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HOW TO REPLACE VCU SUPPORT BEARINGS ON A FREELANDER 1

HOW TO REPLACE VCU SUPPORT BEARINGS ON A FREELANDER 1

by Ed Evans, 31st March 2017

How to

Replacing Freelander 1’s rear drive shaft components is a realistic DIY prospect. Ed Evans explains

Freelander 1’s four wheel drive system comprises a split rear propshaft with the viscous coupling unit (VCU) mounted between the two shafts. The VCU itself has two sections connected by the internal viscous fluid. In normal drive, the front and rear of the VCU spins at roughly the same speed, with the fluid undisturbed. The VCU’s purpose is to transfer more of the drive to the rear wheels when the front wheels start spinning. It does this automatically – when a front wheel spins, the front propshaft (and the front of the VCU) rotates faster than the rear propshaft. This causes the fluid in the VCU to stiffen, thus forcing the rear half of the prop to spin at the same speed as the front half, sending more drive to the rear axles. The VCU is supported by two bearings, one at the front and one at the back, and these also give support to the front and rear halves of the propshaft which are each connected by a single bolt to the VCU’s splined input and output shafts. A rumbling, humming, whirring or grating noise from under the rear floor is not caused by the VCU, but by its support bearings, and only the bearings need be renewed to cure the noise. Of course, while the assembly is off the car to change the bearings, it’s an ideal time to replace the VCU if necessary, while it’s being split from the propshaft halves. Here, we’re concentrating on replacing noisy VCU support bearings, and we’re doing the job in the Britpart workshop with development mechanic, Steve Grant. We show one VCU support bearing being replaced – the process is identical for the other bearing. You’ll see that the dismantling process is the same as for replacing the VCU and/or the propshaft assembly. With care and patience it’s a good DIY job. 

General workshop tools: Torx spanners, drifts

TIME: 2-3 HOURS | COST: £45 PER BRG



> REMOVING THE PROPSHAFT/VCU ASSEMBLY

Before removing the assembly from under the car, it’s wise to mark the respective positions of the propshaft flanges and the IRD and rear diff flanges to help reassembly. The Tripode joint at the IRD end of the front propshaft needs to be treated with care when disconnecting and lowering the drive assembly, because it is easily damaged if over-extended or knocked. Otherwise, once the assembly is on the bench, we need to detach the two propshafts from the VCU, and then remove the support bearings from the VCU’s input and output shafts.

CONFUSING SYMPTOMS

When driving this Freelander I’d heard an occasional knock from the rear when taking up the drive. This is usually caused by one or more failed rear differential supports, especially the forward one, which allows the nose of the diff to lift when taking up the drive – the diff/prop flanges move up and hit the underbody. On this car though, I’d already replaced the rear diff mountings, so we checked for propshaft movement at the VCU end and found the knock was caused by failure of the rubber which holds the VCU bearing in its support bracket.



^ Pushing up on each propshaft close to the VCU support bearing showed free movement, caused by the rubber bearing support having broken up.



^ A more common cause of the same symptom is failure of this rear diff mounting, allowing the propshaft flange to lift and contact the underbody.

> DISMANTLING THE ASSEMBLY

After detaching the two propshafts from the respective shafts on the viscous coupling, the two support bearings should, ideally, be removed using a press, though the equipment needed for this is rarely available. Instead, the bearings can be carefully drifted off the VCU shaft, as we have done here. However, it’s important not to put any loading through the VCU, so the VCU should be held firmly on whichever side the support bearing is being removed from.



The car being worked on here is a year 2000 L-series diesel owned by Jules Evans, and used for green laning in standard form, except for BF Goodrich AT tyres.

1
STEP 1
STEP 1

> REMOVING THE PROPSHAFT / VCU ASSEMBLY: The input and output shaft of the black VCU (centre) are held by a support bearing each side, bolted to the underbody of the car.

2
STEP 2
STEP 2

Each propshaft is held by a single bolt (arrowed) passing through its U/J yoke into the centre of the VCU’s splined shaft.

3
STEP 3
STEP 3

After bending their lock tabs, the bolts (17 mm AF) holding the props to the VCU are loosened slightly while the assembly is held firm.

4
STEP 4
STEP 4

The rear section of the propshaft is unbolted from the rear diff, leaving one bolt fitted loosely for now. (Torx E11 bolts, 13 mm A/F nuts.)

5
STEP 5
STEP 5

The front prop joint is held by six bolts and nuts (size as rear) with three spreader plates. One bolt is left loosely fitted.

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