I've done some research on the correct procedure to replace the rear diff cover but I do have one question. I have a 2001 Blazer 4wd. It looks like the gear oil goes in an opening on top of the differential with a breather tube attached. My guess is you remove the breather tube and fill it with 80w-90 gear oil. My question is, how do you know when it is full? Will it star to overflow? Thanks for the help!

 

Gear oil is not added through the breather tube. There is a fill hole on the front of the diff above and to the right of the drive shaft. It has a square dimple, which will fit a ratchet. I think it's 3/8" but if I'm wrong it's 1/2". Either way it's a standard size.

It's a good idea to clean the area and remove the fill plug before you remove the diff cover. that way you don't have to worry about the plug being seized or getting grit into the new diff fluid accidentally when you remove the plug.

Once you've replaced the diff cover, then you fill with diff fluid to the level of the bottom of the fill hole. If you fill through the breather tube you run the risk of overfilling.

 

I realize it's not added through the breather tube but thought it was added to the area that covered by the breather tube. Below is what I'm referring to. Is that correct? I'm not sure what is meant by removing the fill plug?? Thanks for the help!

 

Tech Article time... Rear Axle Service

Another 15 months and this one will be a decade old!

 

Thanks Swartlkk! I did already see that article but thought maybe yours was a different year. The pictures I attached was off a video I found on my exact year. I'm guessing they were not filling it at the correct spot then?

 

There is definitely a fill hole just like in the article Swartlkk posted. You're best off following the manual. Filling through the breather hole will likely result in overfilling the axle.

 

Thanks again guys!! Appreciate it!

 

Thought I'd post the before and after pic of the rear diff cover replacement. As you can see from the before picture it was in bad shape. When I ordered the cover and gasket I also ordered all new bolts and I'm glad I did. They were rusted really bad. I also sprayed the outside cover with an enamel paint to hopefully help with future rusting.

Before:


After:

 

I got the new cover with the fill hole in it. Will have to get a photo.

 

Where did u get the cover with fill hole?
This is going on my list of things to do...