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Axle vent related question...

2135 Views 17 Replies 8 Participants Last post by  TheHops
So, I finally got around to installing my Cajun axle vent kit. While I was under there, I noticed something that I should have noticed a long time ago...I have no axle vent at all. :bangit: It's just an open, threaded hole. I just changed my front and rear diff fluid at 31,567 miles, on November 4th. I just broke 33,000 on the odometer. How I didn't notice that it was missing when I was under there before, I have no idea.

I checked my seals while I was under there and everything looks good. There was no seepage or anything that I could see, though there was obviously a trace of fluid on the axle just below the vent.

Basically my question is this: On a scale from 1 to *string of expletives* how concerned should I be? I am aware the diff fluid change is a 30,000 mile maintenance item but, considering I have almost undoubtedly had at least some degree of water intrusion since November, should I do a full drain and fill of the rear diff again? I'm not as worried about pressure buildup obviously because, well...there wasn't even a vent to stick! Would the water eventually evaporate? Would I be alright with just topping off what fluid I may have lost?

The fluid trail I saw was nasty. It looked and smelled more like the old fluid. I can't imagine the brand new royal purple I put in would already come out looking like chocolate milk, and smelling like death.

In your opinion, what is the best course of action to take? Thanks ahead of time guys!
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You could drain the fluid and if it looks ok just put it back in. I would put new fluid in if it were mine though.
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I have not heard of the vent totally missing but I have heard of guys getting a replacement axle from the dealership and the idiot mechanics leaving the plastic plug in the hole and not putting a vent in there. Your case....I would change the fluid
I have not heard of the vent totally missing but I have heard of guys getting a replacement axle from the dealership and the idiot mechanics leaving the plastic plug in the hole and not putting a vent in there. Your case....I would change the fluid
I kind of couldn't believe it myself. I knew where the vent was supposed to be, and kept scanning between the rear diff and the passenger side leaf spring but...all I saw was that hole. I was kind of in denial for a few minutes, until I put the cajun vent in there and tightened it by hand. While I'm on that note, kind of a side question: Should the bottom of the nut on the vent be flush with the axle? I can still see the top thread or two, but I was torquing it pretty hard and wanted to make sure I wasn't going to damage anything.

At any rate, looks like I'll be picking up another $50 of fluids next paycheck... :crying: but I guess I'd rather be safe than sorry.
The Master Tech that put mine on said that the vent piece itself the threads get "bigger" at the top than the bottom, so he couldn't tighten it all the way down, less risking stripped threads. The pipe thread sealer put on it and tighten by hand has done fine for me.

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the term is "pipe thread" they are tapered so that they get bigger and seal the hole as they go in, if tightened til the threads go away it will probably break before the thread disappear.
the hole they go in is also tapered.
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Just a quick followup:

So I did decide to just go ahead and change the fluid out again. I'm glad I did. This is 75W-140 Royal Purple with no more than 3,000 miles on it...it came out looking like frothy sludge.

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That... is disgusting... My OEM with over 50k miles on it didn't even look like that...
That... is disgusting... My OEM with over 50k miles on it didn't even look like that...
Mine looked worse from my previous 30k mile change, but that's probably because there was no vent in it at that time either and I didn't notice...I'm just glad that I bought the vent kit when I did, otherwise I never would have gotten under the axle to take a look. It doesn't appear that any actual damage was done, so I can't complain...though I am very curious as to why the hell there was no vent in the first place.

I'm probably going to let this ride for another 1k-2k miles and recheck the new fluid to make sure it's squared away.
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Good idea.
I'm probably going to let this ride for another 1k-2k miles and recheck the new fluid to make sure it's squared away.
I'm not sure I would go that long. Couple hundred miles and I would put fresh fluid it. But I have a case of that crap to go through so a couple bottles doesn't bother me.
I'm not sure I would go that long. Couple hundred miles and I would put fresh fluid it. But I have a case of that crap to go through so a couple bottles doesn't bother me.
Maybe my last post wasn't clear. My fault.

I'm saying, I'm going to drive another 1,000-2,000 miles on the brand new fluid I just put in a few days ago, before checking it again. Not on that old, nasty crap. No way I was letting that stuff slosh around in my rear diff after I saw how it looked! Now that I have the cajun axle vent on I'd say it's safe enough for a decent distance.

Royal Purple is ~$20 a quart, but I've had good experiences with the brand. A small price to pay for not having my rear axle blow/seize up, but certainly not cheap!
I understood what you meant. And I still wouldn't run the fresh fluid that long. Go to Wal-mart and buy their brand of gear fluid. Run it for a 100 miles, drain it and then put in the good stuff.
Interesting. Is that what's recommended each time you change it in order to help flush out the old stuff, or is that just for my case considering the circumstances?

At this rate I'm going to need to take out a line of credit just to fund my apparent gear fluid addiction. :hahano:
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I run Valvoline 75/140 synthetic in mine and have all my vehicles for years with no issues. I do properly maintain and change the fluids including radiator coolant more than the average guy though. I can't for the life of me go 10,000 miles like suggested by some of these high end motor oils between changes. 5000 miles is tops for me even with synthetic oil.
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Interesting. Is that what's recommended each time you change it in order to help flush out the old stuff, or is that just for my case considering the circumstances?

At this rate I'm going to need to take out a line of credit just to fund my apparent gear fluid addiction. :hahano:
This is just for your situation since you appear to have some contamination.
At this rate I'm going to need to take out a line of credit just to fund my apparent gear fluid addiction. :hahano:
I was going to say to take your wife out for a nice dinner..... since you just saved yourself a couple grand on a new rear end! :big_grin::big_grin:
I was going to say to take your wife out for a nice dinner..... since you just saved yourself a couple grand on a new rear end! :big_grin::big_grin:
Don't encourage [the girlfriend] her. :bangit:

Besides I'd rather spend that dinner money on a new UQ resonator, or some LED headlight bulbs. Priorities, you know! :devil:
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