My guess, is you probably burned the overdrive band inside the transmission from when you
were stuck in the mud. Basically heating up the transmission fluid beyond the normal range.
So the overdrive clutch doesn't engage as crisply and now slides in. Replacing the band
requires disassembling the transmission and rebuilding it. $$$$. It will be up to you if you
want to spend the money to repair it or live with it. You can try replace the fluid and see if
that helps. It is probably a dark red to black. Have it checked out by a transmission
mechanic, they might be able to offer a solution.
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