Axle dilema

[UKTJ]

I hope to be able to get my TJ regeared and ARB air lockers fitted in the New Year.  I have had a bit of time for day dreaming in the last few days as I have been doing a rather dull task, this has resulted in another dilema. 

 

I have 33" tyres and I have no plans to go bigger currently, but I am wondering whether I need to think about the small chance I decide to go up to 35" tyres. My understanding is that anything above 33s and I will need chromoly shafts in the Dana 30 at the front of my TJ. As I am fitting the ARBs in the near future then I need to decide between two options:

1) a 27 spline locker, in which case I can run with the stock shafts for now and may never incur the cost of going to chromoly, but will be limited to 27 spline inner shafts if I do ever upgrade

2) the 30 spline locker, in which case I will need to spend on upgrading to 30 spline chromoly inner shafts now but will be future proofed if I do ever go to 35s

I have read the 30 spline is something like 40% stronger than the 27 spline, is that the sort of number people recognise? Is the increase in strength a real word benefit in my situation, or is there likely to be a weaker link that will give way before a 30 spline inner? For example, with 30 spline inner and 27 spline outer is the outer shaft likely to break before the inner in most situations? Has anybody gone so far as to also run 30 spline outers?

Another thought I have is that staying at 27 spline inner and outer will mean I would still have spare shafts (in the form of the OEM ones that would get taken out) in a situation where I do break one. The risk is I break a 30 spline shaft and then have to wait months for one to come in to stock and ship to the UK.

Any thoughts much appreciated?

[V]

I run 30 spline inners and outers with spindles on my 2001 XJ with 35" tyres. The 1993 on 33" tyres is OEM 27 spline inners and outers with unit bearings. I am building a high pinion D30 with 30 spline inners, outers and spindles for the 1993 but the cost is horrendous. I have considered running 27 spline outers and unit bearings when it goes up to 35" tyres as a stepping-stone upgrade.

 

The drive rings in my free wheeling hubs were sold by WARN as 'Hub Fuses'. They are simply drive rings with part of the teeth machined off to tune the shear strength to be just below the failure point of a Spicer 760 u-joint. I have never had a problem with my 30-spline chromoly shafts, the 760 u-joints or the hub fuses. The only fault repairs I have had to do in my front axle have been seal failures and a broken cap screw in one of the WARN hubs.

 

I think the most likely failure of a 30-spline shaft in the UK will be a u-joint break that damages an axle shaft ear. Your options are:

1. Have a spare set of 30-spline inners with or without assembled outers

2. Contact a UK driveshaft manufacturer to see if they can custom make a replacement shaft or friction weld a Frankenstein shaft from the usable part of the 30-spline shaft and another shaft with suitable ears.

3. Order a custom 30-spline shaft from Moser in the USA

4. Order an off the shelf/wait for stock shaft from Yukon

5. Upgrade to a 30-spline RCV shaft set with appropriate outers

6. Downgrade to a 27-spline diff temporarily

7. Temporarily swap in a 27-spline D30 axle housing assembly with the same gear ratio

 

I run 30-spline outers for the bigger wheel bearings that go with spindle hubs. They have much longer mileage compared to running tiny unit bearings with big tyres. Wheel bearing wear can lead to accelerated u-joint wear and failure of the u-joint and axle shaft. Some people like unit bearings for their ease of replacement. I prefer the long term reliability of bigger spindles as I have less problems with my 35" XJ than my 33" XJ with unit bearings.

 

Another benefit of spindles with free wheeling hubs is that you can unlock them and allow your axle shafts, diff and front propshaft to remain stationary while driving in 2wd. My heavy Jeep usually averages 16mpg in 4wd, up to 17mpg in 2wd with the hubs locked. However, I have started using the freewheeling hubs since Christmas and noticed I can achieve up to 24mpg on cruise at 60mph on the flat. I think regular use of my freewheeling hubs could improve the 2wd average to 18-20mpg which is not bad for a 4.0L Jeep that weighs 2200kg.

