I checked around and got some good advice regarding the hole. Early on the NP231 didn't have the hole. But later on Jeep put on their to better lube the gear as it spins around the shaft. So I called the mfr and they said their design requires no hole and they stand by it. So I called back the company who sold it to me and he is going to let me trade up to a Rubicon Express 1811 one. The RE1811 has the hole. I wonder who makes it for them. The main thing is it has a hole for lubrication like the AA SYE that I'm replacing. Not all SYE kits are equal!

1985 Toyota Pickup
1994 Jeep Cherokee Sport