Grinding when Shifting to First Gear - 2005 VW Jetta 2.5L (5-speed manual)

Question

I have a 2005 VW Jetta 2.5L (MK5, 5-speed manual) and the clutch grinds when I shift into first if I don't depress the clutch pedal for about a second or two first. One thing to note is that before I purchased the car, the previous owner had a single-mass flywheel installed, replacing the OEM dual-mass flywheel. I believe they also replaced the clutch.

If I just press the clutch and immediately shift into first it will grind and then go into gear.

If I press the clutch for a second or two, then it shifts into first with no issues.

So from doing some research, my initial assumption is that there may be air in the clutch hydraulic system, or the pedal-to-master cylinder adjustment is incorrect.

Any other suggestions? How would I verify which is the issue?

Answer 1

What happens if you push down the clutch pedal then immediately shift into 3d or 4th gear?

Because the 3d and 4th gear synchronizers are much less likely to be worn, grinding then suggests a clutch operation problem, like air in the clutch hydraulic system, or a failed clutch slave cylinder.

Smooth gear engagement in 3d or 4th, on the other hand, suggests the problem is a worn 1st gear synchronizer, which might have developed if the previous owner regularly shifted in a forceful or impatient manner.

Answer 2

It sounds like the syncroizers for that gear may be failing. "Sycros" spin faster than the previous gear to provide a clean shift into the next gear. Performance cars and Tractor Trailer Trucks do not have syncros so instead the drivers must Rev their engine up slightly higher, to prepare the next gear.

For instance: If you're shifting into first gear from 0mph, bump your throttle to 2,000rpms and shift into gear. If you're shifting from first gear into second, repeat the above step.

This will prevent you from having to have internal parts in your transmission repaired for a while and can also give you that "racey" feel that all stick shift drivers enjoy!