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Old 19th September 2008, 11:05   #1
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Default Axles: Live/Dead, Semi/Full Floating etc..

In 4x4 settings, one often hears the term 'oh you have got full float axles', or 'this has live axles', or 'oh you have wide axles..' etc..

Can we attempt to "de-mystify" the types of axles that a 4x4 can have in 'simple, non technical, non jargon, easy to understand' terms?

On the internet one can find the 'technical definition' of all these and what they mean but it would be great if the experienced folks here could share on
  • What are these different kind of axles -- for both front & rear
  • What are the pros/cons of each type
  • In which situation which would be better
  • Examples of which 'common Indian)' 4x4's has which kind of axles
  • Experience of 'personally having these in your own 4x4'
Also, later we can discuss on what precautions one should take while changing from one axle type to another for their 4x4's.

Cheers,
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Old 19th September 2008, 11:28   #2
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Nice thread infact few days ago I wanted to demystify myself the art of finding out whether a axle is full floating or semi floating by looking at it.

I will pen down what I know

Fully floating axles are used in higher load carrying applications compared to the Semi floating axles.

You can find fully floating rear axle in Mahindra commander. I dont know the exact answer for the which situation which would be better but I believe the axles are decided upon the kind of application one puts into use like the amount of load he carries. In the fully floating axles the shaft bears no load it simply transmit the power. Its not the same in the case of semi floating.

Mine is a rookie answer !! I believe experts should refine it up
hope any similar kind of thread doesn't exist
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Old 19th September 2008, 14:33   #3
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My two bits on axles:
  • What are these different kind of axles -- for both front & rear
  • What are the pros/cons of each type
  • In which situation which would be better
  • Examples of which 'common Indian)' 4x4's has which kind of axles
  • Experience of 'personally having these in your own 4x4'
Live axle - These are the axles that drive the wheels. The rear axles on a rear-wheel drive and the front-axles on a front wheel drive are live axles. Dead axles are used on the non-driven wheels. Eg. Front axles in a 2wd Scorp. In multi-axle trucks the driven wheels contain the live axle, while the others are dead axles only distributing the load.

Full-floating axle: These are non-load bearing axles. Here, the axle will be a single shaft going to the differential on one end and to the hub (where it is attached through splines). Its sole job is to propel the vehicle, not bear weight. The weight is borne by the axle housing assembly, hub, wheel and suspension. It's better for larger load carrying as it won't strain the axle. Among M&M vehicles the Mahindra Marshall / Commander has this kind of axle. Many trucks also use this.

Semi-floating axle: Here the axle also bears a bit of the load. A semi-floating axle will have splines that attach to the differential on one end and directly attached to the hub on the other end. It is also supported by a bearing between the housing and axle, but it bears the weight of the hub. The Scorpio has a semi-floating design front & rear. So does the Gypsy.

Haven't heard of wide axle - do you mean "wide track"? The MG413 Gypsys are "wide track" and so were some MG410s post 1992 or something. (The earlier MG410's had a narrower track width - the distance between the two wheels on the same axle.)

Hope this helps.
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Old 19th September 2008, 16:58   #4
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well,
iam trying to be as common manly as possible.
Hope this makes it clear.

Dead axle
There is a pipe with nothing inside but just the wheels attached to both ends. This is called dead axle. The front axle in a 2 wheel drive jeep.

Live axle

If there is a pipe with another rod rotating inside then it is called live axle.
They are of a few types, but lets discuss the floating and semi floating types. Just like a ballpoint pen with a refill inside (as posted by someone in the forum)
The pen is called the axle hosing (pipe) , the refill is called the shaft(rod) which comes from the differential and drives the wheel.

Semi floating type.
When a rod is rotating inside a pipe, it shouldn't touch the pipe inner right. so, a bearing is placed inside the pipe. ie, the bearings outer dia touches the pipes inner dia and the rod comes thru the bearings inner hole. So the bearing helps in easy movement of the rod without touching the pipe. The wheel is attached to the end of the rod.
Here the weight of the whole vehicle is on the rod and the bearing holding the rod(as the wheel is attached to this). if the shaft breaks, the wheel comes out and the vehicle cannot be used.
Used in the rear wheels of mm540 jeeps(not sure though).

Full floating
In a full floating, the wheel is not attached to the rod directly. it is attached to the pipe. The rod inside connects to the hubs of the wheel to turn it. So the rod doesn't bear any weight and floats inside the pipe.
The weight is not on the rod but on the pipe. Also when the rod breaks, just remove the rod from the pipe and the wheel can just keep spinning. We can atleast tow the vehicle.
The front wheels of 4x4 mm540 jeeps.
Name:  axle.JPG
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krishna.
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Old 20th September 2008, 07:17   #5
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hi your explanation was great, but instead of conveying things as rod and pipe you could have gone saying shaft and shaft housing or some other thing. This ain't very technnical jargon !!
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Old 28th October 2009, 12:47   #6
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Here is an image I shot at VITM, Bangalore. It is a technology museum. See in full size.

