I have a 69 bop 12 bolt with posi on my 69 cutlass. When I pull on the axle on the drivers side I have no movement at all but when i pull on the passenger side it moves in and out about 3/16 of an inch. Is this normal or what could be worn out. I,m no mechanic but i'm planning on taking the car on a 6000 mile road trip and just want to be sure it's roadworthy. Any information would be appreciated. Thanks

 

There's no such thing as a "BOP 12-bolt" axle. Unless your car was built in Canada, what you have is the Oldsmobile-only Type O axle. This has twelve bolts on the cover but only ten bolts on the ring gear. It uses bolt-in axles that are retained at the outboard end by the pressed-on bearing. That much end play sounds excessive and should be checked before you travel.

 

If this is an O-Type 12 bolt rear, the axle shaft is held in by a 4-bolt retainer just behind the wheel flange. The retainer is held on by the pressed on axle bearing, so the only things that could be worn are the bearing or maybe the shaft itself - the inner bearing race sometimes spins on the shaft and "grooves" the area where the bearing rides.

It's easy enough to pull the shaft in order to look.

 

3/16"is about 3/16" too much
Remove wheel
Back off brake star adjuster thru inboard access slot with 2 tools per CSM procedure
remove drum
reaching thru the axle flange holes, remove the 4 nuts holding axle retainer to housing
get rags/ paper towels handy
pull axle shaft out, watch for oil spillage
normally beware touching the seal, but you putting a new one in anyhow right?
catch spillage with rags
rags make handy thing to touch the axle with as you remove it also, that oil is STINKY.

Then inspect and replace the bearing and shaft as necessary
You may wish to start your axle search right now- even if you don't need the shaft right NOW, your car will someday.

Count the splines, and measure the length in the usual manner [I am not schooled in that procedure- one end is obvious, the other end less so].