What do you guys think?

ok guys , well I know this will seem inconsistant but! I just took it out and this time I tried to make it happen. Well I succeded. Here is what the situation was. I ran it up to about 70 or so (wrong speedo gears) and was still given' it gas when sure enough it happened. OK here are the specifics.
It came on gradually. and got progessively more drag. I let off the gas for a sec to se if it would change and it just slowed the car til it gradually went away just as it came on. So the next thing I tried was to drop it in to second and bring the RPMs up to the same area attempting to get the same reaction in 2nd. Didnt happen though. So it is only in 3rd around 70 mph at 4500 RPMs or there about. I havent shifted this thing any higher than 5200 since I put it back together, so I know the Rpms werent too high.
So what do we think now guys?
This makes me wonder that in the other 2 incidents that maybe my rpms were just hitting that point OR the speed was nearing that same point aswell, and that deceleration isnt playing a part as I was beginning to think.
Throw Back some info guys thx!