Kevin Bacon 5 Posted February 17, 2008 I did a chain replacement this weekend and Funkster, you were right, it is gearing related. Because the oil pump and cam drive wheels are different sizes and because of the sequential injection and individual knock (which must have accurate TDC triggers), VW had to make sure the cams are at true TDC once every 4 crank turns. They did it with gearing and it only happens if the 0 or 180 markers are adhered to. The reason the factory 0 marker is recommended is because you can see that marker with the gearbox in situ. You can't see it if you use the 180 marker, or if indeed you are 90 deg out etc. If the oil pump and crank drives were the same size and teeth, none of this would matter! It's just a quirk of the VR6. If the int shaft is not in the right place, the cams won't be in the right place and therefore the sequential timing and individual knock will be way off. The reason most people don't notice their cams being half a tooth out is because the ECU adapts. The injector TDC signal it's receiving will be wrong, but it will adjust. To get a VR's maximum performance and efficiency, the int shaft must be at 0 or 180 ;-) Quote Share this post Link to post Share on other sites