awdcherokee

ok i need help !! i have a 1997 jeep gc limited 5.2L AWD. it just tripped 200,000 miles and it is acting funny. When you first start it and drive it, it does wonder ful. When the tranny heats up AND it gets up to overdrive, it makes a faint grinding sound. It only does it AFTER it heats up. I took it to a tranny shop and they told me that the tranny was shot and it was $2000.00 to fix. I have a hard time believing that the tranny is bad when it only does it after heating up. They also said that the governor pressure sensor is not doing its job. Is it possible to convert the AWD to a 2-wheel drive? And can I swap trannys with any other years beside 1997? Please help! Im desperate for advice.