Thank you @67GTA This is very helpful. I was leaning toward upgrading the fittings and given the feedback from Rick, it sounds like the majority of contact was coming from an oversized fixture mounted to the top of the diff cover. I am certain a solution can be made. Also, great insight on the custom hose with heat shielding, hopefully you can find your DYME invoice to simplify the process. It is good insurance given the harsh environment under there.

If you have an image of yours in its installed position, it would be great to have reference photos to see how you routed your hose

cholmes1 said:

Thank you @67GTA This is very helpful. I was leaning toward upgrading the fittings and given the feedback from Rick, it sounds like the majority of contact was coming from an oversized fixture mounted to the top of the diff cover. I am certain a solution can be made. Also, great insight on the custom hose with heat shielding, hopefully you can find your DYME invoice to simplify the process. It is good insurance given the harsh environment under there.

If you have an image of yours in its installed position, it would be great to have reference photos to see how you routed your hose

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Here’s a screenshot of the configuration. The order number is on there too, so Brendan may be able to replicate from their records as well.




I won’t be around the car for a couple weeks, but will try and get a some reference pics in early July.

cholmes1 said:

Thank you @67GTA This is very helpful. I was leaning toward upgrading the fittings and given the feedback from Rick, it sounds like the majority of contact was coming from an oversized fixture mounted to the top of the diff cover. I am certain a solution can be made. Also, great insight on the custom hose with heat shielding, hopefully you can find your DYME invoice to simplify the process. It is good insurance given the harsh environment under there.

If you have an image of yours in its installed position, it would be great to have reference photos to see how you routed your hose

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Another note on this - I’m using the port circled in red on the watts link cover in lieu of the one on top. Cortex v1 cover didn’t have the top vent port, which was the location on the stock Boss cover that was tough to get low enough to not interfere with the Bob’s can.

Yes. That is the tricky part on the Boss. I will need to find a very low profile AN fitting to go up top. Hopefully that, paired with your larger cutout idea, and it should give the space needed for full suspension articulation.

Not crazy about the can in that Cortex pic. Drains downhill. This axle will vent. It'll work, you just gotta stay up on the checking/draining it. Here's my completely custom pieced together setup on my '12 GT. Now that I know this axle is holding pressure even with the stock vent, I'll probably add this same setup to the Boss. I like it.

BackInBlack said:

It's correct. In Boss cars the vent is on the top of the diff cover. It makes seepage a little less likely. The stock GT diff cover doesn't have this feature so on those cars it's on the axle.
View attachment 110758

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My car doesn't have the two fill plugs (drain and I assume fill?) like that. Did you add those yourself?

galaxy said:

My car doesn't have the two fill plugs (drain and I assume fill?) like that. Did you add those yourself?

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No, it's a FRPP Boss/GT500 diff cover. I just grabbed the photo from a product review.

The bottom hole can be used for draining, but IMO it's a bad idea. If there's any metal bits or other crap in the fluid it'll mostly be at the bottom, and you can't get all of the fluid out that way. As for filling via the top hole, I'm pretty sure that'd overfill. Those holes are meant for a cooling system or an expansion reservoir.

BackInBlack said:

As for filling via the top hole, I'm pretty sure that'd overfill. Those holes are meant for a cooling system or an expansion reservoir.

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It’s actually made for filling, but obviously not up to that level. You’re supposed to remove the factory fil plug on the front of the axle to monitor the quantity while you add fluid in that top hole. Ease of service, but it doesn’t change the required fill level. I have this one and that’s per the instructions.

A clean install @BackInBlack but once you make the decision to mount in the trunk the options are pretty limitless in terms of reservoir options and mounting locations. For those wanting to avoid the interior entirely, and ideally not drill new mounting holes, it is a different challenge.

I use the old “turkey baster” bulb vent mounted on the top of an FRPP diff cover and that’s done the trick for me. But it appears that bulb vent is discontinued and Ford came out with this tube instead? This might be a good easy first step to try?


Btw, I found the stock small metal vent to be pretty constrictive even when clean and new. Maybe I just got a bad one but it was hard to blow air through it.

