what axle/diffs 130 defender

[squidsd1]

I'm looking at a 2004 130defender td5 and I currently have a 1997 300tdi disco manual with rear Detroit locker if I purchased the defender could I change diff housings (im aware of disco having donut and defender having uni) but are they same 24 spline shafts and is still the same housing?

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[Bush65]

The short answer is that it is not a straight forward swap of those parts.

The 130 rear axle assembly will have a 'P38' style diff, the 300Tdi has a 'rover' diff.

Edit: unless a previous owner of the 130 has swapped the rear axle assembly for a 'Salisbury' which has a stronger diff again.

[uninformed]

John, do you know from LR, or your own opinion, if the P38 type axle housing is stronger than the Rover type axle housing?

[MLD]

Ashcroft (UK) are selling a P38HD conversion which is in essence a new 3rd member housing with a Rover diff centre/C&P. Not sure if Ashcroft will sell the housing alone but that could be an easy swap for you to keep the rover detroit centre. You will have to shorten the prop shaft to suit the longer 3rd member.

The reality of cost you might as well buy a new detroit centre and axles for the P38. Don't forget to add the cost of a replacement diff centre and axles in the Disco if you do the swap.

For $1400 you can buy a complete SH salisbury from a wrecker, add a 4 hours for labour to bolt it up and bobs your uncle.

I've deliberately left alone the debate about the P38 diff strength.

MLD

[squidsd1]

thanks heaps guys would utopian be the same for 300tdi defender aswell? sorry for noob question

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[isuzurover]

thanks heaps guys would utopian be the same for 300tdi defender aswell? sorry for noob question

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I have NFI what you are saying, but assume you are asking if the rear diffs are the same. Short answer is No. 300tdi disco has a rover diff front and rear, 300tdi defender has a rover front and Salisbury rear.



Ashcroft (UK) are selling a P38HD conversion which is in essence a new 3rd member housing with a Rover diff centre/C&P. Not sure if Ashcroft will sell the housing alone but that could be an easy swap for you to keep the rover detroit centre. ...

Umm, no. The Ashcroft conversion is a hypoid setup. The exra strength is in the Hypoid CW & P. If you buy the diff casing alone you will have a pile of useless parts.

[weeds]

I guess the first question would be are they all the same ratio

I believe all three would bolt in in however prop shaft would need to be sorted

[Bush65]

John, do you know from LR, or your own opinion, if the P38 type axle housing is stronger than the Rover type axle housing?
Sorry I don't know. I haven't had a chance to examine the P38 type housing close enough. It should be easy to check wall thickness at the breather hole, but I would need to see one stripped out to be able to form an opinion. It would be helpful if the bare housing weights could be compared. I would be surprised if Land Rover haven't increased the housing strength from a P38 RR to Defender 130, but ........


Ashcroft (UK) are selling a P38HD conversion which is in essence a new 3rd member housing with a Rover diff centre/C&P. Not sure if Ashcroft will sell the housing alone but that could be an easy swap for you to keep the rover detroit centre. You will have to shorten the prop shaft to suit the longer 3rd member.

The reality of cost you might as well buy a new detroit centre and axles for the P38. Don't forget to add the cost of a replacement diff centre and axles in the Disco if you do the swap.

For $1400 you can buy a complete SH salisbury from a wrecker, add a 4 hours for labour to bolt it up and bobs your uncle.

I've deliberately left alone the debate about the P38 diff strength.

MLD
Firstly, the Ashcroft P38HD upgrade for Defenders does not use the rover ring and pinion, it requires a unique Ashcroft R&P. However AFAIK you are correct in that it uses a Rover (not P38) diff centre/hemisphere. I believe a Rover centre with Detroit from a Disco could be used.

Secondly your advice about using a complete SH Salisbury should have a caution applied about the difference between a Salisbury for a 130 and the more common Salisbury from a 110. The 130 Salisbury has thicker axle tubes to suit the higher GVM.

[uninformed]

I guess the first question would be are they all the same ratio

I believe all three would bolt in in however prop shaft would need to be sorted

just to be clear (since there is some miss information already in this thread), you do mean complete axle assemblies don't you (not diff centres/3rd members etc)

And yes a Sals from a defender, Rover coil sprung and P38 from a defender are all 3.54-1

[MLD]

Secondly your advice about using a complete SH Salisbury should have a caution applied about the difference between a Salisbury for a 130 and the more common Salisbury from a 110. The 130 Salisbury has thicker axle tubes to suit the higher GVM.

