My 4-150 has always acted a little funny when under load. It is most noticeable in the field when shifting from direct to over. It will act like it is slipping and sometimes you have to downshift to direct then back up to over to get it to grab. Other times it will hesitate and you can feel it slowly grab over a 2-3 second time span. This would lead me to believe it is the overdrive clutch pack slipping. However when taking off from a stand still on the road it will hesitate in all three speeds. I have seen three speeds fail in one or two ranges but one slipping in all three ranges seems unlikely which leads me to believe it is the engine clutch. I had time today and threw a pressure gauge on the three speed clutch circuits and it was down to about 140 PSI so I shimmed it back up to 160 PSI on the mark warm. To wet out to take it to the field and see if that made any difference though. My question, what is the best way to determine if its the three speed or the clutch slipping? Was planning on tearing it down to investigate this summer but it would be nice to be able to get it trouble shot while I still have some field work to get done with it.