It is in the center of the rear of the axle.
Remove rear axle cover, oil will drain out, reseal and install cover, fill fluid.Remove rear axle cover, oil will drain out, reseal and install cover, fill fluid.
The rear drive axle takes 5.5 (pts.) to fill.
To change the rear axle fluid you can remove the rear cover from the axle and drain it that way. If you don't want to remove the rear cover you can use a pump and a hose to drain it through the fill hole.
The fill plug is on the rear cover of the differential. Remove the rear cover to drain the fluid.
This depends on what Buick it is. Most do not have oil in the rear "Axle" as most Buicks of this vintage did not have a rear Differential. The ones that did need oil in the differential have a fill plug on the rear cover or the side of the case and this is where the oil is poured in. Follow the instructions in the owners manual to get the correct level.
The fill plug is in the middle of the cover on the center of the axle.
The rear axle fill plug is the rubber plug in the rear differential cover. Fill the fluid to the bottom of the hole. 75w90 or 80w90, if posi it requires a limited slip additive.
take out the plug and fill it till it comes back out the fill hole
plug is on the left front of axle housing. take a 3/8 drive to remove
there is a gearbox in the middle of the rear axle with a drain nut on the bottom and a fill nut on the top
The rear axle will hold about 2.5 quarts.