ZF Trans swap into a TDI?

[Tumbler510]

I was considering the feasibility of making a very efficient highway cruiser, and thought about putting a ZF 8-speed auto trans into an Audi with TDI.
I can't find any info on this anywhere, and was wondering if it would even be possible on this chassis.

[Audibot]

Are you talking about swapping in a TDI engine and a ZF 8-speed along with it?

I mean, I'm sure it can be done. The B8 in Europe came with several TDI options, including a 3.0, and the ZF 8-speed has been used in conjunction with TDI for some time (like B8.5 though). Footprint-wise, it's essentially the same size as the ZF 6-speed. But much more advanced, so on top of tweaking to get things to fit, you'd likely also need euro TDI rear diff, driveshaft (not sure if different), axles, subframes, etc, to make it all work. And TCU / coding to get everything to work.

Check threads on audi-sport.net and tdiclub.com, as TDIs are not very prevalent on Audizine.

[alhutch]

The Q5 TDI came with the ZF 8-speed auto, so the factory beat you to it.

[Tumbler510]

The Q5 TDI came with the ZF 8-speed auto, so the factory beat you to it.

In the states?
I can't find any info of the 6HP being used on a TDI in the American Market, and limited info on the Canadian market.

[alhutch]

In the states?
I can't find any info of the 6HP being used on a TDI in the American Market, and limited info on the Canadian market.

Yes, in the states. The TDI equipped A6 & A7 probably have it as well.

[Audibot]

Correct; the Q7, Q5, A8, A7, and A6 TDIs in the USA all have ZF 8-speed transmissions. And it's a great transmission. The 6HP unit was not used in the USA on any of the TDI units, except maybe the late 00s Q7 TDI (4.2 or 6.0 TDI; I forget). In Europe, the 6HP unit was used, along with the DSG and eventually the 8HP unit.

[19birel]

All 3.0TDIs in the US came with the ZF8HP including Q5,A6,A7,A8,Q7

Given the complexity of the swap and the cost involved you're probably better served to just buy an A6 3.0TDI and call it a day. We have an A7 with the supercharged gas 3.0T and it'll do 31mpg on the highway, I'd imagine an A6 or 7 with the diesel would be comfortably in the 40s.

If you really want to go for it, though, it's feasible.

[Audibot]

We have an A7 with the supercharged gas 3.0T and it'll do 31mpg on the highway, I'd imagine an A6 or 7 with the diesel would be comfortably in the 40s.

If you really want to go for it, though, it's feasible.

Speed dependent, of course, for mpgs, but fuel quality is huge in the diesels. Helps mpgs, power, smoothness, and engine noise. And tire choice is big--I lose about ~3 mpg going from the Toyo Proxes 4 Plus tires I bought the car with to Michelin Pilot Sport A/S 3+. The Michelins have far better wet and dry handling characteristics, and since I drive spiritedly, this mattered to me.

One thing I lament is the poor quality control on diesel. Stations are required to have "minimum 40 cetane" but it is rather hit or miss what you are getting--could be 40, could be 43, could be 47. No idea, unlike gasoline octane ratings.

There they are stations that carry higher rated fuel (e.g., Southern States has a 50 cetane fuel, but unavailable where I am). I believe where OP is in California would have higher quality fuel around, but one has to be careful with any that have biodiesel (I think B5 is OK; B20 might be too much). There are some good additives out there, like PowerKleen or Stanadyne, that do help a ton. There is also a few companies trying to make a "Top Tier Diesel" fuel rating. Currently an Exxon near me has the best diesel; haven't tried Shell because the ones near me say diesel but never have it. And surprisingly Royal Farms has not been terrible.

I've hit 40-42 mpg if I leave on adaptive cruise at ~75 mph and there's no one else on the road acting stupid; i.e., driving slow in the lane, meandering all over the place, etc. And 38-40 mpg going 80+ mph under similar conditions.