VCU, IRD, what the...?!

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LewisH

LewisH

New Member
Posts
25
Location
Lewisham, SE London
Hi,

I've been on and off here for a while now.

Was orignally looking at getting a Defender, but I just think its a little too impractical for me.

ANyway, I'm looking at getting a Td4 Freelander, probably around the 2000 - 2002 age.

I keep seeing posts about VCU failures and IRD's but dont have a clue what to look for to decipher all this info. I search for 'tippex test' and it simply returns lots of posts telling you to search for 'tippex test'! :doh:

Anyone care to enlighten me as to what I'm letting myself in for? :confused:

Thanks! :D
 
Freelanders have a design fault in their drive train which means that the VCU fails after a period of time. The gel in the VCU seems to harden, not sure why and this ultimately leads to the VCU seizing up and locking front and rear axles with nasty consequences. The tippex test is one way to see if the VCU has seized and may help you spot a dud before it costs you a lot of money.

Before it seizes though it can still wreak havoc as it puts more strain on the remainder of the drive train, requiring more power to work.

The answer - having avoided a bad one - is to probably treat the VCU with some care. Test it regularly and even consider replacing it after some set mileage.

Hope that helps

Chris
 
IRD is the front differential, FD is the rear differential. VCU is a viscous coupling unit that allows slip between the two prop shafts. Drive is given to the front wheels only, when the front wheels lose traction the VCU stops slipping, locks up and the drive is also sent to the rear wheels, ie 4wd is engaged. If you drive everywhere in 4wd you will wear out the drivetrain very quickly, ie bugger the IRD and FD.
To check that the VCU is slipping the tippex test is done. Do this by putting a blob on each prop in line with each other, go for a drive on the road. The two blobs should no longer be inline if the two props are spinning at different rates, ie the VCU is slipping. If the two blobs are still in line then assume the VCU is siezed.
 
Snifflebag said:
Freelanders have a design fault in their drive train which means that the VCU fails after a period of time. The gel in the VCU seems to harden, not sure why and this ultimately leads to the VCU seizing up and locking front and rear axles with nasty consequences. The tippex test is one way to see if the VCU has seized and may help you spot a dud before it costs you a lot of money.

Before it seizes though it can still wreak havoc as it puts more strain on the remainder of the drive train, requiring more power to work.

The answer - having avoided a bad one - is to probably treat the VCU with some care. Test it regularly and even consider replacing it after some set mileage.

Hope that helps

Chris
Click to expand...

Its not a design fault its just that VCUs wear out like any other component, and as it is a sealed unit there is nothing you can do about it other than change it.
 
hello...
Howardo, your test is very interesting to do, unluckily i cannot understand it because of my bad english (i am a french)...may you please join a photo where the blobs have to be put ?
Okay i am asking a lot i know...apologize...and thank you anyway for your description
 
Put the tippex where the yellow dots are shown .When you go for a drive do a couple of tight turns forward and in reverse ,if the marks are out of line after driving the car for a while then the VCU is ok.
vcutest-1.jpg
 
Ah cool. Thanks for that. Makes more sense.

Looking at the threads I'm guessing the Td4 is the one to go for. Do the older diesels cause as much grief as the K series petrol engines? I'm wondering if I should spend a little less on the car and have some spare cash for the VCU and other 'niggles'.
 
LewisH said:
Ah cool. Thanks for that. Makes more sense.

Looking at the threads I'm guessing the Td4 is the one to go for. Do the older diesels cause as much grief as the K series petrol engines? I'm wondering if I should spend a little less on the car and have some spare cash for the VCU and other 'niggles'.
Click to expand...
The older l-series diesel engines can be more reliable than the Td4, but they are slower and more agricultural.
 
this method is very interesting and easy to do..but i am wondering of someone: it does not show if the VCU does force or not, and if it does, how much...what do you think about ?
 
Damn it!

I just knew I shouldn't have gone to my local dealer today!

Whilst the FL2 is lush, it's seems HUGE compared to the FL1, also a little to 'bling'.

Decided I'd be better off coughing up the extra couple of grand for a FL1 facelift and ensure I replace the VCU.

I'm guessing as the basics of the car are the same in both guises that the well documented problems are inherent to the facelift model as well?
 
howardo said:
Visit this web site, it has some info on the VCU and testing of it.

Home - Bell Engineering
Click to expand...


Thats us.

The Tipex test is complete bullsh*t, it proves nothing. VCU's never seize solid, if they did the car could not move at all. They basically get tighter. The tighter they get the more wear they cause on the transmission line causing the ird and diff to fail.

Few basic checks:-
  1. Check it has a prop shaft
  2. reverse it on full lock, if it comes to an abrupt halt the vcu is knackered. There will be some resitance but should not be blindly obvious
  3. if it clonks let on and off the power could be IRD or could be rear diff mounts or both
  4. check state and size of front and rear tyres, they all need to be the same with the same amount of wear, if they are different they will have put extra wear on VCU
  5. check inside edge of rear tyres, if they have a saw tooth pattern VCU is not the best
  6. If its done over 60k and not had a VCU factor in changing it as a precautionary measure, treat it lke a cam belt
  7. Check for leaks from rear diff and offside front driveshaft where it exits the IRD
  8. Check for play in front drive shaft inner CV joint and where it goes into IRD

There are lots of other things to check, look at the website for a bit more info, plus all the usual stuff when buying any car
 
austen said:
Thats us.

The Tipex test is complete bullsh*t, it proves nothing. VCU's never seize solid, if they did the car could not move at all. They basically get tighter. The tighter they get the more wear they cause on the transmission line causing the ird and diff to fail.
Click to expand...

You do realise that in saying that you have destroyed our peace of mind:D
 
The Mad Hat Man said:
Wot? explain how a locked 4wd wud stop the car moving?
Click to expand...

The front and rear props rotate at different rpm due to the designed in different ratios (so it drives more like front wheel drive car), so in theory on a flat road in a straight line the front prop is rotating slightly faster than the rear, the VCU is constantly slipping at a slow rate to compensate for this. If the VCU was totally solid the wheels would fight each other, and the only way the car would move is if the rear tyres slipped or something mechanical gives way, i.e. IRD or rear diff.
 
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