What oil in a guv-lock rear?

[Bonnewagon]

I just swapped my rear gears around from 2:73 to 3:23. This time I used a GM guv-lock part time posi. None of my manuals cover this type carrier so I don't know what kind of oil it needs or if it takes the "whale oil" additive. I think they mostly came on F-bodies, Blazers and S-10's. Does anybody know?

 

[Bonnewagon]

Never mind. PontiacGP sent me this from a GM service bulletin.They specify GM's own GL5 which is probably more expensive than Chivas Regal. The use of any additive in locking rear axles (G80) is not recommended. Rear axle additives are designed for use in limited slip differentials which are normally installed in cars. All light duty trucks equipped with RPO G80 make use of a locking differential and the use of additives will delay the engagement of the locking mechanism and may decrease axle life.