 

I have a friend that rock crawled a modified XJ with heavy 35" Maxxis Creepy Crawler cross-ply tyres on OEM 27 spline shafts and unit bearings with an ARB. He always carried fully assembled spare axle shafts (used recon) and new unit bearings and treated them as disposable parts. Breakages are not a problem if you have ready assembled spares and the tools to swap them in on the trail.

 

[V]

 

[digger]

Hi V, it never ceases to amaze me what can be done. 

One machine I built with a V8 added to an alien gearbox kept destroying the clutch.  Borg warner supplied a Ferrari clutch with a special centre plate. They had  bored out the centre plate ,then cut the correct splines as a tube  from one I supplied, which was turned down to fit in the bored out plate. They then welded it right through, only telling me  ''its a special process!''  I've always wondered how they did it?  I think you've just answered the question!

Edited January 2 by digger

[digger]

Hi Uktj,

The thing to consider is  ''I have no plans to.....''

I have made this mistake and so have a lot of other folk!  In my case I wish to be able to return the YJ to stock if necessary because they are now so rare and in need of preservation.  Additionally every day I get older  I get less inclined to do any more, I just want to have fun!

Following this I did everything to go 31" , OME lift complete etc etc. The gearing was poor so I regeared etc etc. Really good but ''perhaps I should have bigger tyres! Now I'm stuck with 33s unless I do it all over again!

Which rear axle do you have? I had Dana 35 and found out that it was a lot weaker than the HP D30 in the front!

Hind sight is a wonderful thing!

Edited January 2 by digger

[V]

1 hour ago, digger said:

In my case I wish to be able to return the YJ to stock if necessary

There is probably no need to do this based on CJ values in Europe. It is practically impossible to find a factory original CJ. The authorities have no idea what correct suspension height is so many have small suspension lifts that are declared as stock 'old timers'.

 

I think everything about car values will change in the run up to 2030. I think the important thing is to keep your Jeep running and use it while you can.

[TimC]

5 hours ago, V said:

I think the important thing is to keep your Jeep running and use it while you can.

Amen to that!

[UKTJ]

5 hours ago, digger said:

Hi Uktj,

The thing to consider is  ''I have no plans to.....''

I have made this mistake and so have a lot of other folk!  In my case I wish to be able to return the YJ to stock if necessary because they are now so rare and in need of preservation.  Additionally every day I get older  I get less inclined to do any more, I just want to have fun!

Following this I did everything to go 31" , OME lift complete etc etc. The gearing was poor so I regeared etc etc. Really good but ''perhaps I should have bigger tyres! Now I'm stuck with 33s unless I do it all over again!

Which rear axle do you have? I had Dana 35 and found out that it was a lot weaker than the HP D30 in the front!

Hind sight is a wonderful thing!

Hi @digger

 

That is fair comment, what is a small chance now can always become exactly what one wants.  I have a Dana 44 in the rear along with the Dana 30 in the front (standard export TJ configuration I believe).  The general view on the US TJ forum I frequent is that with that combo it is reasonable to run 35s if you fit 27 spline chromoly shafts in the front Dana 30.  Going above 35s is considered to be the point where a complete change of axles from the stock dana 30 / dana 44 combo is required.  

 

Clearly 30 spline chromoly shafts would be stronger and reduce the risk of breakage even further, but most I have spoken to online seem to get away with 27 spline the vast majority of the time*.  I also have to be completely honest and say that, even after a bit of time looking online, my understanding of the spindle hubs @V refers to is rudemantary at best.  I don't recall seeing them on the usual parts sites such as Quadratec and Morris 4x4, so maybe they are something that needs to be specially made.

 

For me the ease of sourcing 27 spline shafts and the fact the old OEM shafts I would be replacing with chromoly ones would be a first set of spares does seem very helpful, as it means I could carry a spare set and the TJ would not be off the road while I had to wait for a replacement 30 spline to come from the US - albeit the chance of needing a replacement would be reduced.  I reognise all the options for dealing with a 30 spline breakage @V highlights above, but the reality is that the chances of me changing differentials or axles if I break something are negligable.  Where I think I am ending up on this is that I will accept the higher chance of breakage of a 27 spline as a trade off with the greater ease of dealing with a breakage, especially as at the moment with 33s.