Axles: Live/Dead, Semi/Full Floating etc..-imag0011.jpg
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Old 16th December 2009, 00:09   #7
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The explanations are great. Thanks guys. Maybe now we should get into more details for the benefit of noobs like us.
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Old 15th January 2010, 17:46   #8
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Quote:
Originally Posted by khan_sultan View Post
..... later we can discuss on what precautions one should take while changing from one axle type to another for their 4x4's.
Giving life to this thread...

If I were to change my CJ340 rear axles from Stock to FFRA, what are the parts I Need To/NEED NOT change?

1) Axle housing - I am sure nothing changes here.
2) Brake drums,wheels,tyres - I am sure nothing changes here too.
3) Axle - The iron rod that connects the diff to the wheel - SHOULD change. My question is, what is the part (Part#) that would fit a CJ340 rear axle? Is it easily avbl off the shelf (5x0's ?) ,or should I search around? Please advice.
4) What other 'specific' part should one add/replace/buy for this conversion? Any increase in # of bearings from current 1+1 setup?

Thanks in advance...
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Old 15th January 2010, 17:53   #9
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Santosh, if you look at the image I have posted, axle housing is the biggest change. Also, you won't get FFRA setup in 48 inch size.
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Old 15th January 2010, 18:02   #10
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If we imagine ourselves to be the fully floating axle it must feel a lot like a weary traveller who feels sudden relief as he acquires a trolley for his bags than having to lift the luggage and walk
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Old 15th January 2010, 18:44   #11
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Question

Quote:
Originally Posted by Samurai View Post
Santosh, if you look at the image I have posted, axle housing is the biggest change. Also, you won't get FFRA setup in 48 inch size.
Sharat, Nope - I "think" it is possible, just that I wasnt too technically inclined back then (below) to learn about it... I have invited Baburajs to comment in this thread on his experience. AFA I remember, it had the stock axle housing, I could be grossly wrong too.

Axles: Live/Dead, Semi/Full Floating etc..-baburajs.jpg

Last edited by svsantosh : 15th January 2010 at 18:50.
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Old 16th January 2010, 03:20   #12
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Hello Santosh,
it may be interesting to note that the semi floating (Dana 44) vs full floating rear drive axle system(as found in the earliest Jeeps of the WWII era), can be incorporated into our jeeps with std. 4 ft.track.
To make things clear, it (FFRA) has a twin bearing hub setup, which allows the total vehicle weight to be borne by the differential housing tube, as common in commercial vehicles like trucks. The axle shafts are fully floating as the name suggests.

The reqd. modifications to switch over is what we need to learn correctly.

1. The legendary Dana 44 rear differential housing can be joined/attached with a spindle, (from the front diff), and a front hub carried by two bearings.(501349 or the later ones cannot remember the size right now).
2. The live axles in question being adaptable to 48in. track, could be sourced from a WWII jeep.
3. The most important thing that many such 'converters' ignore is the oil seal, at the crown side, which arrests the gear oil to be spun and brought to the hub by the axles.

I can say that a Dana 44 converted to full floating in the correct way is a bullet proof differential to use under adverse OTR conditions.
Please note that the old model axles came with 10 splines.
Jeepers with 19 should get a pair of 10 teeth bevels, before conversion. Any doubts are welcomed to be cleared.
All the best. with you always..................... UBS
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Old 19th January 2010, 18:11   #13
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Hello Sharat, UBS Sir,

I spoke to BabuRaj and learnt he is busy to post his experience for now. What I heard from him (Sharat, you are correct), the whole Axle housing is to be changed. He got 1 from Gujuri and exchanged it with his stock one. He paid 2K over and above the exchange. He couldnt recollect all other spares, but whole bill came upto ~3500 (includes the housing, labour).

I am thinking since 48" track FFRA never came in CJ340 time period, Babu must have got a Willy's or a similar old one for sure. I will do some more research and add details in future.

Babu, meanwhile post you MOD experience if time permits (Hope your wish doesnt come true - to see the real fruit of a FFRA after a axle break)
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Old 21st January 2010, 22:51   #14
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Yes the FFRA sourced was from a old generation jeep and it is indeed a 4 Ft one. The conversion itself went without much hassles but as UBS sir pointed out we forgot the oil seal. That is corrected now and is working great. Have had some very tough off roading situations and it havent caused any problems.

As Santosh has already mentioned the bill came to around 3 to 3.5 K including spares and the labour.
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Old 12th March 2010, 13:01   #15
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I found this pic very useful, in understanding the loads on the different types of axles.

However, I fail to understand the load distribution on the axle shaft bearings used in semifloating axles.
a) Ball-type bearing
b) Straight-roller bearing
c) Tapered-roller bearing

Can someone help me out with a rendering.

Edit: Another query on the safety of semi-floaters.
Wouldnt the retainer piece be sufficient to hold the axle in place, if the shafts break? How often does the shaft break exactly at the flange?
Attached Images
 

Last edited by Rocky_Balboa : 12th March 2010 at 13:10.
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