Trying to figure out if my stock axles are 28 or 31 spline. Just had the rear diff refreshed with all new bearings and seals. Shop owner told me that axle shafts are slightly grooved from the axle bearings and thus have a bit extra play. I can hear some bearing noise when I get above 40mph or so. Not real loud but not as quiet as I would like. I've been on several of the popular sites to price axles and I keep seeing both 28/31 spline shafts but no indication of which are stock replacement...

28 or 31 Spline for Stock 8.8"