ok i have a 94 1500 ram 4x4. it has a 360 and automatic trans w/ overdrive.
first problem-the transmission wont go into overdrive...everything works fine in the truck and shifts fine thru the first 3 gears but just wont go into o/d. i dont know if its the o/d button or actuator or something...but the tranny shifts fine through the first 3

2nd problem-when the gas gets low in the tank like a 1/8th of a tank or so it will start but runs terrible and has no power..but when you put gas in it it gets better..i still have enought gas because the gauge is right when i fill it up..what would cause this?
thanks for the help

 

I dont know about the gas problem but get ready to put a tranny in.I had one do the same thing O.D. was the first thing to go then the lockup converter then TOWTRUCK[:@]

 

I've got a 94 Ram that had the same od problem as your describing-3 different times. 1st time it was a bad brake pedal brake lite switch,the overdrive circuit runs thru the brake pedal switch to kick the tranny out of od when you press the brake pedal and the circuit in the switch for od was bad, 2nd and 3rd time the wiring harness plug that connects to the brake pedal lite switch came unplugged,it would not lock onto the switch and I ended up replacing the connector. Could be your dash od switch or a tranny solonoid also.Don't know what your gas problem could be.

 

Try replacing the gas cap. The fuel systems depending on a certain pressure, and if your truck starts running bad when it gets low, then I get you've got a small pressure leak in the system somewhere.

 

Another thing to check is your fuel pressure. Could be the fuel pump is getting weak. [>:]

 

For your second problem, I had the same thing happen in my 95. When driving with low fuel the truck would occasionally run terrible and bog down when the gas was pressed. I was told that the fuel pump needs to be submerged in gas to cool it down and when the tank is low, this isn't happening causing the pump to overheat. After years of having this happen, the pump will eventually start failing when overheated. Not sure if the info was true, but it sounded good to me. I replaced the fuel pump and the problem went away.

 

Yes, what you told was true. The fuel pump was already failing on my truck when I bought it in Florida. We had to stop before the tank got to 1/2 empty to fill up, or the truck would run poorly. Once we got back to Indiana/Illinois (this was in winter), the gas in the tank was cool enough to keep the pump running. I ran the tank down low that way before dropping it to change the pump.

Most people don't realize this, but ANY vehicle with an in tank pump uses the gas to cool the pump. That's why you're not supposed to run the ANY vehicle below a 1/2 a tank in the summer.

 

Concerning the fuel pump, it won't have to work as hard with a full tank of gas due to the higher level of fuel, or "decreased working head". All pumps will have a lower flow rate or decreased pressure at the outlet when they have to push the liquid higher in elevation. So as the gas level drops in the tank, the pump has to keep working harder to push the gas up to the engine. Over time, the pump will become less efficent. When the pump has to work harder, it will generate more heat, so it is important to keep it cool by keeping more gas in the tank.

 

There is a fuse for the Overdrive in fuse panel on the dash. Start simple. I loaned out my shop manual so that's all I can say today.

 

Another possibility regarding the fuel issue...

Couple of years ago I had a Mazda that would stall out when it was nearing 1/8 tank, did the same thing when I was taking a corner when the tank was between 1/4 and 1/8. Assuming fuel pump, I dropped the tank to look. Turned out to be red sludge (rust) on the bottom of the tank that would settle on the fuel filter screen and clog it. As long as there was gas in the tank the sludge was suspended/diluted enough that it didn't matter. Cleaned out the tank and all was well.