I'm planning on making a mechanical replacement for the VCU!

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I described it on the previous page, but here is a photo of a panda box....

DSC01768.jpg


The section on the right is the drive to the rear axle, you can see the lever in the middle for engaging and disengaging the system and a switch to light a warning on the dash when it is engaged.
The complete unit unbolts from the gearbox by 4 bolts. Use a lathe to machine an adaptor so the output end fits to the IRD output flange. You will probably need to make up an end plate where it bolted to the original gearbox to seal it up with an oil seal around the output shaft. You will then need to make up a coupling to fix it to a shortened front propshaft, and some brackets to hold it in place.
 
front wheel drive only until slip is detected and it engages drive to the rear electronically via a coupling - same kind of deal as the new panda 4x4 and a few others on the road.
The old panda system is a simple, basic, robust unit with just a lever to disengage drive that requires no electronics and would be easiest to adapt in this guys case.
 
Sounds terrible to me.

I detailed why in another thread the OP had, but if he wants to try it then good luck to him - I just came across the Panda parts as I stripped my brother in laws one and posted it here for information.
 
You wouldnt need a VCU as well as that dog-clutch, so if it could be manufactured within the length constraints of the VCU , the props could still be used but you would have to replace the VCU with some form of coupling device to take both shafts.
 
I considered that, but if I were doing it, I would prefer to keep the VCU. Without it and the replacement engaged, it would be "locked" 4x4 similar to a disco / Rangie with the centre diff locked or a jap truck in 4x4 - fine in mud, snow etc but no good on grippier surfaces. Discos and Jap stuff have strong enough transfer boxes that they can take a bit of abuse like that but The Freelander would not last very long at all.
Ie driving up a rocky track - being in locked 4x4 is fine while its on gravel etc, but if you get to a bit where its bedrock or something similar then you will have a real problem - a jap truck would cope over short distances but the freelander would ****e its IRD in no time. Disengaging 4x4 at these points is easy to say, but tedious to do and leaves you only with FWD on potentially steep ground - Same goes for winter driving. On a snow covered road, it would be fine while locked, but a clear patch would require you to disengage, then re-engage when you get to another slippy bit - That Panda box cant be switched on the fly so you would have to stop completely each time - tedious and potentially dangerous on the road. But if the VCU is still in place as well, then when the new box is locked, it behaves just like a standard freelander - ie copes well with all conditions and requires no driver input. Then come summertime, he can disengage the panda box and run 2wd with just the pull of a lever.
 
Still sound like a lot of hassle compared to the VCU, which I personally like. I have also driven a lot of miles with a Haldex equipped car, which was very good.

I personally don't want to have to select 4wd, I can't do it as quickly as either of the above systems can. I like that it is there from a standstill. Or on a greasy or muddy road.
 
dave21478 said:
I considered that, but if I were doing it, I would prefer to keep the VCU. Without it and the replacement engaged, it would be "locked" 4x4 similar to a disco / Rangie with the centre diff locked or a jap truck in 4x4 - fine in mud, snow etc but no good on grippier surfaces. Discos and Jap stuff have strong enough transfer boxes that they can take a bit of abuse like that but The Freelander would not last very long at all.
Ie driving up a rocky track - being in locked 4x4 is fine while its on gravel etc, but if you get to a bit where its bedrock or something similar then you will have a real problem - a jap truck would cope over short distances but the freelander would ****e its IRD in no time. Disengaging 4x4 at these points is easy to say, but tedious to do and leaves you only with FWD on potentially steep ground - Same goes for winter driving. On a snow covered road, it would be fine while locked, but a clear patch would require you to disengage, then re-engage when you get to another slippy bit - That Panda box cant be switched on the fly so you would have to stop completely each time - tedious and potentially dangerous on the road. But if the VCU is still in place as well, then when the new box is locked, it behaves just like a standard freelander - ie copes well with all conditions and requires no driver input. Then come summertime, he can disengage the panda box and run 2wd with just the pull of a lever.
Click to expand...

Assuming the VCU is working correctly!!!
 
dave21478 said:
Sounds terrible to me.

I detailed why in another thread the OP had, but if he wants to try it then good luck to him - I just came across the Panda parts as I stripped my brother in laws one and posted it here for information.
Click to expand...
Panda idea i meant sounds good..
Your quick to jump on with a grump argument aint ya..
 
dave21478 said:
I considered that, but if I were doing it, I would prefer to keep the VCU. Without it and the replacement engaged, it would be "locked" 4x4 similar to a disco / Rangie with the centre diff locked or a jap truck in 4x4 - fine in mud, snow etc but no good on grippier surfaces. Discos and Jap stuff have strong enough transfer boxes that they can take a bit of abuse like that but The Freelander would not last very long at all.
Ie driving up a rocky track - being in locked 4x4 is fine while its on gravel etc, but if you get to a bit where its bedrock or something similar then you will have a real problem - a jap truck would cope over short distances but the freelander would ****e its IRD in no time. Disengaging 4x4 at these points is easy to say, but tedious to do and leaves you only with FWD on potentially steep ground - Same goes for winter driving. On a snow covered road, it would be fine while locked, but a clear patch would require you to disengage, then re-engage when you get to another slippy bit - That Panda box cant be switched on the fly so you would have to stop completely each time - tedious and potentially dangerous on the road. But if the VCU is still in place as well, then when the new box is locked, it behaves just like a standard freelander - ie copes well with all conditions and requires no driver input. Then come summertime, he can disengage the panda box and run 2wd with just the pull of a lever.
Click to expand...

