la mia penso di poter dire che è in ottime condizioni (sono fortunato?):
si sente lievissimo strisciamento della ruota post. interna solo nelle curve strettissime (tutto sterzo) solo a freddo, a caldo quasi nulla; per il resto attacca a dovere quando serve: la classica prova "fango in faccia" viene superata brillantemente!
da:
www.syncro.org/VCTest.html
"Test for Proper Function of the VC by "Dr. Rainer Woitok"
W's original (German) repair manual doesn't say much about how to test the viscous coupling. They only recommend placing the rear wheels in a break testing stand. If you then switch to the G-gear (creeping gear), the front wheels should move the van out of the test stand as soon as the engine is revving slightly above idle. If the front wheels fail to do so the viscous coupling is to be replaced, VW says. VW adds another tiny sentence to this, saying that only when the engine is revving at idle and with the G-gear switched in, the viscous coupling is able to absorb all the torque to the front wheels and keep them from moving.
To me this last and rather ill formulated (in the German manual) sentence is the key to testing the viscous coupling. For in most cases we are not dealing with viscous couplings doing less than their share, but rather with hard going viscous couplings which don't have a problem at all in moving the van out of the test stand with the engine just idling. [i.e., prematurely engaging VCs -ed.]
Thus the really important thing here is not the van successfully leaving the test stand. On the contrary, the important thing here is the van not moving and staying put in the test stand with the G-gear switched in and the engine just idling. If your Syncro doesn't pass this test your viscous coupling is probably worn out and ready for a replacement. Or put the other way round: as long as your van's viscous coupling is working properly you will not notice your van has got one. [Except, perhaps, when making tight turns in a parking lot. Some binding and chirping is ok when you make very tight turns. It is the temperature-relarted, stiffer and more easily triggered binding that is symptomatic of a problem needing immediate attention. -ed.]
How to Replicate the VW Test
Using a heavy floor jack with wheels, put a block of wood on the jack and raise the rear of the van using the skid plate. Be careful, you can bend it. The wood block, if long enough, distributes the weight across enough of the skid plate to minimize that risk. Lift both back wheels off the ground 6" or so on a smooth level parking lot, with the jack's wheels parallel to the Syncro's. The rear of the van will be moving on the jack wheels, so you need to make sure there are no obstructions that could catch the jack wheels and cause the van to fall off the jack.
Now, put a 1x1 piece of wood in front of each front tire, 2x4 may work too. You need to block the front wheels like this to be able to test whether the VC is capable of absorbing the spinning of the rear wheels without locking up and causing the front wheels to engage and climb over the wood. If you can get the rear wheels to turn/spin in the air with the clutch fully disengaged, and without the van climbing over the wood blocking the front wheels (can't be too high...1-2"), then the VC is definitely good, or the fluid is not cooked. The van should climb over the blocks as soon as you increase the engine RPMs.
It may take several tries to get the van to do this. The VC is very sensitive, and it will want to engage as you let the clutch out. Some advise using the hand brake to help slow the spin of the rear wheels ... or to start them spinning slowly at first. It is really neat when you get it to work. Suddenly, the VC is working before your eyes in a very graphic way!
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Warning! You could conceivably get killed or kill someone performing this test. If you die doing this, don't get mad at me!
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A test to see if the VC is engaging is to take your syncro out into some fresh snow or mud and induce wheel spin. If you get none up front, but the rears are spinning, you have a problem...which could be blown VC seals or perhaps a bad front differential. This test, however, does not help you diagnose a VC that is in the process of self-destructing, or is putting undue strain on the rest of the drive train, because it is engaging when it should not."
e ancora, dal sito di Westfucka:
"se hai a disposizione un campo (terra o neve) in leggera salita, entra piano puntando il muso in alto.
Prova delle partenze da fermo, con l'anteriore sterzato verso DX (la ruota Sx deve spuntare dal passaruota), dosando il gas per far slittare progressivamente le ruote dietro: Tenendo la testa fuori dal finestrino, se becchi fango in faccia dalla ruota anteriore SX, sorridi e prendilo sui denti: la tua visco funziona"[/i]
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