Front diff leaking oil out vent tube

[c502cid]

Truck is a 2003 2500HD 4x4, 8.1 Allison. When I bought the truck this month (had about 27k miles on it) I changed out all the fluids and filters. Filled the front diff with recommended 80-90 gear oil. I drove out to So Cal from Colorado through lots of 100+ temps at speeds of 70-80+ without a problem. One day last week I stopped to get gas and saw oil on my left front inner fender, and onto the suspension below. I know a little oil makes a big mess so I wasn't overly concerned. I finally found the source, the vent tube just above the mess on the inner fenderwell. I'm sure it was gear oil. I pulled the vent cap and it wasn't dirty or plugged. I just cleaned it off tonight so I'm not sure if it will continue or not. I might have overfilled the diff a little bit when I did the change, oil was still running out when I put the fill plug back on. I pulled the fill plug today but none ran out. Any thoughts on why it was puking out the vent tube?

[Roofer]

I remember reading about this. With synthetic fluid, the stock breather hose leaks a little on some trucks. I'm not sure why a 2003 would have this problem though. There is a different hose that the dealer has to fix this. One is black and one is white. I can't remember which hose is the replacement. Maybe a search will help you out.

[bigdogs]

White is the one to use with synthetic fluid, some 2003's had them (mine did) some don't and now it is the only one you can get.

[c502cid]

I filled it with dino gear oil as the manual called for, not synthetic. I put synthetic in the rear, but not the front.

[bigdogs]

My dealer changed mine to synthetic due to the cold weather here. I know they also suggest filling a certain measurement below the fill hole now, (unlike the old days when you filled it until it runs out).

[JimWilson]

I might have overfilled the diff a little bit when I did the change, oil was still running out when I put the fill plug back on. I pulled the fill plug today but none ran out. Any thoughts on why it was puking out the vent tube?

Most likely you put too much in. If it was still coming out of the fill hole when you put the plug back in you had too much in their. Perhaps the reason none came out when you pulled the plug after you saw the leak is because it all blew out the breather by then.

 

Clean it up real good and then keep your eye on it. Perhaps it leveled itself off by now and you won't have any more problems.

[c502cid]

That's what I was thinking. I cleaned it up real good and I'm just watching it for now. I guess I was just surprised it didn't do it when I was driving it through the Mojave desert and temps were 110+ and I was driving at 80mph.