Purchased a '10 3.0 model about 10 months ago now with about 90k on the clock. Been a maintenance nightmare ever since, and for about the past 3,000 miles (driven just over 8,000 since purchased) the transmission has been slipping, especially during the shift from third to fourth gear- I can feel and hear a sort of clunking noise. I don't drive particularly aggressively, and I don't think the fluid has ever been changed. Would changing the fluid possibly solve this problem? Also, in the case the transmission has to be rebuilt or replaced - I have found a cheap '11 transmission with 30k pulled out of a 3.0 base model as well, would this be compatible? Or would it be cheaper simply to rebuild my existing unit?