Reconditioned Audi A6 Gearbox

A6 diesel: 5-speed up to 2005, then 6-speed across all engine variants

Across the 1997–2018 range covered by this collection, the A6 diesel spanned three generations (C5, C6, C7), and the number of gears is the first chronological reference point to bear in mind. The 2.5 TDI engines (codes AFB, AKN, BCZ, BDG, BFC), found on the C5 generation, are fitted with a 5-speed manual gearbox. From the C6 generation onwards, with the introduction of the 2.0 TDI, 2.7 TDI and 3.0 TDI, the transmission moves consistently to 6 speeds — an internal ratio change that makes gearboxes incompatible across generations, even where the engine capacity appears similar.

Identifying the correct gearbox using the engine code

The engine code stamped on the block is the only reliable identifier, as several engines with similar capacities were fitted with gearboxes with different final ratios. The 2.7 TDI covers four codes (BPP, BSG, CANA, CGKA) spread across the C6 and C7 generations, whilst the 2.7 TDI quattro 190 hp (code CANC) is fitted with a 6-speed gearbox specific to the four-wheel-drive transmission. The 3.0 TDI (CDUC, CDYA, CDYC, CGQB) shares the same 6-speed ratio family but with ratios adapted to the higher torque output. For the 2.0 TDI (CGLC, CGLD, CGLE, DFBA) and the 1.9 TDI (AFN, AVF, AWX), a 6-speed gearbox is also fitted, but the casings and mounting points differ: confusing these two engine variants when ordering will result in a direct mechanical incompatibility.

Common symptoms and points to watch on these transmissions

On the 5-speed gearboxes of the 2.5 TDI, the 3rd and 4th gear synchromesh rings are the components most susceptible to wear, typically presenting as difficult gear changes when cold. On the 6-speed units of the C6 and C7 generations, rear casing seal leaks and output bearing wear are the most commonly reported failure points. In all cases, identification by engine code remains essential before placing any order: the vehicle's year alone is not sufficient, particularly during the transition years between generations.