It might be the motor.  You can check that it is getting the right voltage - http://www.solidoodle.com/how-to-2/troubleshooting/ (the section about the stepper chips).

As far as I know any kind of shifting will either be the motor or the belts / set screws.

Sounds like this guy had the same problem...

http://www.soliforum.com/topic/1625/lay … -printing/

The best way I have found to check for slack/backlash/loose screws/play in the X axis is to simply grab the collar on the stepper motor and turn the motor by hand (make sure the motors are off, even so it is quite stiff). You only need the tiniest of movement on the motor end and then look at the pulleys or carriage. You should see the instant you start to move the motor that the farthest point turns, for the X axis I just use the front pulleys as reference as they are easiest to see.
Just rock the motor back and forth and it should be pretty obvious if you have a problem.
I have been able to reduce errors in a number of places by doing this as you can clearly see where the problem is.

Clearly this won't highlight if the is a sticking point on a shaft but it you at least make sure you test the motor over one turn and that everything moves as it should you can be sure the printer is trying its best to move where it is being told.
I guess if you wanted to manually check for sticking points you could undo the setscrew on the motor, the carriage should move freely (I've never had to do this yet) and you would then be able to feel for any tight points as you spin the pulley on the motor shaft. You would be able to feel a pinch point much easier by hand rather than using gauges or measurements.

I have removed the y axis rods, tensions, testing lube set screws deburr rods, rotate them everything. the thing flows effortlessly I have set my tension front and back of the carriage both sides within .1" deflection of each other tight and loose. I removed the z nuit put it back z wobble etc. I have gone over 1 week and half a spool of plastic and every print around 8 now maybe 20 layers just blows up the model. It will look perfect then bam immediately starting the next layer it shifts back and back.

I set it again etc and it will shift plus/minus a few layers. no way the rod align,ent is this sensitive or I f up this much for a week. It runs and looks better then I remember it new. back rod doesnt shift the cal cubes are dead on. I give up yet again anotehr wasted night with I thought success only to have my last 2 models be totally the worst ones again.

I wills et flow rates again and relevel the bed again, maybe I am missing something

but anyone have idea if SD will take a refund? or take this back and fix it?

If you want to get the pulleys on your own, these will work - https://sdp-si.com/eStore/PartDetail.as … roupID=347

They are MXL pitch timing pulleys with 18 teeth, 6mm bore, 2 flanges and hub. about $5 each.

Sorry I just realized the back three pulleys have an ID of 6mm the rest have 5mm ID, So if one of yours is slipping the only thig is try to glue it or call SD to get a replacement.

really? I can spin the collars without the pulleys and seperate them

That may be the cause of your problems. They are supposed to be fixed together, the whole idea is so you can tighten the setscrew on a shaft and the belt will not lose position relative to the shaft. Since these collars are aluminum and the pulleys are composite they are pressed together and usually glued with some sort of loctite.