Okay first off, when i'm at higher speeds, 60 and over when i let off the gas or go down a hill there is a vibration coming from the tranny (4l60e). I won't feel a thing a high speeds if i just keep going higher and higher, but the minute i let off the gas the vibration is horrid. transmission does leak a little fluid from the front but I can't see where from, but its not from the pan. Any ideas? Also i'm not getting near as good gas mileage as i should (around 10-15 on the highway, even worse in the city). I do have two different O2 codes an EGR flow code and a MAF code sometimes. These codes wouldn't make the car get that bad of gas mileage though would they? I did change out the coolant temp sensor in the waterpump and for about a week it stopped running rich and got about 25 mpg on the highway but now i'm back down to where i was. Could the transmission problem be causing worse gas mileage too? Thanks!

97 z28. Edelbrock throttle body and headers, k&n cold air intake, rear end and tranny work (dont know what kind) Thats all the guy knew when i bought it because he was selling it for his son.

 

The O2 sensors help the PCM control the air/fuel ratio. A problem with an O2 sensor can easily cause a major loss of fuel mileage.

 

I know but i'm getting 10-15 on the highway and around 6 in the city. They wouldn't make it get that bad would they? It has three different codes for the 02's and two of them are for sensor number two, but seeing as how my car doesn't have cats, I'm not really thinking those two codes are causing problems or am I wrong?