How easy is it to do the VCU on a P38?

kooky_guy · Apr 20, 2010

Pretty sure my viscous coupling has seized. It does turn but at nowhere near the speed it should (60ft/lbs on a wheelnut).

It looks to be a straightforward job in Rave. Is it? Any hidden pitfalls? Is the silicon sealant anything special? Anyone know of a photo guide to doing it?

And finally where's the cheapest place to get a new VCU?

Yet another unexpected job!

Cheers

Guy

the hooded claw · Apr 20, 2010

As you know I have the very same problem ............Fitting one is easy..ish!! but @£300 its abit ..errrr Expensive

I've just dropped the front prop & am running as RWD only ...I'll get it done ..EVENTUALLY but in the mean time (& if yer NOT offroadin) .. just drop the prop ............

Datatek · Apr 21, 2010

kooky_guy said:
Pretty sure my viscous coupling has seized. It does turn but at nowhere near the speed it should (60ft/lbs on a wheelnut).

It looks to be a straightforward job in Rave. Is it? Any hidden pitfalls? Is the silicon sealant anything special? Anyone know of a photo guide to doing it?

And finally where's the cheapest place to get a new VCU?

Yet another unexpected job!

Cheers

Guy

If it turns with 60 foot pounds it sounds perfectly good to me. A seized VCU is impossible to turn.

kooky_guy · Apr 21, 2010

Datatek said:
If it turns with 60 foot pounds it sounds perfectly good to me. A seized VCU is impossible to turn.

I can't turn it by hand on the wheel (but perhaps I'm just weedy!) but it did turn slowly with a torque wrench on it.

A test I was given was to jack up one front wheel, handbrake on and in neutral. Put a socket on a wheel nut and turn it at 60ft/lbs with a torque wrench. The wheel should rotate 90 degrees in a minute.

Mine rotated about 20 degrees in a minute.

For some reason it turned more easily one way than the other, but it's quite hard to rotate it that way because the wheel nut kept undoing!

Since I replaced the front propshaft (front UJ was completely knackered), it's felt a bit harsh at the front which I have been imagining might be transmission wind up. Or I could just be imagining it!

With so much else needing doing, I don't really want to add a front diff to the list, but it's not really showing any other signs of a seized VCU - doesn't squeal on full lock, it will creep backwards on full lock and the tyres seem ok. But it does feel rather sluggish and clunky.

Ashcroft seem to think that at my mileage the whole transfer box should be overhauled, but that's rather out of the question at the moment.

Perhaps I'll wait until it's serviced and get West 4x4 to test it.

Decisions, decisions.

Guy

wammers · Apr 21, 2010

kooky_guy said:
Pretty sure my viscous coupling has seized. It does turn but at nowhere near the speed it should (60ft/lbs on a wheelnut).

It looks to be a straightforward job in Rave. Is it? Any hidden pitfalls? Is the silicon sealant anything special? Anyone know of a photo guide to doing it?

And finally where's the cheapest place to get a new VCU?

Yet another unexpected job!

Cheers

Guy

Think someone has told you wrong. Viscous should turn at 27lb feet with a socket on the front output flange nut. So seeing as how we have a 3.54 to 1 diff in the way when we turn the wheel that would multiply the torque required to around 90lb feet on the halfshaft retaining nut. As the torque value for the wheel nuts is 80lb feet that would explain why they come undone going the other way. If it turns at all it's not seized. If it takes more than 90lb feet it may be on it's way out.

kooky_guy · Apr 21, 2010

wammers said:
Think someone has told you wrong. Viscous should turn at 27lb feet with a socket on the front output flange nut. So seeing as how we have a 3.54 to 1 diff in the way when we turn the wheel that would multiply the torque required to around 90lb feet on the halfshaft retaining nut. As the torque value for the wheel nuts is 80lb feet that would explain why they come undone going the other way. If it turns at all it's not seized. If it takes more than 90lb feet it may be on it's way out.

Wahay! That sounds like better news. Thanks Wammers.

The advice on Ashcroft transmissions website is something similar to that - I think they quote 30lb feet on the output shaft, but they also go on to say that the same test can be done on the wheel nut (without giving a revised torque figure). Now even I thought that must be wrong, but I thought 60 on the wheel nut sounded reasonable, which is what someone on another forum quoted me.

I'll stop worrying about it for the time being then and worry about my heater o rings instead...

Thanks everyone.

Guy

ex darksider · Apr 21, 2010

wish i could help you as you've been so helpfull to me but viscous coupling bit over my head aint that a **** load of clutch plates,can you afford and do ashcroft even sell that seprate i've heard they are the muttz

wammers · Apr 21, 2010

ex darksider said:
wish i could help you as you've been so helpfull to me but viscous coupling bit over my head aint that a **** load of clutch plates,can you afford and do ashcroft even sell that seprate i've heard they are the muttz

**** load of clutch plates yes, but it is a sealed unit that just slips onto the centre diff on splines. About an hour to change on a ramp. Pretty simple and straight forward. On your back a ball ache.

Stufer · Apr 21, 2010

kooky_guy said:
Wahay! That sounds like better news. Thanks Wammers.

I'll stop worrying about it for the time being then and worry about my heater o rings instead...

Thanks everyone.

Guy

Guy,I did my o-rings a couple of weeks ago, got a shed load of pictures but not had time to upload them yet, maybe tomorrow, going to try and label them in Powerpoint first. Job not as difficult as I expected and saved me £650 quid quoted by the garage....

kooky_guy · Apr 21, 2010

Stufer said:
Guy,I did my o-rings a couple of weeks ago, got a shed load of pictures but not had time to upload them yet, maybe tomorrow, going to try and label them in Powerpoint first. Job not as difficult as I expected and saved me £650 quid quoted by the garage....

That'd be good. I've just got to find a weekend with enough hours in it to allow me to start it!

Theroadlesstravelled · Feb 6, 2013

wammers said:
**** load of clutch plates yes, but it is a sealed unit that just slips onto the centre diff on splines. About an hour to change on a ramp. Pretty simple and straight forward. On your back a ball ache.

Hi Wammers,
do you know of any links on how to do the job or any information you can give on the best way to to change the unit ? any info would be appreciated

wammers · Feb 6, 2013

Theroadlesstravelled said:
Hi Wammers,
do you know of any links on how to do the job or any information you can give on the best way to to change the unit ? any info would be appreciated

If you look at the overhaul section of RAVE >Transfer box. It will give you an idea of what is involved. Pretty simple job all in all.

Theroadlesstravelled · Feb 7, 2013

Thanks for that, job for tomorrow and hope all goes well have the use of a lift for the day

How easy is it to do the VCU on a P38?

kooky_guy

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the hooded claw

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Datatek

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kooky_guy

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wammers

No longer with us, RIP

kooky_guy

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ex darksider

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wammers

No longer with us, RIP

Stufer

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kooky_guy

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Theroadlesstravelled

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wammers

No longer with us, RIP

Theroadlesstravelled

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