I have a similar problem in my Stealth, replaced the clutch, bled it a bunch of times, and it still grinds if you shift too fast. Conclusion: syncros in the transmission were bad. For a while, changing to a thinner transmission fluid (gear oil) helped a bit but it jsut keeps getting worse...to be fair I've put 30k miles on it with the problem and it still grinds with no catastrophic failure (knock on wood...). You might want to change out the fluid and see if it helps. Hopefully it isn't the syncros because they practically require a rebuild in my experience. For my stealth they don't even sell the things, just full rebuilt units. Good luck on your sale, I hope all goes well and you can sell the wagon to a happy new owner.

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TC
Current stable:
- 2004 Mazda RALLYWANKEL
- 2007 Saturn sky redline
- 2004 Explorer...under surgery.

Past: 135i, GTI, 300E, 300SD, 300SD, Stealth