Erratic speedometer, it may read 20 to 80 mph parked, down the road it could be anywhere between normal and 100+. when it is a very warm day (70 or above it is normal) I have changed the speed sensor (vss) ... no change....It does not ever go to zero driving it. but sometimes goes to zero when I am stopped. very intermittent... any thoughts out there? "98 Jeep wrangler, 4.0 liter 5 spd.

SOURCE: speedometer stopped working

replace speed sensor

SOURCE: erratic speedometer with ABS and brakelight lit

same problem here, found 3 places that say it is the abs sensor:

Had this problem with my 1999 Ram 1500. There is a sensor at the top of the rear differential for the ABS system. That sensor went bad and replacing it took care of the problem. What caused mine to go bad was apperantly water got into the differential when launching and loading my boat. check to see if gear lube needs to be replaced also.
The answer above is perfectly correct. When the ABS sensor on the diff goes bad the speedo no longer will work, the odometer stops recording mileage and both brake and ABS light comes on. You also loose O/D or "Lock-up" in the torque converter. The sensor is inexpensive and can be changed in about 30 mins. Good Luck!

The fix for your truck is the ABS speed sensor located in the top of the differential housing , held in with one stud . Your speedometer is calculated through the ABS controller. Replacing that sensor will fix your problem.

SOURCE: Speedometer reading fluctuates

IMHO, I think that the broken cable is what is causing the problems. It "confuses" the programing of the CPU or computer.

SOURCE: oil gauge goes up and down.

If grounding the dash does not work, try putting a mechanical gauge on it and reading actual oil pressure. Pressure does change while driving, but should not wander. With mechanical gauge, check that running hot at idle (in gear if automatic) pressure should not drop lower than 15psi (I'd rather see 20) High reading should be around 40 -50 but no higher.Low pressure indicates a loss of supply or bad bearing on the crankshaft, high pressure may be caused by sticking pressure relief or restriction in an oil passage.

SOURCE: 2002 jeep wrangler oil pressure gauge drops

When the gauge is at 0, is there any noise from the engine (tick, knock etc?) I would have someone put a mechanical gauge on there and read true pressure.Your driving pressure seems OK but if the low number is "real" something is wrong!