Trundler wrote:andysimpson wrote: I do an 2003 A4 quattro which the owner put 2 cheapo tyres on the front, i pointed out the error to him but he knows better than me and audi, that was about a year ago. It came in recently for an mot and he said it has funny vibrations.
Just as a point to clarify... Audi's quattro system is nothing like the VW 4Motion Haldex clutch system (used in the TT, despite quattro badges) or the Syncro system. It has three proper diffs and suffers none of the tyre size sensitivities of the Syncro models. In complete contrast to the Syncro, the quattro transmission is virtually bullet-proof, even after years of flinging a ton of car off the line with no wheelspin!
PS - another badge-engineering anomaly is that a Passat 4Motion is actually a quattro!
I an very familar with what type of 4wd is used on every vw/audi its all i work on.
I have another 2002 a4 quattro in work now with a broken propshaft michelins on the front wanlis on the back. Read the owner manuals of any quattro they ALL state tyres must be same make/size/tread pattern or transmission damage is possible. Prop 799.48 + fitting + 2 tyres +vat.
I agree the torsen (quattro system) is the strongest of them all but its along way of being bullet proof (2 in work in last 2 months). I think it was regarded as bullet proof up untill about 10 years ago, since then they have engines with lots of low down torque rather than the old 5 cylinders which had little low down torque, combine this with tyres mis matched and something will eventually break. It does have bad points main one being transmisson shunt which gets very noticebale with diesel or high power petrols, this does not apply to automatics.
The haldex system is by far the best, does not have the nasty shunting of the torsen and has better control of where the power goes. Down side to this system is it can be heard adjusting front too rear bias if you listen hard enough.
The viscous coupling is crude compared to others but does a similar job to the haldex its just not very forgiving about tyres.