Since we on that topic. Can anyone clarify if the axle housing for the P38 under a 130 is stronger, weaker, comparable in strength to a salisbury from a 110. If the 110 salisbury and P38 130 axle housings are comparable strength it might be all a bit academic that the 130 salisbury is stronger again. I'd like to know the answer because i'm in the process of building a 130 and i have a 110 salisbury with maxi locker under a 110 ready to be swapped over if the numbers for the Ashcroft P38HD conversion don't stack up.

Cheers MLD

[Bush65]

Since we on that topic. Can anyone clarify if the axle housing for the P38 under a 130 is stronger, weaker, comparable in strength to a salisbury from a 110. If the 110 salisbury and P38 130 axle housings are comparable strength it might be all a bit academic that the 130 salisbury is stronger again. I'd like to know the answer because i'm in the process of building a 130 and i have a 110 salisbury with maxi locker under a 110 ready to be swapped over if the numbers for the Ashcroft P38HD conversion don't stack up.

Cheers MLD
IMHO it would be cavalier of anyone to make such comparisons. The construction of a Salisbury housing is not remotely similar to a welded Rover or P38 housing.

Regarding strength of axle housings,there are 'Static Strength' and 'Fatigue Strength'.

I have little doubt the static strength is an issue. All will have a reasonable 'Factor of Safety' designed in, and replacing the axle housing with one having a lower static strength, will simply reduce the 'factor of safety'.

It should take a gross overload such as a collision to exceed the static strength. In circumstances of such high overload, there will most likely be other damage or even injuries to completely ruin your day.

Fatigue strength is a very difficult matter to grapple with. 'Stress Raisers' don't affect static strength but they have a huge impact on fatigue strength.

Fatigue failure usually takes the form of a crack that starts at a small defect in a region of fluctuating stress (considerably lower than the static stress), at a stress raiser. The crack propagates during the fluctuating stress cycles, until the amount of material resisting the load is reduced so much that it fractures. Most have heard stories that go like, "it broke in my driveway ...".

The critical regions and stress raisers and the cause of the stress raisers are what are so different between a Salisbury and Rover/P38 axle housing, that it is like comparing the old "apples and oranges".

With the Salisbury, the issue is the transition from a massively rigid cast housing for the diff, to the significantly less stiff axle tubes. This creates a stress raiser in the axle tube at the point where it exits the diff housing.

Increasing the thickness of the axle tube does two things; it increases the stiffness of the tube, thus reducing the stress raiser to some extent, and it also reduces the magnitude of the stress by virtue of spreading the load across a greater cross sectional area.

With the Rover/P38 housing, the transition in stiffness from the 'Banjo' diff housing, to the axle tubes is gradual, resulting in no perceptible stress raiser. The load carrying material in this region is continuous (no join). However the parts of the pressed housing are welded together and it is these where fatigue cracks are likely to form.

The static strength of welds is often greater than the parent metal, due to use of higher strength filler material in the welds. However the fatigue strength of welds is much lower than that of the parent metal, and varies greatly depending upon the location of the weld compared to the direction of the principle stress. Transverse welds being the worst case.

Identical (even to 'forensic' examination) items have widely varying fatigue strength, and so it is predicted with 'statistical chance'. This statistical nature means that one item can have a much lower Fatigue Strength than predicted, another can be be much higher, but we 'hope' 90% will exceed the predicted strength.

The affect of 'Fatigue Damage' incurred during a particular 'Load Cycle' depends very much on the 'Magnitude' and 'Direction' of the 'Stress' during each 'load cycle'. The 'fatigue damage' is 'Cumulative'. So one high magnitude cycle is equivalent to numerous lower magnitude cycles.

The fluctuation in the stress is of the utmost importance, not only the magnitude but whether the stress direction is in the same direction or if it reverses direction during some cycles. Reversing is much worse.

What this all means is that many can drive around for the entire life of the vehicle and not experience a problem. However a vehicle heavily loaded and driven over many kms of corrugations will have a reduced 'Fatigue Life'. A few heavy load cycles, e.g. hitting an unexpected wash-away at to high a speed will take away a significant portion of your fatigue life.

What I am certain of is that Land Rover state a higher rear axle load capacity for the 130 than for all but the 'Heavy Duty' option for some 110 Defenders. Furthermore we know that they increased the strength of the Salisbury axle for the 130 and the 'HD' 110.

If you hardly use the 130 loaded up, for many kms of rough roads, and you are lucky enough to get a 110 Salisbury that has had an easy life and is one of statistically fortunate ones, then you may have a happy future after installing it.

Edit: there is nothing to stop you from replacing the axle tubes in a Salisbury with tubes having a thicker wall. Another alternative which has been used is to weld another tube inside the existing axle tube (so called laminating). I appreciate both options are a pain with the Maxi-Drive locker.

[uninformed]

As usual John, thank you for taking the time for such an imformative reply.

:)