Thank you, @stevbd I was unaware that Ford offered what amounts to an extension tube. Not certain how effective it would be on the track, but it would certainly allow a bit more leeway for expansion that the OE setup.

I was unaware also. Seems Ford has taken a new swing at this since I last looked at this issue.

I just read the reviews in the link and people complain that it breaks when the suspension compresses on a lowered car.

stevbd said:

I use the old “turkey baster” bulb vent mounted on the top of an FRPP diff cover and that’s done the trick for me. But it appears that bulb vent is discontinued and Ford came out with this tube instead? This might be a good easy first step to try?

https://lmr.com/item/LRS-4022AA/ford-mustang-8-8-rear-axle-housing-vent-hose-kit-86-14?utm_source=google&utm_medium=cpc&gad_source=1&gad_campaignid=20122150534&gbraid=0AAAAAD62FUyPfCHeiA8sPSVCqudGhO5do&gclid=CjwKCAjwgO7RBhBKEiwAZNP85lpvU0sKhQphnZUp1BKbRImEftQIHSD6plVzJpYXC-KvqZmCp0X2kxoCBrUQAvD_BwE

Btw, I found the stock small metal vent to be pretty constrictive even when clean and new. Maybe I just got a bad one but it was hard to blow air through it.

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I've seen that. That kit was the fix offered for TSB 14-0046 (leaky axle TSB)

Well, I still don't think my brand new car is venting. I was installing a catch can like on my red car (above) anyways, but after a few drives this week, I took the plug out of the axle to start fitting up some hoses and when I pulled that plug, pshhhttttttttt....air. And it had been sitting for several days too. So my axle is clearly building up pressure even after some normal driving, and two, it must be sealed pretty damn good because it's holding good pressure for daayyyyssssss. I figure it's a matter of time before it starts puking, so I'm putting in a catch can system and be done with it.

Random thought though - that axle isn't supposed to have some pressure is it? I wouldn't think so, but not sure. Or does the factory little vent think only release pressure above a certain value?

galaxy said:

Well, I still don't think my brand new car is venting. I was installing a catch can like on my red car (above) anyways, but after a few drives this week, I took the plug out of the axle to start fitting up some hoses and when I pulled that plug, pshhhttttttttt....air. And it had been sitting for several days too. So my axle is clearly building up pressure even after some normal driving, and two, it must be sealed pretty damn good because it's holding good pressure for daayyyyssssss. I figure it's a matter of time before it starts puking, so I'm putting in a catch can system and be done with it.

Random thought though - that axle isn't supposed to have some pressure is it? I wouldn't think so, but not sure. Or does the factory little vent think only release pressure above a certain value?

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I think it's just a rattle cap. So basically any small amount of pressure should open it. In fact, I'd guess that air can seep through it even when it's closed. I was pondering if yours could be sucking instead of blowing, but I thought if it's building up any kind of pressure it's probably positive. But under normal operation, you would want air to be able to come back in as it cools otherwise it'd gradually build up negative pressure so... Yours must be gooped closed I'd guess. Try shaking the valve (it should rattle) or blowing through it with your mouth.

BackInBlack said:

I think it's just a rattle cap. So basically any small amount of pressure should open it. In fact, I'd guess that air can seep through it even when it's closed. I was pondering if yours could be sucking instead of blowing, but I thought if it's building up any kind of pressure it's probably positive. But under normal operation, you would want air to be able to come back in as it cools otherwise it'd gradually build up negative pressure so... Yours must be gooped closed I'd guess. Try shaking the valve (it should rattle) or blowing through it with your mouth.

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Yup, the little cap rattles. Shouldn't be gummed up, it's a brand new car. There's no dirt, grease, nor anything else built up around it. Not a huge deal as my catch can/vent will be on mid week. Just added more for the discussion. Just weird it held pressure like that.

If you take the little metal cap off, there is a spring and a flapper valve there. The flapper technically will create negative pressure. On my last car, I ran a Bobs tank and removed the little flapper when mounting the metal capped piece to the tank. Free breathing solved the problem.

My new car has a Cortex vent in the cabin, since the car isn’t street legal anyway.