I have a 96 cherokee sport 4.0 with 232,000 miles. lifter tick started several months ago.
Tried lucas oil,MMO, and seafoam which seemed to quiet it somewhat. Tried lighter oil and heavier oil. Changed pushrods, rockers and pivots. Right now using Rotella-T and wick 51515 filter. When I first start it there is no noise at all. After several minutes tick starts and after it reaches full operating temp it quiets somewhat but is still there. When I accelerate it quiets a little and is louder when I let off on the gas between shifts. Curiosly when I checked oil pressure with tester it shows 50-60 lbs at an idle. Makes no sense.

 

Lifter is worn out. When oil gets hot it is too thin to keep the leaky lifter pumped up. Oil pressure has nothing to do with lifters,they are self-pumping.

 

Are you sure its not an exhaust leak? That will make a ticking sound and the crack may open up when it warms up. 4.0 manifolds do crack from time to time.

 

Hot idle specs are 13 PSI oil pressure. If you have truly have 50-60 at idle, you have an oil passage restriction(s) somewhere.

That will cause a lifter tick, in that they are not getting an adequate flow and are collapsing.

 

Sadly the engine noise is common. The t6 is a great oil for the 4.0. My 211K 98 is loud til it gets hot. My 93 got the tick at about 95K and has 167K now still going strong.

Ron

 

Put a can of Restore in it and see what happens. Fixed 2 old 4.0s of mine with the lifter tick. What have you got to lose?