I am going to change my rear axle oil for the first time. I have never done it before, it sounds like it is fairly easy. However I was wondering if anyone has any tips for me who has done it before. I have a 89 RS 305 TBI.

 

If it has a standaed differential then use any good GL4 or GL5 80W90 or 75W90 gear oil. If it has the Auburn differential then be sure to get 2 bottles of the GM oil additive and put it in the rear end before the oil goes in, or put them in the first bottle of oil.

 

ok thank you, but how do I know if it has a standard or Auburn differential??

 

Open it up and look in.

 

Remove the fill plug before you remove the cover.

I've heard of stories where guys had removed the cover only to find out they can't get the fill plug off. Now they're stuck with an empty differential.

 

RPO Code G80-Limited Slip Differential

 

When you remove the cover to drain the oil you will be able to see the differential. If it only has 4 gears inside it and nothing else then it's a standard differential. If it has 5 springs in it then it's the Auburn.

 

Hardest part will be getting the fill plug out.

Start there: BEFORE removing the cover. It kinda SUX to let your fluid all out, put the cover back on, then discover that you have no way to put fluid back IN.

 

I used Royal Purple with the additive already in it..
Also bought a new fill cap and while I had that diff cover off I painted it and it looks nice......

 

having been THERE before. you can fill it thru the vent opening. if you cant remove the fill plug. just sayin

 

Pictures??

 

Look at what? What will it look like depending on what it is??

 

A standard differential only has 4 gears and a shaft inside it. There are no clutches, cones or springs. The Auburn will have 5 springs and 2 preload plates along with the 4 gears and shaft. If it's a Gov Lock then it will have a governor, clutches and 4 gears and shaft.

 

Will royal purple's gear oil with additive work with 3.73 posi with motive GM gears?

 

Yes