glitching with mmm combo

[hendo6682]

Hey guys, I recently put a mmm combo in my e-revo and I am having some problems with glitching when the truck is about 75 feet away. It runs smooth as buttter when it is within 75 feet of me but when I drive it a little ways down the street, it stutters. I am guessing this is not cogging because it runs so smooth when it is close to the transmitter. I have the RX antenna coming straight out of the top of the receiver box. I shortened the motor wires as short as I can and have them still reach the ESC and it does it no matter what my gearing is. My setup is:

MMM combo
Spektrum DX2.0
2 Zippy 3s1p 20-30c 5000mah in series
21/65 gearing

Do you guys think I need a better TX/RX? I was thinking about buying a DX3R but I don't want to have the same problems with that system. Thanks for any imput.