Probably no big deal except for the wasted gas from running the higher RPMs. There were software upgrades for the early model 722.6 trannys that resolved the clunk on downshift. If your car has not had the uprgraded controller installed, that may be your problem. My car has the old control unit in it and clunks on downshift too, but has been doing so for 129,000 miles and no problems otherwise.

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Ali Al-Chalabi

2001 CLK55
1999 Dodge Ram 2500 Cummins Diesel
2002 Harley-Davidson Fatboy
Merlin Extralight w/ Campy Record