Have 2001 LS200 with 109K miles. Bought it used with 14K miles in 2002. Transmission shifting hard through gears [at higher than usual RPMs]. This "hard shift" was followed by Service Engine light. Took car to Econo Lube place and was told needed trans flush. Did that and car smoothed out for 10-15 miles. Now shifting hard again, but runs smooth when cold. After heating up it shifts hard again. Took back to shop and they said "need to take to transmission shop because they didn''t know what was wrong or how to fix - probably need new trans" Would appreciate some guidance. Thanks in advance.

What code was set. P1811 maybe? If so may need a pressure control solenoid