Assuming that the transmissions' out-put shaft splines are not damaged in some fashion (look up the shaft splines with a flashlight!), by the manufacturer (not likely
, but possible) or that particularly being a likelihood from someone else previously improperly installing or removing a driveshaft, or one being thrown-out from especially some sort of driveline failure (I guess not since it's new
), and there is no other foreign material just stuck in the splines (male or female), then I would say, this presents as another example of why one shouldn't buy Summit 'cheap-brand' stuff! And particularly when considering how much one has spent on everything else for this conversion, why buy this cheap crap anyway?
This relationship is as it is termed: a "shaft & slip-yoke", and if needs to be just that, a 'slip-fit', no mallets required; otherwise the least that one might expect would be an excessive vibration generated, with several other detrimental effects of far greater repercussions being possible.
B.T.W. : perhaps it is just poor literature on the Summit site but "CAST" steel? The 'good ones' should be "FORGED" steel construction! But then, it's probably an 'off-shore', manufactured for less product, so what do you expect!
Scott.