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A Freelander Viscous Coupling Unit (VCU) should be replaced approximately every 70,000 miles - otherwise you risk doing damage to the rest of the drive train (IRD, Rear differential and even gearbox - expensive repairs!) [My vcu failed at half this mileage (35k) so taking their advice would have caused damage to my Freelanders transmission, as it continued towards 70k miles. It's lucky I'm on ere and test my vcu regular.]
Why does my VCU need replacing regularly?
Your VCU is a sealed unit containing a viscous fluid. [Tell us what the fluid is, and it's correct rating if you know it.] Over time the viscous fluid becomes thick and the prop shaft no longer rotates at the required speed.
This puts tremendous strain on the drive train, and, if not replaced in a timely manner, will eventually cause damage to the rest of the drive train, such as your IRD and rear differential.
How can I tell if my VCU needs replacing? [Test it yerself.]
There is no definitive test for the VCU as it is a sealed unit, so the condition of the viscous fluid cannot be checked. [That's not strictly true. We have the One Wheel Up Test and Turnip Test. These tests give you an example of the performance of your vcu, which is a representation of the performance of the workings of the vcu inside. That would presumably include the silicon fluid, which is at the heart of how the vcu functions/operates.]
If your VCU has passed its useable life your Freelander will feel as though it is holding back on you, especially when turning corners on full lock. [For completeness they should also mention there's a certain amount of "tightness" feeling from a fully working brand new vcu. There's also a tightness feeling when you don't have a vcu fitted.]
Although a number of sites [That's us. They could at least give us a mention.] on the internet suggest different methods for checking the condition of the VCU, none of these are a reliable test. [The information ere int too reliable. Sweeping statements...]
To avoid damage to the rest of your drive train you should ensure that your VCU is replaced regularly - approximately every 70,000 miles. [Previously covered. But you could also go mondo mode by removing the vcu which is the only permanent cure to stop potential problems if a fitted vcu were to fail, and cause drive train damage.]
WARNING: If you buy a second hand viscous coupling unit (VCU) or prop shaft because your viscous coupling unit (VCU) is beyond its usable life, there is no way of telling the condition of the viscous fluid in your replacement VCU we strongly recommend that you DO NOT replace your viscous coupling unit (VCU) with a used unit. [If you buy a second hand vcu you simply test it yourself. That way you will know it's condition. In the same way you should test a reconditioned vcu, just in case you buy a faulty one from an unscrupulous seller.]
The only reliable replacement is a reconditioned unit which has had the viscous fluid replaced, or a new unit. [A reconditionned unit won't have the correct fluid inside as knowone knows the correct silicon and it's rating, other than GKN who manufacture brand new vcu's (and potentially land rover). Therefore a reconditionnned vcu will always be a greater risk, as opposed to a new one. The two cannot be compared.]
