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permanent 4wd on a series


Tonk
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i know that most people i have spoke to are under the opinion that a series landrover cant run in permanent 4wd like a defender does because of the uj's in the front halfshafts, but no one to date has come up with a reason why this is so.

can anyone explain why not? and back it up with some facts?

TIA

Mark.

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Tonk - ***this is a guess*** ...

I would ASS-ume it's because of the non-uniform angular velocity of a single UJ when one side is driven at a constant rate and the joint has a non-zero angle of deflection?

The 'constant velocity' joint (I think) is designed to give constant rotation rate (assuming input is constant) at varying degrees of angle (turn angles), the only way you get this with a UJ is to have zero turn angle, so every timeyou turn the wheels, they will be driven at a sinusoidally varying speed. You may not care if road miles are low, but er... you might?

Could set up odd vibrations I guess. I also suppose tyre life would be reduced and stresses on the joints increased.

Doesn't TI Console do a CV replacement kit for series axles?

Cheers, Al.

[Cue Fridge to come and 'set me straight'... :rolleyes: ]

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Let me try and explane in simple terms, did you ever try 4wd in a series on a hard surface? the steering kicks you back trying to go back in the straight ahead position as the uj's try to go back inline. The same happens on the road when in permanent 4. Its a real pain round corners :angry: especially with no power steering and a powerful engine. I tried it for a while and i had enough of fighting the wheel at every corner so i went to stage 1 cv's. In a straight line or with minor steering input its the same as anyother landy, try full lock and you get the jives! :P

Its all to do with the uj's as there is a difference in rotational speed as the short stub trys to accelerate and decelerate while applying power. This would be cancelled if both shafts where to come into phase like a propshaft but the diff does not permit this, unless difflocked! and unrecommended for road use if you like going in a straight line........................ :D

The whole effect is transmitted trough the steering system in someway thus making it a pig to drive.

If anybody is going with a permanent box in a series i do recommend that converting it to run in 2wd is a better and easier option then going with the cv's, unless you are lucky to find an complete axle.

Grem

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The biggest and most important difference is in the centre diff. The Series vehicles don't have one.

On the road the wheels are all going at slightly different speeds, even more so on corners and the diff allows them to rotate at different speeds without stressing the transmission. The diffs in each axle take care of left & right wheels, the centre diff takes care of the difference between front & rear axles. On a Series the two axles are locked together in 4WD which can lead to wind-up and catastrophic damage. Off road it isn't a problem because the wheels slip realtive to one another and speeds are a lot lower.

Difflock on later vehicles does indeed lock the centre diff.

The other consideration is that Series vehicles have UJs at the axle ends, permanent 4WD vehicles have CV joints. With a UJ once the driving and driven flanges are no longer parallel the driveshaft doesn't rotate at a constant speed, thus you get a heavy wobble on the steering. Again not a problem at low speeds, but at road speeds could cause the vehicle to go out of control.

PS

The diff doesn't cause this varying speed, its the fact that there is only 1 UJ at the hub, the drive shaft goes at a constant speed the stub driving the front wheel doesn't unless you're straight ahead.

Edited by rtbarton
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[Cue Fridge to come and 'set me straight'... :rolleyes: ]

ooer :blink:

so what u're saying is when the steering is turned and the uj is say at 45 degrees in rotation to the axle then it would have a slight tight spot cos of 4 points of drive?

cv has about 10 points of drive and is smoother?

hmmmmm

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Well you can't run in Series 4WD, which is the equivalent of Defender centre diff lock, for obvious reasons.

If you mean "can I stick an LT230 in and run permanent 4x4 with the stock open centre diff" then it's a bit vague, I guess LR used CV's for a reason but someone (forget who) pointed out the other day that a lot of yank stuff runs front UJ's and permanent 4x4. But then their UJ's tend to be a bit beefier :rolleyes:

Sorry, that doesn't help much does it :unsure:

Edited to add: CV = Constant Velocity, they don't (AFAIK) have any variation in speed due to turning, hence the name.

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ooer :blink:

so what u're saying is when the steering is turned and the uj is say at 45 degrees in rotation to the axle then it would have a slight tight spot cos of 4 points of drive?

cv has about 10 points of drive and is smoother?

hmmmmm

No UJs and CVs are different animals. A CV works like 2 UJs back to back. You don't get tight spots, you actually get a change of speed with a UJ.

