VCU ponderings of a tinkering minkerton

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DD3 said:
One of the main issue with the VCU technology, as highlighted by this and other threads is that nobody really knows what its operating perimeters are. When does it cut in / out, how much drive front to back. It is this inherent lack of sophistication that has consigned it to motoring history - how can we have a conversation comparing experience when say my VCU is used and yours is recon and the next is brand new OE. More modern systems remove most of this speculation. My experience of VCU drive is that it will engage and get you out of trouble but without the finesse of modern systems, which work better both on and off tarmac. I say this as someone who hates stuff like parking sensors and electric handbrakes, just more to go wrong, but credit where it is due. Just my take.
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it worked exceedingly well in the rr ,and does in the fl its only the reduction in rwd that gives it an issue ,it works harder so life is reduced compared to rr
 
The Mad Hat Man said:
the X-Trail (the only slitty that I am familiar with) has the following system - basically its an electronic VCU fixed to the nose of the diff.


1724d1173567880-rear-sub-frame-removal-4wd2.jpg


1725d1173567880-rear-sub-frame-removal-4wd-clutch.jpg


1726d1173567880-rear-sub-frame-removal-diff.jpg



you might like to peruse these posts - 1 - 2 - 3 - 4
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ideas....
 
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difflock has no reaction time just physical lock ,the advantage is having drive to both axles while still been able to steer without geting excessive wind up ,though through viscous the system has allways some wind up but manageable by the vehicle running gear until it stiffens excessively or seizes
 
jamesmartin said:
difflock has no reaction time just physical lock ,the advantage is having drive to both axles while still been able to steer without geting excessive wind up ,though through viscous the system has allways some wind up but manageable by the vehicle running gear until it stiffens excessively or seizes
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yes it does, James - you have to remember to engage difflock :rolly:.

a VCU or an electronic version can be always "engaged", without suffering wind-up.
 
The Mad Hat Man said:
yes it does, James - you have to remember to engage difflock :rolly:.

a VCU or an electronic version can be always "engaged", without suffering wind-up.
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the whole point of diff lock is to engage it before getting stuck as its better at keeping you going that getting you out ,god off road drivers would know that ,so point still stands , reactionary diff locking systems as used in tractors etc since the 80s is obviously better as steering isnt effected and torque distribution can be altered per wheel and can apply to all 4 wheels , t/c is good but only works on braking opposite wheel so is limited somewhat
 
Haldex 3rd Generation as fitted to FL2 - 'The result is used exclusively on Freelander 2, and pre-emptively engages four-wheel drive quickly and completely. An improved high-pressure pre-charge pump charges the hydraulic system as soon as the engine is started, allowing for full-time 4x4 from rest. It also reduces the time taken to achieve full torque once wheel-slip has been detected – within 15 degrees of wheel-slip rotation (compared with 50 degrees of wheel-slip rotation with the previous generation Haldex). The Freelander 2's Haldex unit is designed to allow up to 1500 Nm of torque transmission. An accumulator also speeds up the unit's response. Full torque transmission can be achieved in 150 milliseconds. In effect, the new Haldex coupling gives the benefits of full-time 4x4 and the efficiency and fuel economy of an on-demand system'.

Personally, I would rather have an on/off switch or lever and dump all the fancy sensors but I dont think this is in LR's development plans.
 
a reactionary system with sensors etc is allways going to be better than 3 locking diffs just from the fact you have drive to all 4 wheels when steering
 
jamesmartin said:
it worked exceedingly well in the rr ,and does in the fl its only the reduction in rwd that gives it an issue ,it works harder so life is reduced compared to rr
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Being on all the time just causes too much stress in the rest of the transmission.
 
jamesmartin said:
only when it stiffens which is bought into been quicker through reduction in drive to rear wheels
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True, but your whole transmission needs to be in top condition to avoid heavy wear down the line. BTW, I'm not anti VCU as such and don't work for Haldex. I just think that switchable 4x4 ie off or on, however supplied, controlled and switched is better.
 
jamesmartin said:
yes i would too ,vcu is better than a center diff lock but not as good as more sophisticated system
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I think we can all aggree on that. Having seen a D3 in action I'm pretty convinced of the merits of the newer systems. But for the price, te FL1 has impressive capability :).
 
WLJayne said:
I think we can all aggree on that. Having seen a D3 in action I'm pretty convinced of the merits of the newer systems. But for the price, te FL1 has impressive capability :).
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Agree - its the ability to switch and have best of both worlds that I'm after.
 
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