The oil pressure gauge goes from 0 to all the way up and the needle moves back and forth while driving it checked oil its good now its clicking underneath the car and it felt like the transmission was slipping could it be the oil pump going bad?

The computing system on your vehicle has no safe mode for running low on oil . The only thing that will happen is the check gauges light will come on.
The oil pressure gauge is an analog device that is located in the IPC. The oil pressure gauge is operated directly by the oil pressure sensor circuit. As the engine oil pressure changes, the resistance of the sensor and the current flow in the oil pressure gauge changes. The current flow in the oil pressure gauge causes the needle to move in order to appropriately display the engine oil pressure. A sensor resistance of 1ohms will display as 0 kPa (0 PSI) and a resistance of 88 ohms will display as 80 kPa (80 PSI ). The IPC also monitors the oil pressure sensor circuit and interprets the current flow in this circuit in order to determine when the engine oil pressure is too low. If the oil pressure is too low, the check gauges tell tale will turn on. The oil pressure sender is located on the left side of the 2.2L. The 4.3L engine, oil pressure sender is located at the top left side, near the distributor/high voltage switch.
Try disconnecting the battery cables an hold them together for ten minutes , reset ECM !

Replace the oil pressure sending unit, they are notorious for this problem.

Make sure there is spark at the plugs and fuel pressure at the fuel rail. The oil pressure guage will only come up when the engine starts.

If the needle is staying down and the motor is not knocking then the gauge is probably bad. If you run the engine with no oil pressure, then it will not last long. It will start knocking and ruin the engine. But yes the oil pump in in the oil pan. There is also a oil pressure sending unit that could be bad. It is located on the back of the engine.

First we would need to know when this occurs. Asuming the oil level is at the full mark!. If the pressure goes up during acceleration and down at idle when engine is fully warmed up, then this is normal. An engine requires 10 psi of oil pressure per 1,000 rpm ( ex. 20 psi at 2,000 rpm, 25 psi at 2,500 rpm, and so on ) . If the gauge is moving back and forth erratically at idle , i would say the gauge is bad. If it drops to 0 while accelerating I would say your oil pump is bad. If from time to time it seems to work and other times it seems not to work, I would say the oil pressure sending unit for the gauge is bad. If the pump failed you would start to here a Knocking noise from the engine in a short period of time. Use the above scenario's to narrow down what it may be.

is your oil level low? make sure it has enough. if that is ok maybe the sender or wire to it is bad

You'll need to determine if the oil pressure is actually changing, or if the sending unit or gauge is lying to you. Be certain the oil level is up to normal, then check the actual oil pressure with a test gauge. If the pressure varies (drops) at engine idle, perhaps your pressure bypass is defective, or perhaps the oil pump is worn. Testing with a known good pressure gauge should lead you in the right direction.

I think I'd be real tempted to check connection at oil sender, for clean and tight, and if that doesn't help, for the price, I'd change it, but not knowing exactly which engine you have, I couldn't give you a ballpark on oil sender switch. You can look it up or call autozone, or similar for price.

Replace the useless oil pressure sending unit with one from a early year such as 1986 .connect only the wire to the oil light.if you want a pressure gauge install an after market one..The stupid factory sending units can not rear pressure under 40lbs.at less than 40psi the light is on and the gauge reads 0 good luck carl

Any time the oil pressure is 0 you take a chance of locking up the motor. The only way to know for sure is to put a pressure gauge in the oil pressure sending unit port on the engine and see what the pressure really is. At that point you will either have the peace of mind in the knowledge that the sending unit is really bad and needs replacement or you can then contact a repair shop and tell them what your testing has revealed. I wouldn't drive or run your truck while the oil pressure is at zero.

Good luck