Put the car in gear (or park), jack the offside rear wheel of the ground, put a socket on it with the longest bar you have got and lean on it. It should very slowly turn. If it turns easy the vcu is knackered and you are in front wheel drive moe, or if it doesnt move at all then it is seized and will damage your IRD. If you get under the car and put a mark on the outside case of the vcu near where thhe front propshaft goes in, and another corresponding mark on the propshaft, if when you slowly manage to turn the wheel, these marks should move apart.
thanks for the advice i will give that a go at the weekend
austen
Active Member
A very quick check (but not full proof) is to reverse on full lock, if it feels like the brakes are on, its knackered. Like iandle2 said, mark the 2 ends of the VCU and see if they move, although this is not full proof, as a VCU doesn't need to be totally seized to be knackered, its all to do with the amount of torque they transmit and different speeds.
thanks for the advice. Can you do that test going in full lock driving forward ?
Blippie
Well-Known Member
The key to the tippex test is to mark the right bits. If you just mark the two ends of the VCU, you don't get any movement anyway - you need to mark at leats one of the propshafts.
Freeman2, do a search for "tippex test" or "viscous coupling" and you wil find plenty of info on this.
Cheers
Blippie
austen
Active Member
if its very bad you will feel it going forward as well. give me a shout if you want me to replace it for you
Not to sure thats the case, Landrover themselves say a certain amount off 'windup' ie braking feeling is normal when reversing or moving forward on full lock, with the VCU coupling. But as you say the degree to which it does and still be allright, who knows.
austen
Active Member
Yes there is a small amount of resistance even with a perfect VCU, but whne you have a totally knackered one i can assure you its very noticable. Trouble is they deteriote slowly so you don't notice it, and to make things worse, a vcu doesn't have to be totally seized to wreck the IRD unit
Blimey!. When do you make a decision to change it. Can they be repaired, or is it best to go for a new one. Do they even deteriate on the spares shelves, lying there for years?. Mines is off at the moment, lying in the garage. The last time I refitted it I 'thought' it was a bit tighter when reversing, but it passed the Tippex test OK. When I held it in the vice by the prop shaft I could turn it fairly easy with a bit of effort with an 18" bar, it turned slowly and steadily. I've since bought new bearings for it too fit when I put it back on for the MOT, but it looks as though I'll have to look at this VCU again in a new light. Problems -problems.
austen
Active Member
They last about 60k miles, but i have seen cars with only 35k on them needing a new VCU. It all depends what you do with the car, if you do a lot of towing, off roading, tight manoevering or run with tyres with a lot of difference in wear it reduces the life.
No need to refit for the MOT, i've just put a car through with no prop or rear diff!
OK, playing devils advocate here, but is it worth the DIY mechanic replacing the VCU at 60k miles as a "service item"?
Obviously if you are reliant on the main stealers, it's not worth even considering unless you are a sultan of some oil nation.
As the wear in a VCU is progressive and it seems, hard to measure with any accuracy, does it therefore become a routine service item?
d.
austen
Active Member
They are straight forward to fit, although if they are seized on the splines of the prop shaft can need a bit of "persuading" to remove, just be careful not to bugger your UJ's up when you doing it. I usually replace them when i buy the car as they have usually all done 70k+
Hippo
Lord Hippo
If your markers haven't moved after a drive then either your vcu isn't slipping or it's bad luck the markers are aligned coincidently in the same place, after a drive. I suspect not slipping which is bad news. Try the One wheel Up Test. It's betterer.
Done the one wheel test yesterday, turned wheel and rear propshaft moved accordingly, front shaft didn't turn however, but that makes sense to me cause if front was turnin the jeep would be trying to move with the drive of the shaft. I think I've avoided disaster, if not shafts being dropped out cause haven't money to blow on a vcu unit,
teddywood1
Well-Known Member
AAAAAAGH he mention JEEP
I bought a viscous coupling from Beaumount 4x4 exchange basis, they have them on the self, i asked for a loose one, they do 3 types, loose, standard and tight.
The loose one is very good if you're only doing green laning etc, tight one obviously is for competition serious off roading.
So far its been working well, while its off i would also replace the prop bearings?
The loose one is very good if you're only doing green laning etc, tight one obviously is for competition serious off roading.
So far its been working well, while its off i would also replace the prop bearings?
