I put in a new b2 piston in my 81-300SD yesterday, filled the tranny today and the car will go in reverse but will NOT go forward!!!

What did I do wrong??

Have I screwed up something?

PLEASE help with some advice.

Thanks, Don

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84-300D 256K
81-300SD 217K (Wife's)
79-300CD 212K - Project
89-Volvo 245 305K