I just purchased a 1992 integra 1.8 auto trans. Stock everything. Auto trans seems to shift fine but at freeway speeds 70-80mph rev's are at
at approx 3600-4200 and car never seems to step down revs, unless I
drop speed down. Already replaced vacuum mod. any ideas or is this normal range for this car.

 

no thats a little high, I test drove a 91 integra with an auto for my little brother and took it out on the freeway and it was running the same rpm's as my 92 rs 5 speed, it was at 3200 rpm's at 70 mph. It sounds like 4th gear might not be going in or not locking up????? Solenoid???? Valve body????? TCM (tranny control module) Have a good tranny shop look it over for you.