Ok so here is the deal I have a 98 A6 with a 2.8L, which I found out that the engine is out of a 98 A4 2.8L quattro. Now the car still has the same tranny but they put the flywheel from the A4 tranny. I found out that, one the alternators are not the same, and now there are two differnt starters. So which alternator and starter do I put in to this car? If the engine is from an
A4 Quattro but the tranny is from the A6 with the A4 flywheel

 

I don't think there are any differences in the engines to affect the alternator or starter.

 

Well the part numbers are differnt on alternator. are also the starters look differnt to so I dont know. Cause something is draining the battery and I cant find it.

 

I should have been more clear. The A6 alternator and the A4 alternator will be different as the A6's will be of larger amps. But, the mounting of an A6 alternator on an A4 or A6 2.8 should not change. I could be wrong, but I don't think so.

Why are you looking at the alternator and starter as possible battery drain issues?

 

The 98 and 99 A6 2.8 engines are AHA code motors; the exact same for a 98-early 2000 A4s. There should be no difference in any of the parts you are talking about. In early 2000 they started with the ATQ code engine which could have some small differences.

And I am with Jeffla.....a drain problem has nothing to do with your starter and most likely nothing to do with your alternator. If it starts, the starter is good and if the battery light is not on and the voltage gauge is above 14, the alternator is good.

If the battery drains down overnight or something, there is something causing it to do so. Start by seeing how much amperage is being drawn while the car is off.