I just found the problem. One of the zipties i'd used for cable management had snuck into one of the fans and was blocking it, while the other fan went crazy. When i sorted it out, they went normal.Which POWER SUPPLY unit are you using for the GTX 1070 ? List the make/model number. What happens to the fans, when the GPU is under load/stress ? Tried playing any games yet ?
Edit: What is the GPU TEMP and usage in IDLE mode ?