A propshaft with UJs doesn't rotate at a constant speed, the angle of the driving UJ causes the speed to vary, but the driven UJ evens the speed out again. This is why it is essential to reassamble a propshaft correctly if the sliding joint is split and you need to be aware that you may get vibration if you alter proshaft angles when fitting parabolics &c

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Well you can't run in Series 4WD, which is the equivalent of Defender centre diff lock, for obvious reasons.

obviously, both would wind the transmission up

If you mean "can I stick an LT230 in and run permanent 4x4 with the stock open centre diff" then it's a bit vague, I guess LR used CV's for a reason but someone (forget who) pointed out the other day that a lot of yank stuff runs front UJ's and permanent 4x4. But then their UJ's tend to be a bit beefier :rolleyes:

Sorry, that doesn't help much does it :unsure:

Edited to add: CV = Constant Velocity, they don't (AFAIK) have any variation in speed due to turning, hence the name.

hmmmm got your 2wd lt230 up and running yet jon? :lol::lol::lol: stoopid question :ph34r:

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so what u're saying is when the steering is turned and the uj is say at 45 degrees in rotation to the axle then it would have a slight tight spot cos of 4 points of drive?

cv has about 10 points of drive and is smoother?

Mmmm... I see what you're thinking but that's not really the reason. It's not that the CV joint has (for example) 10 smaller velocity oscillations per revolution, and so the effect is less noticeable. It is simple that the CV has an input/output rotation rate ratio of 1 for any angle of 'steer'. There isn't any vibration in that sense.

By nature of it's geometry (the fixed orthogonality of the bearing caps I think - as opposed to the relative 'freedom' of tha balls in a CV joint), the UJ has no choice but to vary its output rotational velocity for a fixed input rate. The magnitude of variation might change with steer angle, but it's always there.

This is why double cardan propshafts use 2 UJs to cancel out each other's rotation rate variation.

As John points out - plenty of trucks run UJs in front though...! Maybe run it and see how you like it.

Anyway - what are you planning with all this gearbox removal / CV discussion?...

Intrigued... Al.

:)

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ah i see your point,

i have driven my series home many a time in front wheel drive, due to errrrr the rear axle being in many broken pieces and have suffered no problems, sayin that it was only for short 40 mile journeys.

the problems must still be there though when 4wd is engaged, or does it just put up with it for short periods, or is the effect lessoned cos of less grippage of the tyres?

so many questions........

swapping out my box is a long story, oh and i'm mad :D

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Tonk

If you piting a LT230 in why not fit some Yank axles they should take the canning

in the short turn take the rear prop off and see how it drives in 4wd.

Also this may not work but what about auto hubs reduceing the wind up

Edited to say

bugger you have already trid that...

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ah i see your point,

i have driven my series home many a time in front wheel drive, due to errrrr the rear axle being in many broken pieces and have suffered no problems, sayin that it was only for short 40 mile journeys.

the problems must still be there though when 4wd is engaged, or does it just put up with it for short periods, or is the effect lessoned cos of less grippage of the tyres?

so many questions........

swapping out my box is a long story, oh and i'm mad :D

M, I think the main problem is the lack of a centre diff on a series t.box. If you've had no issues driving home with front wheel drive only then I guess you'll probably be OK with perm 4WD and a centre diff. As others have said, loads of Yank stuff runs like this.

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A friend in Headley has a Series 1 with VM diesel and permanent 4 wheel drive box.

Hes run it for years and no ill effects, haven't driven it myself but been in it and it feels OK.

Doesn't do high speed much but I know he's been to Wales so can't be that bad.

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Let me try and explane in simple terms, did you ever try 4wd in a series on a hard surface? the steering kicks you back trying to go back in the straight ahead position as the uj's try to go back inline. The same happens on the road when in permanent 4. Its a real pain round corners :angry: especially with no power steering and a powerful engine. I tried it for a while and i had enough of fighting the wheel at every corner so i went to stage 1 cv's. In a straight line or with minor steering input its the same as anyother landy, try full lock and you get the jives! :P

Grem

and if it has power steering?

series front axle internals still rotate when in rear wheel drive anyway, although there is no power being put through it.

i dont know if i'm talking myself into it or out of it now :rolleyes:

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that is a possibilty but he has fitted his kit :rolleyes:

maybe i should go take a centre diff apart........

so next question is, would they be premature wear if a centre diff would be putting the power out of the rear most of the time?

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Cheeky gits! <_<

As discussed the other day, I doubt converting an LT230 to 2WD would take Tonk more than a couple of lunch breaks, there's really naff all to it. Also I don't think any premature wear would ocurr, in fact as you're locking or removing the spider & gears there is less to go wrong.

Tonk, did I send you the scans of the conversion kit manual?

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There is no reason not to run permanent 4wd on the road in any vehicle with a centre diff.

My 2a with lt230 and series axles drives great.There is a barely noticable wobble of the steering wheel if you take a corner fast on full lock.

The issue is just the strength of the ujs.But it has to be said that standard cv joints break pretty often too.

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I know what happens when you do drive a s3 on the road in 4wd . I left my old one in 4wd for a week on the road. Wondered why it was a pig to turn going up and down the multi story car park in winchester. Finally the rear prop broke and the front. mmm that was fun at 50 mph. Thought and sounded like i had just ran over the front axle. Not somthing i want to try again

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