Long as I've owned this 4.0 I've never really paid attention to the oil pressure gague. So whatever it's normal operating psi is I just don't know. Recently I noticed when pulling a moderately heavy empty single axle trailer I was showing 80 (max) on oil pressure all of the time. I thought that might be because of all the extra weight. But after observing my oil psi without the trailer I"m not so sure. Afterwards, during a very easy acceleration up to 60 mph without the trailer the oil pressure maintained at least 80 (max) and often moved above the gague's limit to around 90. Did notice it slipped down to around 60 for a bit but that was only during coasting and braking. In general, my oil psi is pegged close to 80 almost all of the time.

Is this normal?

 

Is this normal?
No. Your gauge is wrong.
Check it with a mechanical gauge.

 

X2 on checking with a mechanical gauge (real easy to do). 90 percent probability that the oil pressure sender unit is shot. Also very easy to replace too.

 

Time for a new sending unit. When your gauge will read at max pressure that means your sending unit is shot.