No 4th gear or down shift

89xj 4.0 auto 4wd 220,000 mi. running strong. All of a sudden I have no shift to 4th or OD?. Fluid good. trans fuse good under glove compartment. Took fuse out and manually shifted 1-2 3. Would not shift into 4th or downshift. I need help. I drive 45min. one way to work at 2400rpm. Gas is breaking me.
THANKS

What speed does 2,400 RPM yield? That doesn't seem high to me for highway speeds. Maybe you're getting overdrive and just don't know it?

Try adjusting the NSS and testing the TPS. Both have input to the TCU for shifting and for Torque Converter lockup. Failure, mis-adjustment, and damaged or poor wire connections can cause transmission issues. The NSS can be disassembled and cleaned.

Use the Google and find the JEEP AW-4 Service and Diagnostics Manual. Follow the trouble shooting charts and perform some diagnostics tests.

You may be getting 1,2,3 and 4, and not getting TC lock up!!!!

Have you tried disconnecting the TCU fuse, and then use manual, 1-2 for 1st, 3 for 3rd and D for 4th? That verifies the 4th gear operation and mechanical/hydraulics of the transmission, by passing the electric controls.

Also check the TCU fuse, and the TPS is one of the usual suspects for odd transmission shifting on 87-90 year Renix jeeps, so is a loose or bad ground on the sensors, especially the TCU side of the sensor. Also there is a white brake switch, upper switch way up above the brake in the dash that controls TC lock up.