3500 is way high for a trans rebuild especially considering its most likely just the b3 servo that needs to be replaced. Get a used one for a couple hundred bucks and put it in (mechanic should be able to do this in 5 hours easily). Not worth the money IMO.

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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