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Visous coupling failure symptoms


Snagger

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I have a late RRC with the Borg Warner unit. I am wondering if the viscous unit has partially seized and would appreciate your opinions, please.

I am unable to turn a lifted wheel by hand, but a local LR specialist checked the unit by twisting the prop shafts in opposite directions with levers and pronounced it fit.

However, I get scrubbed outboard tyre tread edges, occasional slight squealing from the tyres at full lock and vibration from the front drive line at 60-70mph (not a prop shaft fault).

The suspension bushes, UJs, CV joints, wheel bearings, brake discs and tyres have all been replaced, as has the entire left swivel. The bearings of the right swivel have been inspected.

I seem to recall reading someone having similar issues on a P38, which also uses the same viscous unit, and they had gone through a similar replacement list as I have, only accidentally curing the vibration when the viscous unit was found to be faulty.

Can anyone confirm or fault the diagnosis before I shell out £00 on a new viscous unit, please?

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I have a late RRC with the Borg Warner unit. I am wondering if the viscous unit has partially seized and would appreciate your opinions, please.

I am unable to turn a lifted wheel by hand, but a local LR specialist checked the unit by twisting the prop shafts in opposite directions with levers and pronounced it fit.

However, I get scrubbed outboard tyre tread edges, occasional slight squealing from the tyres at full lock and vibration from the front drive line at 60-70mph (not a prop shaft fault).

The suspension bushes, UJs, CV joints, wheel bearings, brake discs and tyres have all been replaced, as has the entire left swivel. The bearings of the right swivel have been inspected.

I seem to recall reading someone having similar issues on a P38, which also uses the same viscous unit, and they had gone through a similar replacement list as I have, only accidentally curing the vibration when the viscous unit was found to be faulty.

Can anyone confirm or fault the diagnosis before I shell out £00 on a new viscous unit, please?

Sorry to be the bearer of bad news but I have had the same symptoms on my '93 Classic a few years back and it was the VC, I ordered one from Paddock's in the UK, sent to Perth Australia, delivered in 6 days cost including freight was a little over 60% of the price from my local supplier.

EDIT: I was advised to replaced the shaft at the same time.

Edited by Bille
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If it's an expensive thing you may be able to swap it for an LT230, they're cheap and plentiful.

Very cheap - I have a reconditioned one in my Sankey, but it's almost certainly a 1.4:1, being ex-MoD. Besides, this is a really nice soft-dash, and I'm trying to keep it as original as possible (sympathetic mods only, like seat heating and aircon, using Genuine/OEM parts).

Thank you both for the replies. I'll check the Paddock price, Bille - Ashcroft want £275+VAT and my local supplier wants over £300 for a Britpart one (probably OEM, though I'm not sure).

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If the mechanic has passed it fit, what makes you think he is wrong?

A simple test:

1. Chock the rear wheels.

2. Main box in neutral, handbrake off.

3. Jack up one front wheel.

4. Grab the wheel at 3 and 9 o'clock and try and rotate the wheel.

Unless you are Superman, you should find it very hard to turn the wheel, but it should turn with a constant resistance. If it turns freely, or does not turn at all, then the VC is goosed.

Good luck!

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Regardless of what your garage man say's, if you cannot turn a lifted front wheel (transfer box in neutral & handbrake on) then the VCU has seized. The following test, carried out within days of an Ashcroft's recon unit being fitted to a RRC, may be of help to owner's with the same query/concerns: Fit a 27mm socket onto a torque wrench with about a 20 inch long handle, set the wrench for 30ft/lbs & place the socket on a wheelnut that is at the 3'o clock position (driver's side wheel). If you then apply GENTLE pressure clockwise (tightening) you should be able to turn the wheel without 'breaking' the wrench.

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As quoted on the VC section of Ashcrofts website:

A common problem with the Range Rover BW transfer case is a "seized viscous coupling". This can easily be identified by the effect it has on cornering, the tyres will "chirp" or "scrub", as the vehicle is effectively permanently in diff lock. As a confirming check, put transfer case in "neutral", handbrake on, jack up one front wheel and try to turn it, it should turn slowly with resistance, if locked solid the viscous coupling is seized, and will need changing before any damage to the diffs or CV joints occur.

I've used this method to check VCs on a few RRs and it is the test that had has always worked.

Note they say transfer case in neutral and handbrake on....

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