I verified the required length needed by measuring the exposed thread on the stock bolt after placing it through the stock tube adapter. The required bolt for the 1401 is a 6mm x 1 x 30mm.
On another note, regarding changing of the transmission / hydraulic system oil, nowhere have I found any mention of also draining the rear diff by removing the drain bolts located at the bottom of each side of the diff. I drained mine and there was a considerable amount of oil in each side.
Regards, Yanmartyr