I completely agree with this analysis. I often drive a local beach for fishing. In the Disco1 when I left the road and went onto the sand I had to stop and put it in diff lock and then take it out of diff lock once back to the road. With the Freelander there's nothing to do - the car, or rather VCU, takes care of it all - in concept and use its VERY good. The problems come with the reliability of the VCU and its ability to cause drastic problems when something's not in perfect working condition. The ability to disengage it at times its not likely to be of benefit would eliminate the risks while still giving the benefits at times when its likely to be of use.

I'm not sure you could disengage the VCU though without causing damage to it. Basically you'd be putting something like an "on/off" gearbox/clutch on the back of the IRD or rear diff (and shortning one of the props). When "off" that prop would not have drive but the other would - therefore the VCU would be permanently engaged/hot. I have no understanding of what this would do to it, but I guess it would damage its ability to slip/lock as intended when put back to "proper" use. If you didn't want to damage it, you'd have to put a gearbox/clutch in at both ends to disengage the whole prop/VCU assembly - if the task wasn't difficult/mad enough before, surely it would be having to double everything up!

An alternative would be a 'guage' on the dash to show how "locked" the VCU is. That way you could monitor when the VCU is kicking in when it shouldn't and thus have an indicator that something's up and the VCU should be checked/replaced.
 
GrumpyGel said:
An alternative would be a 'guage' on the dash to show how "locked" the VCU is. That way you could monitor when the VCU is kicking in when it shouldn't and thus have an indicator that something's up and the VCU should be checked/replaced.
Click to expand...

easy enough to do - monitor speed of both halves of VCU and use a comparitor to check difference in rotational speed. use that to trigger an LED or voltmeter.
 
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The Mad Hat Man said:
easy enough to do - monitor speed of both halves of VCU and use a comparitor to check difference in rotational speed. use that to trigger an LED or voltmeter.
Click to expand...

What benefit would that be?

At times the VCU should slip, others not - whether its slipping or not is not the issue - its whether its not slipping when it should that is the issue? eg reverse full lock - the VCU shouldn't put up too much resistance but problems start when it does?

It needs more like a pressure sensor or the IRD crown wheel. In the reverse fuill lock - if it goes up a bit that's OK, but if it goes way up then there's issues. Driving along straight, if there's any pressure showing, check tyres. etc.
 
GrumpyGel said:
What benefit would that be?

At times the VCU should slip, others not - whether its slipping or not is not the issue - its whether its not slipping when it should that is the issue? eg reverse full lock - the VCU shouldn't put up too much resistance but problems start when it does?

It needs more like a pressure sensor or the IRD crown wheel. In the reverse fuill lock - if it goes up a bit that's OK, but if it goes way up then there's issues. Driving along straight, if there's any pressure showing, check tyres. etc.
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because when it hardly slips, or always slips. it would show up. constant low slippage would be a sign of problems. if the slippage varies substantially, then the VCU is good. it is te variation that is significant.
 
MHM is right. The VCU should always slip unless the front wheels lose traction, at which point you would probably be aware of it.
If you set your led or whatever so it lights when the rotation is virtually the same, you know that either your rear wheels are being driven or you are destroying your IRD, which is what you want to know surely?
So if it's lit up on the motorway you can suspect a problem.
 
I supose slip difference would also give you an indication - if its not slipping (no LED lit) on reverse full lock then in effect there is too much pressure. If it is slipping driving straight then check tyres. But if tyre pressure was down and the VCU "locked" then no slippage would show but there is a problem.
 
I wont for one minute pretend i know what is going on here lol i have a slight bit of mechanical knowledge and understand what is being said slightly but have no input at all just like to read though waiting for the guy that started this topic to get back to everyone to let us know how he got on and see what everyone thinks of his idea, if any
 
The Mad Hat Man said:
no it wouldnt - ir wouldnt show a VCU that fails in an unlockable condition.
Click to expand...

Pressure would give a much better indicator than testing slippage. eg Reverse rear lock on a good VCU would show slippage and some pressure, where as with a nonlockable VCU it would show the same slippage but would show no/reduced pressure.

Unlockable VCUs are not the primary problem - they don't cause very expensive repair bills, but I agree they could leave you stranded.

DaddyCoolJordan said:
waiting for the guy that started this topic to get back to everyone to let us know how he got on and see what everyone thinks of his idea, if any
Click to expand...

There have been various threads on this topic - they are all pretty academic really. I don't think anyone has or is likely to build anything to replace the VCU (definitely for the masses) - too complex/expensive. But its very interesting discussing it :)
 
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