[Cobraah1f]

I have a 2000 Impala LS with just over 100K miles. Recently started upshifting as well as downshifting pretty hard after being driven for extended periods of time. After being shutdown for awhile problem disappears only to reappear a week or two later. During one of the episodes I stopped in at a Cottoman Transmission shop to have it checked. Was told after test drive and computer dianostics that it had an internal slip code. The mechanic explained that the computer allows a certain amount of slip and once that amount is exceeded the computer shuts off the pressure control module and the hard shift is due to the full pressure shift. I was told there is likely at lot of wear and that the transmission would need to be rebuilt at a cost of $1700-2000 depending on what parts need replacing. Has any one had any experience such as this? I know anything mechanical wears out and there are fluke deffects but it seems to me the transmissions should last longer than the recommended tune up interval! Any related experiences and fixes or suggestions would be greatly apprieciated!