Gear Shifting Problems: Troubleshooting Guide

Hello everyone!
I drive a 1996 A4 with an AHU TDI engine.
It now has 220,000 kilometers on the odometer.
'For the past few days, it has been making a disturbing jerking sound whenever it's started. This jerking becomes more pronounced the more weight is in the car.'
The clutch and transmission have only 20,000 km on them, so it's probably not related to those components. I'm at a loss for what to do now.
Can someone perhaps tell me what the average lifespan of a high-performance engine is?
Best regards,
Chris

Hi Chris,

If the jerking occurs while the clutch is being engaged and starting to grip, it could be due to contaminated friction surfaces, possibly caused by oil leaking from a crankshaft seal or similar.

If the jerking occurs only after releasing the clutch, please describe the situation in more detail: engine speed, how much gas you're giving it, is the engine cold or warm, etc.

Hello Chris,

There could be both electrical and mechanical causes for your problem.
Electric:
- The engine control unit (ECU) is not receiving a signal from the speed sensor on the transmission.
(Symptom: Cruise control is not working; no speed is displayed in the relevant measurement blocks of the engine control unit; there may be an error code stored in the diagnostic memory.)
As a result, the engine control unit's anti-kickback function no longer works.
Mechanically:
- What Ulf has already described.
- faulty engine mounts
- faulty drive shaft joints.

Best regards, Rainer.

Hello.
Subject: Clutch Jerking.
Because the error only occurs sporadically, troubleshooting is proving difficult.
'This issue occurs only when starting the engine with little or no throttle. As mentioned, the more the vehicle is loaded, the more pronounced the jerking becomes. When starting with approximately 1500 RPM, the jerking disappears. I've received advice to check the fuel injectors, but I'm hesitant to remove them myself, considering the engine has quite a few miles on it. I can't imagine the brake pads being contaminated with oil, as the gearbox seems relatively dry.'

Hello!
'Two days ago, I experienced exactly the same symptoms in my ALH engine. The engine was very hot, the car was fully loaded, and when starting, there was a jerk at the end of the clutch engagement. However, this only occurred in the first and second gears. Highway driving and shifting into higher gears were not a problem, so I don't think it's the clutch. The next morning, with a cold engine and an empty car, the problem was gone.'
'Since I had filled the tank at a French supermarket gas station, and the engine's rough running seemed similar to the knocking/pinging sound I've heard in gasoline engines, I then refilled about two-thirds of the tank with premium gasoline. Since then, I haven't experienced the problem again, although I haven't driven it much and haven't fully charged the battery.'
Has anyone else seen such differences in diesel fuel before, or should I prepare myself for the fact that this problem will continue to occur?
Thank you for any advice.

Hello!
I'm writing again because the jerking after shifting into first and second gear is still noticeable. It only occurs when the engine is fully warm and when accelerating quickly, but it's not always reproducible. However, it happens more frequently under heavy load.
I have the impression that the engine runs a bit rougher across the entire RPM range, but the power is definitely there. The transmission seems fine, so I'm ruling out a slipping clutch. The cruise control is working as it should.
Could there be such significant differences in diesel fuel that it manifests in a similar way? As I said, sometimes the jerking feels almost like the knocking of a gasoline engine running on bad fuel... Perhaps it's not winter-grade diesel?
Thank you for every tip.
Martin.