Stephen0523

Hello. This is probably a stupid question but I need to ask!
I am going to change the oil in my rear differential.
What I am wondering is can the car be backed up on ramps or does it need to be level?
I am going to remove the cover, clean it and install a new gasket.
Also would it be better to use synthetic or regular Differential 80 oil?

oldcutlass

I prefer jack stands, then you can rotate the wheels and inspect the gears and bearings. I would use 80/90 weight gear oil.

Stephen0523

Hi OldCutlass, so are you say 4 jack stands to bring the car up level?

oldcutlass

Just 2 in the rear to work on it, level the car to fill. If its a posi, you need the posi additive for the clutches.

Stephen0523

Gotcha, so I might just raise it up fully level to do the whole job.
Now how would I identify if it has Posi rear end?

oldcutlass

Do both tires leave black marks and smoke excessively when you do a burn out?

Stephen0523

LOL, I have not tried that as I just inherited the car from my uncles.
So tomorrow I will find a quiet country road and light them up!

oldcutlass

You can jack the rear up and see if both wheels turn in the same direction when you spin one or the other.

MDchanic

That is the quieter way.

And any good gear oil will be fine - 90 weight, 80w90, etc.
Synthetic won't hurt, but is completely unnecessary.

- Eric

Fun71

Just make sure the transmission is in neutral or else the differential action will cause the wheels to spin in opposite directions due to the driveshaft being locked.