Need some help with 4wd1

Im new to this stuff but not to RC. I work in a hobby shop. Im geting into robot. I got the awd1 3 days ago. got it working with my DX7 spektrum radio. But when i go backwards the left side gos fast but the right side gos slow. When i go forward all the motors go the same speed. when i turn left the motors go the same speed when i turn right the 2 right motors go slow and the s left motors go fast. Here is what i got. If you can help thank you.

spektrum dx 7
sabertooth 2x12
4 geared motors 200rpm 12v
11.1 lipo

how about some wiring pics and code then we can see whats going on but from the sounds of thinks and my rc battle bot i would say check the wiring between the microcontroller and rc reciver.
regards
Codemaster