Drivetrain shudder on throttle lift after kickdown
 

Hi all - I have a 2005 Continental with about 46k miles. I've been using it as a daily driver all summer. I've had a couple of weird things happen on the highway over the last few weeks.

After accelerating quickly to pass, and generally having the trans kick down to do so, if I abruptly lift off the throttle there's sometimes a pronounced shudder through what seems to be the mid to back of car. First time it happened the car pout itself into trans fault mode and stayed in 3rd gear. Situation cleared right away on restart. VCDS logged this:

Address 02: Auto Trans Labels: 09E-927-156.lbl
Part No SW: 09E 927 760 G HW: GS1 904 1
Component: AG6 09E 6.0L W12TT 1905
Coding: 0000101
Shop #: WSC 00083 000 00000
VCID: 3431E274022A1E1B5BB-513C

1 Fault Found:
17119 - Gear 5
P0735 - 000 - Incorrect Ratio - Intermittent
Freeze Frame:
Fault Status: 00100000
Fault Priority: 0
Fault Frequency: 1
Reset counter: 32
Mileage: 73522 km
Time Indication: 0

Freeze Frame:
RPM: 3424 /min
RPM: 3232 /min
RPM: 3424 /min
(no units): 37.0
(no units): 183.0
Temperature: 80.0°C
T.B. Angle: 80.8°

Second time was just the other day. Perhaps an even more pronounced shudder but car did not go into trans fault mode. I haven't done another VCDS scan on it yet though.

Seems to just happen after WOT (or close), trans kickdown, and letting off the throttle (because by that time I'm going far faster than I need to be!). Anyone have similar experiences?

That suggests to me that for whatever reason there was slippage inside the transmission when the control computer wasn't expecting it.

That can occur because of inadequate oil pressure either as a result of insufficient oil, too thin oil, mechanical wear in the drum, mechanical wear in the valve block, and probably a variety of other reasons.

Starting with the simple things: Do you know when the transmission fluid and filter was last changed?

I'm aware that a filter change doesn't occur on the official VW service schedule, but I struggle to understand why anyone would specify a fluid change without a commensurate filter change. Even ZF seem now to accept that their "sealed for life" gearboxes aren't, indeed they sell fluid/filter/magnet/bolt service kits. The part number for yours is 1068.298.054 which in Europe costs $250.

Agree with DG! Also to eliminate any further uncertainties would suggest the use of ZF 6 Lifeguard fluid. Also each container must be shaken to get the additives equally distributed [the fine print on each bottle].

Regrettably the incorrect ratio error on the ZF6 HP26A61 is a known problem. There is an Inner bushing that prematurely fails as well, this requires a transmission out repair. Hopefully not in this case.

Some have had success with fluid and filter change. There is also a possibility the bridge seal above the valve body is leaking, as well as the four clutch seals, serviceable items, requires dropping the valve body only.

Hopefully when this fault happened there wasn't a hooting sound. When the problem gets worse there is that sound of slippage.

Some may suggest resetting adaptations, not possible on 04 and 05, with RT vcds. Possibly ZF can force a reset, after a fluid and filter service.

Since this problem will continue, best course of action is to find a certified ZF transmission specialist. The dealer will only recommend replacement of the transmission.

BMW, Jaguar, Land Rover and VAG group including Bentley, with the above transmission are susceptible to this problem and a few other problems.

No clue on when (if ever) it was changed. I've owned the car for about 2 and a half years. No perceptible trans issues except for this.

Can the VCDS tell me if the trans fluid is low?