I have Oliver 880.   It seems like it is catching on something when going up hill in 1st, 2nd,  5th and  low reverse.   Last year I put in low range input shaft bushing and some bearings on top.    Have not had a load on it , but have done  a little bush hoging around barns,   seems to catch going up hill.   Did the same before putting bushing in it.   Has helical gear transmission and power booster.   power booster works fine.