just bought this, when engine/trans cold, no problems, but after 10-15 miles, there is loud clunk as trasnmission shifts from 1 to 2 unless going grandma slow.

 

I noticed that the differential had almost no oil in it, filled it up and still the same.
drained tranny fluid, put in 4 quarts of honda fluid and dexron3 converter, still the same. Works nice when cold though.

 

the 1 to 2 is a honda /acura thing.
i drove 3 acura,s.and all 3 have that.
the dealer told me...live with it

 

You might try a transmission service with one of those machines that forces out the old fluid while pumping in the new fluid. I had this done on my '97 RL and the shudder between the 1st to 2nd shift disappeared. By the way the total fluid exchanged was close to 13 quarts!