 

Tying in with another thread @V initiated in October, as I am hoping to regear soon anyway, I am though still thinking about switching out the current LP dana 30 for a HP dana 30 from an XJ**.  The key benefits from my perspective are: added strength in the ring and pinion reducing the chance of breakage, and, the improvement in driveshaft angle which may give scope to either, potentially change the transfer case skid to get a bit more clearance there, or get a bit more lift by adding some spacers to the current OME springs.  Obviously both of these could be done anyway, but that would then almost certainly require fitting an SYE and new driveshaft which would not give the extra strength the HP 30 would.  The downsides to this part of the plan are: if I understand correctly I would need to switch to (at a minimum) adjustable lower control arms in the front at the same time, and, it makes buying new gears a bit less convenient as I can't see simple all in one kits for a reverse dana 30 and a dana 44 (presumably the XJs never came with that axle combination).

 

But I still have plenty of time to change my mind, as I still need to find somewhere to do the regear / lockers anyway.

 

 

* The majority of the US TJ owners I chat to online are based in California, Arizona, etc. so they are focussed very much on rock crawling and rarely see any mud.  Whether the prevailing conditions here have a big impact on the 'prevailing wisdom' is something I just don't know.

 

** I see reference to vacuum disconnect axles and the best option being to find one that never had this feature.  Is that detrmined by the year of manufacture, or do I need to look out for something else to tell me if this is an issue with a particular axle?

[digger]

5 hours ago, V said:

 

 

I think everything about car values will change in the run up to 2030. I think the important thing is to keep your Jeep running and use it while you can.

I've always thought car values and depreciation is a scam here , especially when in countries such as France when I was there, used cars were (are?) valued almost entirely on their condition etc, age playing only a small part. I don't know about Jeep values on the continent, are they up?

Having said that, I agree with you  . I think there is a grave risk that any 'disliked ' cars for whatever reason could be penalised in a variety of ways resulting in chronic depreciation  and ultimately their worthless destruction. Let's face it there is no party that hasn't taken opportunity to penalise the motorist! 

However ,I find it difficult to believe that classic and  historic race cars etc will be hit in the same way. There are a large number of people, some with an awful lot of money and influence who participate in these pastimes. Can one imagine electrifying an 'E ' type Jaguar  for example or their owners accepting that they will be confined to a museum. I can't and its one of the reasons I love my YJ along with XJs, CJs etc. 

Besides which, we all know that whilst some cars may be especially bad polluters, man's  cars are only a tiny contribution to global warming and that there are far worse things that man has done, such as the destruction of trees!

[UKTJ]

28 minutes ago, UKTJ said:

...The downsides to this part of the plan are: if I understand correctly I would need to switch to (at a minimum) adjustable lower control arms in the front at the same time, and, it makes buying new gears a bit less convenient as I can't see simple all in one kits for a reverse dana 30 and a dana 44 (presumably the XJs never came with that axle combination)...

 

 

Scratch that, down to my error, have found all in one kits for reverse dana 30 front / dana 44 rear now - assuming the dana 44 rear in a 1987 - 96 XJ is the same as that in a 1997 - 2006 TJ.

[digger]

16 minutes ago, UKTJ said:

 

 

 

* The majority of the US TJ owners I chat to online are based in California, Arizona, etc. so they are focussed very much on rock crawling and rarely see any mud.  Whether the prevailing conditions here have a big impact on the 'prevailing wisdom' is something I just don't know.

 

** I see reference to vacuum disconnect axles and the best option being to find one that never had this feature.  Is that detrmined by the year of manufacture, or do I need to look out for something else to tell me if this is an issue with a particular axle?

