rear differental vent blowing oil

[ryecreek]

started bout a month ago.

oil is fresh no water not foaming

does not run hot normal driving empty 65 deg ambient diff temp runs 127 deg checked with a Blue Point gun

cleaned the vent tube end to end and starts blowing the very next day

any thing that causes this???????

my customers whine as it drips a drop or 2 on there driveways

 

[HBarlow]

Mine did the same thing awhile back. My mechanic friend who had serviced it finally concluded he had overfilled it when changing fluid.

 

[steved]

How do you know its not foaming?



The oil getting whipped into a foam is the most likely cause of a vent leak. I would change the oil (maybe even try another brand), and see if the issue goes away.

 

[amsoilman]

Most likely your diff is overfilled.

 

[steved]

FWIW:



I run over an inch over the normal full mark (which would be very difficult to do with a stock cover) using an ORU aluminum cover, and I have never had oil blow out the vent. The axle tubes are partially flooded at my current level.



I run 85w140 Royal Purple. I can, and occasionally do, drive upwards of 500 miles without stopping; which should show the overfill (in my case) being an issue.



I am in no way saying it can't happen, just that it hasn't in my experience... I have been running this way for well over 130k.

 

[Wingate]

started bout a month ago.

oil is fresh no water not foaming

does not run hot normal driving empty 65 deg ambient diff temp runs 127 deg checked with a Blue Point gun

cleaned the vent tube end to end and starts blowing the very next day

any thing that causes this???????

my customers whine as it drips a drop or 2 on there driveways

How about verifying the simple stuff first... Its the correct type and viscosity of gear lube?... I'm thinking 75W-110 Synthetic, or possibly 75W-140?... As for lube levels, that can be subjective... . I would possibly drain an ounce of oil out and see if it continues to puke oil. (I would use a oil sample pump or siphon pump) If you are using an aftermarket high capacity cover, you might consider draining out a couple ounces and drive it for a day or two. Ideally, you want to check it on level ground with the oil at ambient temps... When I installed my HY-Tec covers, I kinda cheated, I filled it pretty close to where I thought the full level would be, then got my trusty Snap-On borescope out and checked inside the diff... . to verify that the oil level was just into the bottom of both axle tubes... . Then marked the dipstick...

 

[ryecreek]

How do you know its not foaming?



The oil getting whipped into a foam is the most likely cause of a vent leak. I would change the oil (maybe even try another brand), and see if the issue goes away.

checked during a drive ASAP

 

[ryecreek]

Most likely your diff is overfilled.

1/4" below the hole

 

[ryecreek]

How about verifying the simple stuff first... Its the correct type and viscosity of gear lube?... I'm thinking 75W-110 Synthetic, or possibly 75W-140?... As for lube levels, that can be subjective... . I would possibly drain an ounce of oil out and see if it continues to puke oil. (I would use a oil sample pump or siphon pump) If you are using an aftermarket high capacity cover, you might consider draining out a couple ounces and drive it for a day or two. Ideally, you want to check it on level ground with the oil at ambient temps... When I installed my HY-Tec covers, I kinda cheated, I filled it pretty close to where I thought the full level would be, then got my trusty Snap-On borescope out and checked inside the diff... . to verify that the oil level was just into the bottom of both axle tubes... . Then marked the dipstick...

75-90 synthetic valvoline



factory cover

 

[steved]

checked during a drive ASAP

I restate... change the oil. If this condition started with the oil change, and everything else is constant, that leaves the oil. It might be simply off-spec?



As previously asked, what viscosity??

 

[amsoilman]

In a publication called "A Study Of Automotive Gearlubes", the Valvolene "SynPower" 75W-90 Synthetic gearlube was the very worst for Foaming Tendancies (ASTM D-892) of all the gearlubes tested. (14 tested)

 

[ryecreek]

In a publication called "A Study Of Automotive Gearlubes", the Valvolene "SynPower" 75W-90 Synthetic gearlube was the very worst for Foaming Tendancies (ASTM D-892) of all the gearlubes tested. (14 tested)

used it for 240k with no issues just all the sudden found its way out the vent are you saying a change in oil brands will fix my problem.



STEVED

i changed the oil after it started blowing out. cleaned everything out (including vent tube) put in fresh oil ... . Next day same deal bad enough to get on the back of my truck

 

[amsoilman]

are you saying a change in oil brands will fix my problem.

I just made mention of the fact that the brand and grade of differential oil you are using was the worst of all the other brands of that grade when it was tested for foaming. "CLICK" on the link and read it for yourself.

 

[Wingate]

75-90 synthetic valvoline



factory cover

YOu don't know a heavy equipment tech do ya?. . They may have a borescope you can borrow. You might attempt to do what I did, and use a borescope to verify exactly where the fluid level is in the axle tubes... Some parts stores will rent one to ya, but I'm not sure about the quality...

One other thing... . you said you were using 75W90 GL????... Although I havent bothered to read my owners manual, I thought the factory fill was 75W110?. And some people( like me) have opted for 75W140... . But I could be wrong,,, I've seen me do it!!!!. . You might check/verify the reccomended viscosity.

 

[mtnram]

a suggestion learned from my jeep project. After lifting it and rotating the pinion up to correct geometry issue it's common to get foaming.

A tablespoon or two of atf will eliminate the froth as it contains anti-foaming agents.

 

[steved]

YOu don't know a heavy equipment tech do ya?. . They may have a borescope you can borrow. You might attempt to do what I did, and use a borescope to verify exactly where the fluid level is in the axle tubes... Some parts stores will rent one to ya, but I'm not sure about the quality...

One other thing... . you said you were using 75W90 GL????... Although I havent bothered to read my owners manual, I thought the factory fill was 75W110?. And some people( like me) have opted for 75W140... . But I could be wrong,,, I've seen me do it!!!!. . You might check/verify the reccomended viscosity.

75w90 is the correct fill...

 

[ryecreek]

TTT

anyboby now of possible causes