Axle Vent Mod Problem

STRIPER1 · 10-06-2006, 11:23 AM

Two months ago I performed the axle vent mod. which involved running gas line tubing up behind the tail light and ending in a cheap fuel filter. The mod. seemed to work fine and I've had no issues until today. After a trip of 1.5 hours, i notice a 6 inch wide puddle of dif. fluid under the tail light. This is the same trip I have driven twice per week since performing the mod. This is the first time the fluid has leaked out past the filter.

I have a 2004 (only 10,000 miles) with a PML extra capacity cover and I checked the fluid level when I did the vent mod and everything was perfect.

Any ideas what is happening here? Could capilary action bring the fluid from the dif. all the way up 6 feet of tubing? Could the dif. be "grenading" and overheating to the point where the fluid expanded enough to force it all that way? (I have heard no strange noise nor felt anything strange while driving the truck.)

Thanks For your help and input.

**walleeme** · 10-06-2006, 11:32 AM

Maybe the wind whistling by the open end is creating a vacuum.

titanmike · 10-06-2006, 01:16 PM

I was just about to do this mod. I wonder if it is a sign of the rear end getting ready to go. Did you fill the dif back up and drive it yet and see what happens?

Herbpov · 10-06-2006, 01:24 PM

Most likely the same problem that is causing the rear seals to fail. But, what is it??

bestatchess · 10-06-2006, 01:48 PM

Quote:

Originally Posted by STRIPER1

Two months ago I performed the axle vent mod. which involved running gas line tubing up behind the tail light and ending in a cheap fuel filter. The mod. seemed to work fine and I've had no issues until today. After a trip of 1.5 hours, i notice a 6 inch wide puddle of dif. fluid under the tail light. This is the same trip I have driven twice per week since performing the mod. This is the first time the fluid has leaked out past the filter.

I have a 2004 (only 10,000 miles) with a PML extra capacity cover and I checked the fluid level when I did the vent mod and everything was perfect.

Any ideas what is happening here? Could capilary action bring the fluid from the dif. all the way up 6 feet of tubing? Could the dif. be "grenading" and overheating to the point where the fluid expanded enough to force it all that way? (I have heard no strange noise nor felt anything strange while driving the truck.)

Thanks For your help and input.

I doubt capillary action is to blame, nor do I think that the synthetic gear oil expands sufficiently (the boiling point is pretty high) to run out of the vent. I think that heated air in the differential is expanding (pressure increase) and forcing fluid out of the vent. This may have only happened this one time because gear oil was in the portion of the axle housing near the vent, whereas typically just air goes out of the vent.

But I would get one of those IR thermometers and keep track of the diff temps just in case.

Other thought: If there is water in the differential (condensate or leaking in somehow from deep water crossing) the water could boil, flash to steam and blow diff fluid out.

skyhammer · 10-06-2006, 02:57 PM

Striper1Quote"This is the first time the fluid has leaked out past the filter."
You put a filter on the vent tube line? Perhaps that is the problem, the filter is allowing pressure to build up.

titanmike · 10-06-2006, 03:19 PM

If he used a cheap fuel filter like most did i doubt that could cause it to build up any pressure. They have to be basically free flowing to allow fuel to pass through them.

Herbpov · 10-06-2006, 04:15 PM

Quote:

Originally Posted by titanmike

If he used a cheap fuel filter like most did i doubt that could cause it to build up any pressure. They have to be basically free flowing to allow fuel to pass through them.

I doubt a fuel filter would let 75w-140 gear lube to flow freely. If anything the filter would clog up. Most likely a build up and then it finally let go. Filter might have failed or fell off. My front breather has a drop or two of oil on the fender well. I'm sure the same is happening in the rear. Better off without the filter.

Chris03hd · 10-06-2006, 04:48 PM

Never seen this mod posted here before.... benifit?

skyhammer · 10-07-2006, 12:07 PM

Quote:

Originally Posted by Herbpov

I doubt a fuel filter would let 75w-140 gear lube to flow freely. If anything the filter would clog up. Most likely a build up and then it finally let go. Filter might have failed or fell off. My front breather has a drop or two of oil on the fender well. I'm sure the same is happening in the rear. Better off without the filter.

Exactly, why would you use a filter on the vent tube? The front diff. just has a vent tube with no filter. What would be the purpose of a filter on the vent tube. There is no return line for the vent tube to send the fluid back into the diff. Therefore, it seems that adding a filter to the vent tube would defeat the purpose of the vent tube by blocking air flow.

*tlmaniac* · 10-08-2006, 07:29 AM

the filter is used to kepp trash out of the line.try using a cheap pvc valve they are on way check valves bassicaly and if the oil does get to it from air blowing across it and creating a vacum it wont be clogged the first time.

kartman · 10-08-2006, 07:35 AM

Quote:

Originally Posted by skyhammer

Exactly, why would you use a filter on the vent tube? The front diff. just has a vent tube with no filter. What would be the purpose of a filter on the vent tube. There is no return line for the vent tube to send the fluid back into the diff. Therefore, it seems that adding a filter to the vent tube would defeat the purpose of the vent tube by blocking air flow.

To keep dirt, dust and other junk out of the diff.

Chris03hd · 10-08-2006, 07:48 AM

Should I do this mod to my 06 Armada? Still have no idea why its even being done...

Paulphilly · 10-10-2006, 02:02 PM

I did the mod a few days ago and noticed a 8" puddle of fluid in my driveway today. Should I remove the fuel filter? Is this causing the backflow of fluid? Man, this sucks cause even the stock vent plug would leak. What should I do?

Chris03hd · 10-10-2006, 04:55 PM

Thanks for all the answers...