Hi,
I've owned an auto A4 3.0 TDI and two manuals (A4 2.5 TDI & A4 1.9 TDI) all with Quattro.
Your question is not an easy one to answer! I agree that auto boxes suite the torque and power delivery characteristics of diesels, but how much this applies really depends on the power output of the engine!
Out of the four cylinder TDIs available in the A4 B7 range, I'd only consider getting an auto on the 2.0 TDI 170bhp. In my humble opinion, the 140bhp & lower engines are too under-powered for the auto box, especially when fully laden!
Both the 2.7 and 3.0 have plenty of umph to drive the auto box, no question there. As their lazy V6 configuration isn't as punchy low-down as their 4 cylinder cousins, the auto box suits them particularly well.
Ultimately, I think it comes down to how you drive most of the time:
If you spend a lot of time in traffic, you drive sedately and are generally a laid back driver, then auto is undoubtedly the best choice. It's a phenomenal driver aide.
If you regularly drive enthusiastically and enjoy taking your car by the scruff of the neck - you need manual, no doubt.
Having driven all my TDI's across the Snake Pass (the mountain road that links Manchester to Sheffield across the Pennines) I can say that there's nothing worse than being at the mercy of an auto gearbox when you want to drive progressively through tight corners and bends!
Even in sport mode, an auto box often leaves you in the wrong rev range or gear to get the power down when you
really need it! You cannot beat having control of the clutch, revs and gear if you are an enthusiastic driver.
Tiptronic is a real advancement over standard auto, but I think it's most effective in naturally aspirated large capacity petrol engines (where turbo lag isn't a factor). My personal opinion is that Tiptronic is wasted in most diesels.
Admittedly it is great for changing down a gear when going round a long sweeping bend, but isn't great in tight bends).
In retrospect, I'm pleased I had auto in my 3.0 TDI because I drive sedately most of the time. Occasionally the auto box frustrated me - I wanted to take advantage of that awesome 3.0 lump + Quattro (the auto box never really lets you do that!)
I am enjoying the manual box in my 1.9 TDI Quattro at the moment, it really suits the engine. When I eventually upgrade to a 2.7 TDI, I'm pretty sure I'll be going for auto again - it's all about the smoooooth ride
Hope that helps!
Al.
PS: The downside when buying a manual 3.0 TDI is: they have monstrous torque figures and they are more likely to have been abused (as opposed to the auto which is offered some protection by the torque-converter's max torque limit).
