Viscous Coupling working?

[Rayngie]

Hello, How can I check if my Classic's Viscous Coupling is working?, preferably on my driveway as to opposed to mud bogs ( not many in cremorne )Cheers,

[Scouse]

I'm not sure that this is the best way, but it will work:

One a level/smooth surface, lift up one wheel using a trolley jack (making sure the jack is lined up with the car).

Try to move the car (drive away), just make sure you do this very slowly.
If the car wants to move, then your viscous is working. If the lifted wheel just spins happily away & the car doesn't move, then the viscous isn't working.

[disconut]

I'm not sure that this is the best way, but it will work:

One a level/smooth surface, lift up one wheel using a trolley jack (making sure the jack is lined up with the car).

Try to move the car (drive away), just make sure you do this very slowly.
If the car wants to move, then your viscous is working. If the lifted wheel just spins happily away & the car doesn't move, then the viscous isn't working.

The efficiency of the coupling is directly proportional to the size of the hole in the side of the house! :D:D

Trev.

[4bee]

Just what are the legalities of proceeding on the Queen's Highway with 3 x normal road wheels & 1 x Trolley Jack, directional control & speed notwithstanding.:D

;)

[BigJon]

I believe the common failure with the viscous couplings is seizing, rather than not locking. Jack one wheel up in the aforementioned manner and try to turn the lifted wheel. You should be able to turn it with some resistance. If you can't turn it, the coupling is seized.

[moorey]

I believe the common failure with the viscous couplings is seizing, rather than not locking. Jack one wheel up in the aforementioned manner and try to turn the lifted wheel. You should be able to turn it with some resistance. If you can't turn it, the coupling is seized.
Dumbass Q, but does this apply to defenders? Mine is pretty ****e offroad with an unweighted wheel. When I jack it up to change tyres, the rear locks (assuming we are only talking rears).... or my handbrake may have been on:rolleyes: ....
Assuming it is siezed, is it an easy home fix (for a newby) or a major job?

[BigJon]

Defenders have a centre diff lock, rather than a viscous coupling. Diff lock is engaged by pushing the transfer lever (short one) over to the left (passenger) side of the vehicle. Must only be used in low traction conditions.

[101RRS]

Lift a rear wheel of the ground and testing is the standard way of testing a Freelander VC - however people who haven't actually done it say you can move the wheel by hand - not so. I need to use a 2' breaker bar on the hub nut and apply steady pressure and the wheel will slowly turn - if you try and jerk it it will not move. There is no way the wheel can be turned by hand.

I assume a RR is similar.

I have contacted the stealer and GKN (the makers) about a more technical way of testing, such as the torque setting range for a serviceable VC to move but it seems there are none - well none that they are releasing.

I don't understand why these cannot be made a serviceable item and be able to change the fluid at regular intervals. When I have time I am going to pull my seized one apart to check this very point out.

Gazzz

[moorey]

Defenders have a centre diff lock, rather than a viscous coupling. Diff lock is engaged by pushing the transfer lever (short one) over to the left (passenger) side of the vehicle. Must only be used in low traction conditions.
Cool, I get the centre diff thing, I just wasn't sure if the VC was sort of like LSD on the rear....like I said, I'm a bit of a dumb ass:rolleyes:
Thanks BigJohn

[Rayngie]

Thanks for this, will jack it up and try, only trying to find out as I was trying to get up a sand dune on the weekend, my mates in a defender and very heavy patrol cruised up it and i could get close but no cigar ( tyre pressure at 18psi ), bent my nose right out of joint....could'nt think of anything else that could have been wrong...than again, maybe it was just me...

[dungarover]

The Viscous coupling box generally will seize when they start to play up.

My 93 Rangie I found that the VC box wouldn't work correctly prior to the rear diff lock being installed (ARB air locker At the time). It was much worse when I engaged the locker, the drive would slip to the front and the rear would spin slightly or not at all.

So I replaced it with a LT230 with a CDL. There's no comprimise, locked when and how you want it and cheaper to replace (although the VC hubs have dropped in price, especially if you import from the UK :) ).

Anyway, good luck with it.

Trav

[Pedro_The_Swift]

The efficiency of the coupling is directly proportional to the size of the hole in the side of the house! :D:D

Trev.

ROLMAO!:lol:

[adm333]

It probably doesn't help much, but the following is an excerpt from the workshop manual for Viscous Unit - Rolling resistance bench test


NOTE: Testing should be carried out in an
ambient of 20 °C.
9. Secure the output shaft in a vice fitted with soft
jaws, gripping the shaft on the drive flange
splines.
10. With the viscous unit still installed in the front
output housing place the assembly on the rear
output shaft spline.
11. Apply a clockwise torque of 27 Nm to output
flange nut. If no resistance to turn is felt, unit
requires replacing.
12. If resistance to turn is felt, apply a clockwise
torque of 20Nm,to output flange nut for 1
minute, this should result in a rotation of
approximately 25° - 30°. If no rotation or a
greater force is required, unit requires replacing.

[Rayngie]

Right, Finally got around to jacking up the rangie, wheel spun very nicely, car did'nt want to move at all,Ergo..dos'nt go.., any advice on the best solution?, get a 2nd hand, new, replacement?, cheapest solution is the best for me..

[PhilipA]

Er, the advice of the Freelander guy only applies to Freelanders, as they are front wheel drive with a viscous to the rear wheels.
So you must jack up ONE FRONT wheel as the Range Rover is rear wheel drive ie there is a direct connection from the transfer case to the rear driveshaft and the viscous coupling is between the transfer case and the front driveshaft.
Get a large screwdriver and try to turn the front driveshaft with the screwdriver jammed in the UJ. It should turn VEEEERY slowly with a lot of effort. If you have done this and the screwdriver turns easily then it is stuffed , but I doubt you have done this. 99% of the time it is seized and you cannot turn the front shaft.

Regard s Philip A

[Rayngie]

does lifting a front or back wheel make a difference?I lifted a back wheel and it spun freely, but hav'nt done a front one yet..

[BigJon]

Our service manual for the viscous transfer case says to remove EITHER the front OR rear propshaft and then try to drive the vehicle. The vehicle should drive, excessive engine speed indicates a failing viscous unit. The book doesn't say how much engine speed is excessive, nor does it mention siezed couplings.

[PhilipA]

YES it matters.
If you had the transmission in neutral and the handbrake off the back wheel will turn easily. If you put the handbrake on the back wheel wouldn't turn, and if you put it in gear/park the back wheel wouldn't turn.

As I stated the viscous works only on the front driveshaft.
Regards Philip A

[PhilipA]

PS you have to have the tranmission in neutral when doing this.

The driving thing without a driveshaft will work as the viscous allows only a small difference in revs between the two driveshafts, but do not go too far as it is pretty hard on the Viscous. I have never tried this but I would remove the rear shaft as that means all the drive will be through the viscous, and you will soon see if it drives. I would expect a lot of slip at first but then it to tighten up as the viscous fluid heats up until it is like a solid coupling within a couple of seconds.
Regard sPhilip A

[DeeJay]

Another tactic is to do about 3 circles in 4wd on bitumen and then jack up a corner. The lifted wheel should turn with the pent up friction.:huh:
I did this b4 buying our classic & it works !!

[101RRS]

There is a lot of good advice being given but just remember when the viscous coupling fails it usually locks not loosens up so so driving around in circles and jacking up or removing drive shafts and driving around may not actually show the the VC has failed.

Cheers

Gazzz