I was just reading this Article and the section on Viscous Limited Slip Differentials made for interesting reading:

"Viscous LSDs are less efficient than mechanical types, that is, they "lose" some power. In particular, any sustained load which overheats the silicone results in sudden permanent loss of the differential effect.They do have the virtue of failing gracefully, reverting to semi-open differential behavior. Typically a visco-differential that has covered 60,000 miles (97,000 km) or more will be functioning largely as an open differential; this is a known weakness of the original Mazda MX-5 sports car. The silicone oil is factory sealed in a separate chamber from the gear oil surrounding the rest of the differential. This is not serviceable; when the differential's behavior deteriorates, the VLSD center must be replaced."

In light of this, is it possible that many of us have a non functioning Visco drive?

Depends on the power and how you use the car. There's been several threads on this. Experiences differ with regards to longevity, but it's commonly accepted that mechanical diffs live longer as they are not dependent on the characteristics of a fluid - which may indeed change over time.

In the documentation there is a warning somewhere that the car should not be driven for prolonged times with the front wheels running at different speeds eg. when driving in snow with one wheel and the other on grippy concrete.

I personally like the viscous LSD's more because they act smoother than a mechanical diff (no sudden locking effect).

On the other hand, they're known to let the car 'wander' a bit under acceleration with the tyres slightly spinning: the LSD heats up so the diff locks so the plates turn at the same speed again so the fluid cools down again so the LSD opens up a bit again causing the LSD to heat up and... ad infinitum. This makes the car go right-left-right-left ever so slightly. If it does this, your LSD is still in good nick.

I think its a myth as the drag/loss is very minimal in comparison to modern vehicles IMO .
Just my opinion though.

I've killed two viscodrives - one through towing while the gearbox was locked (due to a broken diff) and one through wear and tear - I only found out when Motormech stripped the car after my last Ten of the Best event - the viscodrive was completely shot and giving no resistance - it explained the torque steer I was getting on the handling circuit

I have a Quaiffe in now, but it's an acquired taste - certainly not as inconspicuous as the viscodrive

I think mine might be shot. Are these avialable new and if so can anybody give me a ball park cost?

Will ask my guy at Fiat Mark and let you know

My old Eper is saying the viscodrive is still available, part # 7673708 @ £468, but my version is a few years out of date so they'll be well over £500 now if still available.

A couple of interesting quotes from the service manual:





There's an old thread here which mentions rebuilding them:

http://www.fiatcoupeclub.org/forum/ubbthreads.php?ubb=showflat&Number=1186561&page=1

http://www.baramotorsports.com/

is the company mentioned.

Thanks chaps, will get my diagnosis tomorrow. The garage are fully expecting the problem to be pothole damage to tyres or similar.

Retail is over £600 lol
Plenty still in stock in Italy .

Ouch, but pleased to see it is available as a key component of performance delivery. Cheers

Ouch - Quaiffe can be fitted for not much more and the difference in cornering performance is night and day, especially for highly-modded Coupes

agree with Nigel , the quaife makes a big difference and mine was bought and fitted for less than a viscodrive at retail price .

so how much for a quaiffe fitted to a 6 speed

Managed to get Fiat to reduce the cost to £320 today.
Give them a week and it'll be down to £200 I would imagine.

Then they will put them on the obsolete list at £50 soon no doubt where they will all dissapear abroad.

Qualifies fitted are anywhere between £650-£1100 depending on what's supplied,who's installing and if a box is supplied.

Being the first person to install one to a coupe and then several thereafter I can say without doubt its a must for anyone wanting reliability and increased handling.

If you can get them for £200ish delivered John, I'm up for one
Regards, Ross.

See what I can do
Fiat are keen to get rid of the stock and they have hundreds of these.

But they don't like one orders everything has to be 10 or more to get a discount.

Understood John, group buy then

If you do the legwork on a gb mate I will supply the price on quantities.
There keen to offload all these parts they know they won't sell so most of the time I tell them what I will pay not what they ask to be paid.

£50 sounds great in these times of financial difficulty! I would certainly take one at that price!

I like your thinking.
Will do my best.

Yeah, I think most coupe keepers would

Sub £100 quid and I'll take one, you can fit it John :-)

£100 and i will have one .... group buy me thinks

£100 and I'd be in.

I am interested too

Me too, LOL you just start to think most of the jobs that need doing are done! but then somebody pops up and reminds you of the other bits that are out of site and mind! that most likely need doing! LOL

Please stop telling me about all the intricate bits that are probably sh*gged

My car is PERFECT, PERFECT, PERFECT, if i say it enough perhaps i will start to believe it

And I will take 2 of your hands if it was possible? Maybe even 3 if the price is right. Thanks

I have around a dozen serviceable vicodrive units in stock in case anyone is looking for one - all checked before removal

Ok a quick straw poll:

Those interested in a new Fiat Coupe Viscous Coupling please add your name down on the following lists.

New Part supply only:
1) Pondman x1
2)
3)

New Part supply and fitting of: by Midland Car Services
1)
2)
3)

All prices to be confirmed once numbers of purchasers have been indicated.