Once it gets tight, a slow gentle push, with one hand while pulling gently with the other, and it should slide right through. It may be necessary to prevent the tubes from moving, by taping to a nearby harness. I will feed it into the front end of the shift console to e-brake tube, while gently pulling the wire out of the e-brake side with the other hand. Once the temp probe is out enough to feed into the rear tube inlet, the same right hand feed in, left hand gentle putt, also feeds it into the rear tube. Having someone there that is gently pulling it into the rear area really helps with this three handed operation.
The multi-wire harness is quite strong in the longitudinal direction, but can be damaged by a tight bend which could put a lot of strain on only a few internal wires. That is why we pass it through both tubes at once.
Slow and gentle is the secrete to no damage.