Hi UKTJ,

Much of your thinking is similar to mine. Hence for example I only fitted Chrome Molys because I wanted to reduce the chance of hassle caused by breakdown issues which I had already experienced. I am unlikely to do lots of rock crawling etc and more often than not its wet and greasy.  I just want to minimise future work because of my age !

I think Vacuum disconnects are only in Yjs and early XJs. I have removed mine because I could see that it was a weak spot in the axle, although it wasn't that that broke! The new shafts only come in one piece anyway! It probably slightly weakens the casing but its not something I'm worried about with what I do and besides one could always brace the axle case in some way.  The Xj that I took my  axle bits from was a'98 and it did not have a disconnect in the front D30.

[digger]

I THOUGHT  that only a few lucky TJs had D44 and rest D35 but I may be wrong. Certainly D44s are hard to come by. YJ rears only had D35. That's why I fitted the Chrysler 8.25 29 spline when it was going. I THINK many later XJs had the 8.25 but usually 27 spline!  My research suggested the 29 spline (commercial) was as strong as a D44 except it had the draw back of 'C' clips which didn't bother me. Its certainly massive construction compared to the D35 I removed.

A lot of Jeeps seem almost 'hand built ' in the factory utilising whatever parts /axles were available at the minute!  There's a lot of things about my YJ for example that must be original but do not fit any 'stock' specification that I have found!  Eg , I have a 'safari' interior' but no aircon in what purports to be a 'LTD'.

Jim O, bless him, confirmed this to me a number of times.

Edited January 2 by digger

[UKTJ]

56 minutes ago, digger said:

I THOUGHT  that only a few lucky TJs had D44 and rest D35 but I may be wrong. Certainly D44s are hard to come by. YJ rears only had D35. That's why I fitted the Chrysler 8.25 29 spline when it was going. I THINK many later XJs had the 8.25 but usually 27 spline!  My research suggested the 29 spline (commercial) was as strong as a D44 except it had the draw back of 'C' clips which didn't bother me. Its certainly massive construction compared to the D35 I removed.

A lot of Jeeps seem almost 'hand built ' in the factory utilising whatever parts /axles were available at the minute!  There's a lot of things about my YJ for example that must be original but do not fit any 'stock' specification that I have found!  Eg , I have a 'safari' interior' but no aircon in what purports to be a 'LTD'.

Jim O, bless him, confirmed this to me a number of times.

My understanding is that in many specifications in the US the D35 was standard and the D44 was an option at the back of the TJ, but for export to RHD markets (Australia, Japan and UK) the D44 was fitted as standard.

 

It does not surprise me that there is a lot of 'variation' between builds of older Jeeps - especially ones for export where the volumes would presumably be much lower.  Mine claims to be a special edition, but over and above some stickers that seems to simply mean using up some left over XJ wheels, seats from the previous year's 60th Anniversary TJ and probably a few other odds and ends that were hanging around in some parts bins.  I always refer to it as a special 'addition' for that reason.

[V]

2 hours ago, UKTJ said:

My understanding is that in many specifications in the US the D35 was standard and the D44 was an option at the back of the TJ, but for export to RHD markets (Australia, Japan and UK) the D44 was fitted as standard.

Correct. All UK TJ Wranglers have a D44 rear axle. The early ones had drum brakes, the later models had disc brakes.

 

3 hours ago, digger said:

I think Vacuum disconnects are only in Yjs and early XJs.

All of the UK spec RHD XJ Cherokees had the stronger front axle without the disconnect and with bigger u-joints than the YJ.

 

4 hours ago, UKTJ said:

I also have to be completely honest and say that, even after a bit of time looking online, my understanding of the spindle hubs @V refers to is rudemantary at best.  I don't recall seeing them on the usual parts sites such as Quadratec and Morris 4x4, so maybe they are something that needs to be specially made.

This is the 30-spline spindle hub kit I will be using on the next build on my '93 which is similar to the discontinued WARN 38109 kit that I currently have on my '01.

https://www.yukongear.com/shop/ya-wu-08

[UKTJ]

1 hour ago, V said:

Correct. All UK TJ Wranglers have a D44 rear axle. The early ones had drum brakes, the later models had disc brakes.

