You made no mention of what you might have already tried or simply looked into(if anything)? For example, have you properly checked the fluid level in the transmission? And what condition is the fluid (e.g., cherry red, dark brown, etc.). This (owner neglect) is often the root cause of many tranmission problems, as the transmission itself, without a turbo, is relatively robust and long lived with reasonable care.

Let us know what you've found, and we'll go from there....