Rear differential leaking from cover

[Damien8086]

Originally Posted by Motorfist

That drip looks like clean gear oil to me. Regular clean gear oil is a greenish brown in my experience. Any idea when the oil level could have been topped off, as in did you recently buy this truck and the previous owner filled it up before you bought it?

The fill plug on my 12 bolt is on the passenger side of the front/driveshaft side of differential housing, less than halfway up. It has a square head like a threaded pipe plug. You will have to crawl under the truck on the passenger side, in front of the tire to see it. I'd take a picture but my truck is at the shop getting an alignment after I rebuilt the front end.

Good luck!

Thanks for the additional info Motorfist.

Yes, I had had the rear differential worked on a couple of years ago (fluid change, cover and gasket change). It's only been driven less than 100 miles since that work was done.

This mechanic had the truck for months working on several different things. So far nearly everything he did has had to be redone.

[Motorfist]

I'm sorry to hear that Damien, but it seems to happen a fair amount. That's the beauty of this website though, you can learn to do anything you dare, yourself. Then if a repair goes bad you will learn from it and didn't pay someone else the labor $ to mess up your truck!

One thing that hasn't been mentioned is make sure you buy a gasket scraper to remove the old gasket and sealer from the housing and cover. Sounds like it might come off pretty easy but it's an inexpensive tool that can save you time and save the gasket surfaces form being gouged.

I don't remember who mentioned it above but making sure the covers gasket flange is flat before you put it back on is important.

[Damien8086]

I think I found a picture of the vent. Mine definitely does not have this.



Here is a link to where to buy it in case anyone who comes across this later needs one: https://www.summitracing.com/parts/rnb-14689

Now I am wondering about some other hoses that are hanging around on my truck and whether or not they should have a vent like this. I have one coming out of my radiator for sure that just hangs above the ground.

[Motorfist]

The radiator vent hose does not have a one way vent plug on it. You can install a surge/catch tank so excess antifreeze doesn't just puke on the ground but if the radiator is filled to the proper level (not full) and the truck is running properly, it shouldn't be much of an issue.

[garyd1961]

I couldn't find a gasket so I just used Permatex Ultra-Gray on mine and it hasn't leaked a drop.

[leddzepp]

Make sure your vent tube (hose) isn’t plugged up or you will have leaks again real quick.

[Wrenchbender Ret]

The diff. plug on my 72 w/ 12 bolt possi.
George

[Redneck Rydes]

The vent that is missing should be there,it will let air out,but was made to keep water out,especially on 4x4 when going offroading in the water

[Steeveedee]

Someone in the past took that hose on my truck and put another fitting on the sheet metal differential cover and connected the axle vent to that fitting, so it didn't have a vent valve. Since I don't plan on driving in deep water with my truck, I put a new vent valve directly onto the axle tube and capped the fitting on the differential cover. I'm open to being told that that is not recommended.

[71CHEVYSHORTBED402]

The shop that rebuilt my axle said to apply sealant on the cover only and no gasket. That's what I did and so far no leaks. Thin even bead around the perimeter and bolt holes too, and don't spread with your finger. If you decide on that, be sure to make up a couple of 5/16-18 studs to use as guide pins so the cover goes on cleanly.

For what it's worth, the cover I pulled had a gasket and sealant on the cover side only. That didn't leak either.

As far as the hose, keep it off the exhaust. Mine used a hose retainer on the front wall of the cross member located behind the axle, nearest the LH side of the truck (SWB). The hose didn't have a breather valve when I found it, but I added one. Ah, here it is.