I wouldn't waste the cost of gear lube on an 8.5" ring-gear axle. They're wonderful for what they were intended for--compact and intermediate cars. GM didn't use 'em on full-size cars until full-sized cars were downsized to intermediate size and weight. GM should never have put them under full-size trucks.
Make the switch to a 9.5" ring gear axle. Twice as strong, and the G80 isn't a hand-grenade. And on the pickups, the brakes are better, too. You'll need a conversion U-joint, and new U-bolts.
Downside for the C1500s is that most 9.5s will have six- or eight-lug axles. Six-lug axles would be preferred. You'd either need custom 5-lug axle shafts and new brake drums, or you need new (rear) six-lug wheels; or six-lug wheels all around plus front rotors. I've never done the 9.5" axle conversion on a 2WD, but they're beyond easy with 4WD.
Seems to me that the switch from 28 to 30 spline on the 8.5" axle was in '88 or '89.
Make the switch to a 9.5" ring gear axle. Twice as strong, and the G80 isn't a hand-grenade. And on the pickups, the brakes are better, too. You'll need a conversion U-joint, and new U-bolts.
Downside for the C1500s is that most 9.5s will have six- or eight-lug axles. Six-lug axles would be preferred. You'd either need custom 5-lug axle shafts and new brake drums, or you need new (rear) six-lug wheels; or six-lug wheels all around plus front rotors. I've never done the 9.5" axle conversion on a 2WD, but they're beyond easy with 4WD.
Seems to me that the switch from 28 to 30 spline on the 8.5" axle was in '88 or '89.