Is it possible for an Allison transmission in a year 2001 2500HD Silverado 8.1 3/4 ton 4x4 with 65,000 miles with synthetic fluid flushes every 25,000 miles would need rebuilding? When my truck was not shifting properly I took it to a tranny shop that said it was worn out and needs to be rebuilt. I am the original owner and never abused it. Thanks in advance for your input. Pete