Lag in acceleration 40-50 mph

2010 4.0 automatic with 165k on dash. Been noticing a lag when speeding up from 40-50 mph not all the time but when it does it I’ve been concerned. Been doing it for awhile. Truck shifts fine so doesn’t feel transmission related. Taking it to get looked at Monday at a local shop. Anyone else had this problem?

 

40-50 mph is sort of a no mans land with the transmission. The truck wants to shift into overdrive ASAP in order to get better fuel mileage. But if you're driving conservatively it will shift to OD somewhere at about those speeds and doesn't have enough power at those low rpm's. Your engine needs more RPM's to have enough torque and would be better off staying in 4th gear longer. When you're driving more aggressively and accelerating at those speeds the transmission stays in lower gears longer and doesn't upshift to OD until you're over 50 mph.

If I'm in a situation where I won't be driving over 40-50 mph for a while I shift into 4th gear and leave it there until I'm out on the open road and will be at speeds over 50 mph.

Not saying there isn't something else wrong with your truck but this is my 1st reaction.

 

Makes complete sense. I will say I’m guilty for babying my truck sometimes so maybe that’s where it stems from bc I notice when I give it some rev around those mph there’s no lag. I’ve heard these motors need some rev (correct me if I’m wrong)