Is there even a fill plug in the u-joint housing on the 4-speed? If so, I'd put 1/2 pint in there, maybe a little more for prelubing the u-joint. The rear bearing on the 4-speed is directly between the u-joint housing and the main case, so excess would run thru the rear bearing into the main case. Then put the rest of 6 pints in the main case. The service manual specifies 6 pints to fill the 4-speed. On the 3 speed, the u-joint is further from the main case, which is why the manual says to add gear oil to the u-joint area. Maybe it's not critical in the 4-speed because lube will get thru the rear bearing quicker so it provides lube to the u-joint sooner.