 

All of the UK spec RHD XJ Cherokees had the stronger front axle without the disconnect and with bigger u-joints than the YJ.

 

This is the 30-spline spindle hub kit I will be using on the next build on my '93 which is similar to the discontinued WARN 38109 kit that I currently have on my '01.

https://www.yukongear.com/shop/ya-wu-08

Ah, OK, I have seen those kits referenced, maybe I just never understood the mechanics of them before.  My education continues!

[V]

There are two forms of spindle kits for the XJ, YJ, ZJ, TJ:

1. Kits with 5 studs on 4.5" PCD for original equipment wheels
2. Kits with 5 studs on 5.5" PCD needs new wheels with CJ stud pattern

The 4.5" usually have 27-spline shafts, small wheel bearings, external/integrated hub locks. Stronger than stock unit bearings, fuel economy of freewheeling hubs, a small but worthwhile strength upgrade for off-road on 33" tyres. Traditionally popular with those that want to flat tow a Jeep on stock wheels.

 

The 5.5" usually have 30-spline shafts, big wheel bearings with a wide spacing for 35"-37" tyres, separate internal hub locks. Overall, same benefits as the smaller 4.5" plus added strength of ChroMo D44 shafts and stronger internal hub locks. The downside of the stronger bearings is your Jeep needs bigger PCD wheels to fit them, not a problem if you are already buying new 8" wide wheels for the tyres. The rear axle will either need PCD adaptors or dual stud pattern axle shafts and brake discs.

Edited January 2 by V

[UKTJ]

On 02/01/2023 at 17:07, UKTJ said:

...switching out the current LP dana 30 for a HP dana 30 from an XJ**.  The key benefits from my perspective are: added strength in the ring and pinion reducing the chance of breakage, and, the improvement in driveshaft angle which may give scope to either, potentially change the transfer case skid to get a bit more clearance there, or get a bit more lift by adding some spacers to the current OME springs.  Obviously both of these could be done anyway, but that would then almost certainly require fitting an SYE and new driveshaft which would not give the extra strength the HP 30 would.  The downsides to this part of the plan are: if I understand correctly I would need to switch to (at a minimum) adjustable lower control arms in the front at the same time...

OK, I was clearly tying myself in knots (and maybe I still am), but a HP diff in the front will do absolutely nothing for rear driveshaft angle.  I was talking rubbish when I suggested it would.  There will be a reduction in front driveshaft angle, but that will help in any way re a 'tummy tuck' or lift.  Front drive shaft angle also gets more complicated from my most recent reading, given the interplay with caster and I do not yet understand how HP versus LP plays into that.

 

Therrfore the question really becomes one of added strength in the ring and pinion and if that justifies the cost of the switch.  For me I think the factors to quantify are:

The cost of the HP dana 30 (c.£300 from what I see on eBay)

Plus the cost of upgrading at the very least the front lower control arms to adjustable ones (realistically at least £200)

Less the sale of the LP axle or the value of the spares retained

[V]

The adjustable length control arms provide the ability to change the pinion angle on the front axle. If your Jeep experiences some undesirable driveline vibration, the control arm length can be changed to raise or lower the pinion accordingly. However, by doing so you are also naturally rotating the axle on the axis of the wheels. As castor is fixed by the angle of the ball joints in the knuckles, rotating the axle to correct the pinion angle can effect castor.

 

Cutting the knuckles off the axle to re-weld them with axle tube sleeves is the correct way to get the perfect pinion and castor angle for the new suspension geometry. Adjustable control arms are often considered the easy way to get a good enough result.

[frosty]

i have adjustable upper and lower arms back and front, on my JK 2 DR, they are essential at the rear to get an acceptable drive line angle after a 4-inch lift, as the prop shaft as it is very short.  As vince says, they allow you to get an acceptable level of steering geometry on the front end too.