Hey guys I have a 98 chevy blazer and noticed that there is a loud whining noise coming from under the truck sounds like itsfrom the back but i'm not sure. it gets really loud when i have the truck in park. any ideas what it could be.

 

Do you hear it when driving or just when the truck is sitting still or both?

 

could be the fuel pump?

 

the only time i notice it is when i'm sitting still or driving real slow like a couple mph I kinda thought it was the fuel pump but wanted to get somemore input on it.

 

That's exactly what my 99 sounded like just before the transmission went out. The sound was apparently coming from the torque converter which had been getting extremely hot. It lasted like that for 3 or 4 months and then finallythe trans would just slip. It happened at about 160k miles, so I wasn't too surprised. $1200 bucks at AAMCO fixed it right up.

 

If the sound is coming from the back area while in park and does not change if you put it into different gears, I would strongly suspect the fuel pump. Even a good one is audible to me. If you can hear it while moving more than ~10mph then I would not expect it to be the pump unless you've got really good ears.