my speedometer cable keeps breaking...

For some reason my speedometer cable keeps breaking... this is the 2nd one... any ideas? this time what happened was i was taking a right from a stop sign and i look at the speedometer and it is bobbing like crazy. from 10-40... i keep going (i didn't have a philips head to open and check) but w.e. i kept going it bobbed around a bit and eventually went to 0... i came home opened it up and the cable was still connected to the gauge. took off the cable twisted it to see if it would turn.. sure enough it did. i drove around with the cluster off to see if it would turn... nope it didn't and it managed to come up... 3 inches out of the housing.

Any ideas?

I think it wasn't tightened it enough, and the tip that goes into the gauge was chewed up. and frayed.
I really want to switch to an electric one at this point. but i want to keep the stock look.

So i pulled the gear end out of the transmission, and pulled the gear off... and when i looked inside the tip of the cable was in there... but it was completely frayed and messed up...

I didn't install the cable, the painter did; is there anyway to check? my old cable had a ton of oil/ lube on it when i'd pull it out of the housing, but this one really doesn't it has barely any.

I bought an entire new cable and housing from NPD. it was ever so slightly lubed. there was a sharp bed right before it would reach speedo head unit, it probably snapped there too.

It broke when i accelerated fast out of the stop sign. the whole way back home it made a grinding noise, it sounded like the cable had totally come out of the speedometer head unit and was instead turning up the against the back of gauge cluster, like grinding in. it got louder and faster as i drove faster, and slowed down as i slowed down.

I bought this: http://www.mustangsplus.com/xcart/product.php?productid=4098&cat=0&page=2

Btw: it worked for about 2 days or about 30 miles of driving.