come home but the problem will not get solved. It will leave you bewildered.
It leaves me bewildered.

Last edited by DirtyDan : 16th October 2008 at 17:50.
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Old 16th October 2008, 17:51   #6
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Spacers create complications on-road.
So, barring spacers, how much difference in the offset(in mm) would the aftermarket rim and stock figure be?
This could help in figuring out the difference in stress levels.

Let me add something important here.
Even with the track modification, please keep in mind that the ultra-short wheelbase and the high CG of the CJ3B is inherently a dicey vehicle when it comes to handling and you've got to keep the speeds in control.

Once, I've had a sudden braking situation in a CJ3B shod with Pirelli 215mm wide AT tyres. Scary would be an understatement.

Last edited by nitrous : 16th October 2008 at 17:53.
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Old 16th October 2008, 17:56   #7
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Quote:
Originally Posted by DirtyDan View Post
It is going to effect the steering, obviously. Do these guys swapping axles also use a mm5xx steering box etc.? Can you install power steering in a way that will give you "feedback"?
I am told that steering becomes easier. Anyway, I am not even considering power steering since the current steering setup doesn't bother me. Besides, a power steering that is not speed sensitive can be a bigger problem.

Quote:
Originally Posted by nitrous View Post
Once, I've had a sudden braking situation in a CJ3B shod with Pirelli 215mm wide AT tyres. Scary would be an understatement.
I have 235mm wide AT tyres.

Last edited by Samurai : 16th October 2008 at 18:11.
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Old 16th October 2008, 18:25   #8
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Samurai, as you know my rear axle packed up due to all the mods of diesel -> petrol -> diesel conversion. Behram & Ferdi STRICTLY recommended sticking to a stock Classic axle. Which is still produced by Mahindra BTW.

That's enough for me.

Quote:

Once, I've had a sudden braking situation in a CJ3B shod with Pirelli 215mm wide AT tyres. Scary would be an understatement.
You should try braking in the Classic. Rehaan was riding shotgun with me when we braked all of a sudden from moderate speed. No tantrums, no swerving...very safe. Of course, the brakes have been recently overhauled & the master cylinder is new too.
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Old 16th October 2008, 18:27   #9
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Quote:
Originally Posted by Samurai View Post
I am told that steering becomes easier. Anyway, I am not even considering power steering since the current steering setup doesn't bother me. Besides, a power steering that is not speed sensitive can be a bigger problem.

I have 235mm wide AT tyres.
Samurai Sir,
Just my guess, with reference to Headers post regarding tyre size.
If you reduce/ change the tyre size (w.r.t. Radius) will it help?
Since main problem could be because of length of the Jeep. (its wheelbase is 80" na?)
So before chassis or suspension alteration I think giving a try to different tyre size might help a little.
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Old 16th October 2008, 18:54   #10
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Quote:
So before chassis or suspension alteration I think giving a try to different tyre size might help a little.
He's running on 235 size AT tyres which is more than enough for off-roading and tarmac too.
Going anymore wider will just make it look like those show-off GPWs in the north.
Moreover, have you checked the prices of tyres to think about experimenting?
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Old 16th October 2008, 21:44   #11
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Quote:
Originally Posted by nitrous View Post
Moreover, have you checked the prices of tyres to think about experimenting?
Sorry for that, may be I was too much into tyre things. (I didnt mean to try those show off balloon tyres)
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Old 17th October 2008, 04:28   #12
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There will be LESS stress on spindles and lugs if spindles and lugs are also from the mm5** (why wouldn't they be?) since the SWB jeep weighs considerably less than the mm5**. There will be differences in spring loads between the 2 jeeps. I would wonder if the SWB springs can hold the heavier mm5** axles adequately. Or, if you also install mm5** springs (too big?), I wonder if you then would have to make adjustments for the lighter SWB jeep weight...else, harsh ride. Do the axle housing/chassis attachment points line up vertically? The steering linkage to the front wheels is another issue. New mm5** steering box etc?

The above is just sheer speculation on my part. I have no experience with this whatsoever. Seems complex.

Last edited by DirtyDan : 17th October 2008 at 04:39.
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Old 17th October 2008, 07:28   #13
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Well, that's enough to scare me away. I guess I'll stay stock. I am not capable of managing such complex mods. And I never do mods that I don't understand or consider unreliable.
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Old 17th October 2008, 10:38   #14
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Hello Sir,
not to be confused by all the above posts.
All the jeeps (not SUVs) made by Mahindra have almost the same knuckle, spring, spindle,etc.
Once you put the 3 inches wider MM540 axles, your 340 get the specs of the Mahindra Classic. Rest is all well known to Classic owners, about stress, stability, strength etc.
Go ahead and simply swap the differentials for wider track. If possible try and source them off a MM550, you will get disc brakes in front and limited slip rear crown/tail assy.

For fat tyres get a steering box of 'Ranee', the ones used in 550s and Armadas, it sits straight into the old position.
If you have to opt for disc brakes in front, then it is better you instal a servo assisted brake unit, which again will call for a suspended pedals setup and a modified alternator with inhouse pump.
Very few minor things to keep in mind during such an upgrade, and right now I am in a hurry, so will not able to point them, we will seek the advise of experts on this issue. The emergency brake, the shock absorber lower point and a few are there
We have many upgraded CJ3B, Kaisers and some WWII jeeps with 540 and even FC differentials (with matching axle ratio as per the power train and wheel dia.) in our club Jeep Thrills, where offroading is at the A+ level, still there is no fear in the most difficult terrains, just that we always prefer going full floating at the rear too due the massive beating to our jeeps. "The key to success is the 'feather' weight SWB jeeps."

BTW, if you use MM550 rear, I am told ( not very sure) that it is difficult to convert to full floating, as the 550 axle shaft's outer dia is higher than the standard Dana 44 axles, causing mismatch with the spindles' inner bore. Please check on this issue and report to the forum.
Good topic taken up, let the knowledge flow in.
With all my wishes,
yours.....................................UBS
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Old 17th October 2008, 10:50   #15
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Quote:
Originally Posted by GTO View Post
You should try braking in the Classic. Rehaan was riding shotgun with me when we braked all of a sudden from moderate speed. No tantrums, no swerving...very safe. Of course, the brakes have been recently overhauled & the master cylinder is new too.
Of course, the fact that you had disc brakes made a massive difference too. Till I fixed discs on my old jeep, I used to have a scare every time I used it after a couple of days break! The damn thing would suddenly swerve on applying brakes.
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