In my 64/98 I want to change the oil in the diff, but havent got a gasket if taking the diff apart, but is it possible get a hose in through the filler hole and suck it out with a vacuum pump, of will I have to remove the complete gear??

 

You could suck the oil out through the driain plug, or you could remove the cover and use RTV in place of a gasket.

 

I dont have a drain plug, or a cover, that is why I ask. I only have the filler hole on the side of the diff, and before jaking up the car my question is if it is possible to get the in to the diff through te filler hole and down in side the diff enought to suck the oil out. But if the only way to go is to remove the front of the diff, I will do that.

But a sealant like RTV would be sufficient if not having a gasket is good to know, thanks :-)

 

Yes you can pump the fluid out of the fill hole, however is it has not been apart in many years there will be some sludge at the bottom that cannot be cleaned out.

 

I had no idea that sludge would be created in a diff... Then I will strongly consider not cutting corners, and do it the messy way and open it op. Thanks

 

The old-style Olds/Pontiac axle doesn't have a cover. The whole center section comes out like on a Ford 9".

 

Yes its a chore,

Have to jack up the rear, remove rear tires and wheels disassemble the rear brakes remove the backing plate, remove the rear axles, remove the drive line unbolt the center section and loosen to drain oil into a pan then remove rear. clean out the muck at the bottom of the housing and then reverse the process filling with new recommended oil usually 90 weight.

Things to check while you have it apart
brake shoes or pads
axle bearings and seals
pinion seal

replace above as needed

This can turn into a MAW in a hurry

 

Sorry about the drain plug comment - I really thought I had typed fill plug.

 

Not so much sludge just fluid evaporation so it looses it viscosity and becomes tar again....plus contamination of metal from bearings and gear which become a silt of sort. lol. too much heat will do that to oil.

 

Okay, it makes sense. Thanks