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Kirkham Motorsports

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Old 03-01-2021, 02:04 PM
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Default Differential Breather

Hello all.
A little help. I was leaking rear end oil from my differential breather last month. The breather was a small pop up type cap. While driving, especially at freeway speed, oil was being pulled from it and leaking, not only leaving a mild spray across the lower half of the trunk but also leaving between quarter and half dollar size puddles in my driveway after stopping. I removed the pop up and installed a remote oil breather/oil catch can, positioned about 12 inches above the differential. It seemed to work until yesterday. The oil breather/catch can started leaking leaving the same size puddles in my driveway. I pulled the catch can off and it filled with about 3-4 oz of diff fluid. There are no other leaks other than from the catch can unit.

I am thinking the new breather unit is possibly siphoning oil from the differential. Anyone have similar problems or maybe a different reason why this is occurring and maybe a better solution?

When I filled the differential, I topped at the fill plug hole which Is about halfway up the rear ended. The differential is a Ford 9 inch with posi.

Thanks for any input.

John
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Old 03-01-2021, 03:13 PM
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you may be putting too much oil in the diff...
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Old 03-01-2021, 03:27 PM
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Where is the breather in relation to the oil level?

And in relation to the crownwheel?
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Old 03-01-2021, 04:20 PM
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Oil over fill was another thought I had. But the fill level was recommended to be at or just below the oil fill hole and that’s where I stopped. There is no loud gear whine or smell of burnt oil and the oil itself is still clean.

The new oil breather is bolted to the front outer trunk wall about 12 inches above the top of the differential itself.
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Old 03-01-2021, 04:26 PM
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If the crownwheel is splashing oil up to the FITTING on the diff housing, it will pump oil up a tube as the pressure increases from temperature.

So whereabouts on the diff housing is the breather fitting?
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Old 03-01-2021, 04:29 PM
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Here is the unit out of the car. Hose from diff goes to the “in” nipple. The “out” nipple is blocked off.

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Old 03-01-2021, 04:32 PM
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The original pop up breather was on top of the diff on the drivers side. A hose now runs from that location up to the new breather unit.
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Old 03-01-2021, 05:58 PM
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Quote:
Originally Posted by John248 View Post
The original pop up breather was on top of the diff on the drivers side. A hose now runs from that location up to the new breather unit.
So is that fitting on the diff centre, or an axle tube?
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Old 03-01-2021, 06:54 PM
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Quote:
Originally Posted by Gaz64 View Post
If the crownwheel is splashing oil up to the FITTING on the diff housing, it will pump oil up a tube as the pressure increases from temperature ...
This ^

Inadequate cooling along with internal oil splash is frequently the culprit. A flexible hose to an overflow / expansion tank will fix your problem without going to the expense of an oil cooler for the diff.

That said if the internal temps are getting high enough to force this leakage problem, it could be to your advantage to use an oil cooler for the diff.


Ed
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Old 03-01-2021, 06:57 PM
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It’s on the center section of the diff. Drivers side half way between the top of the diff and the axel tube.
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Old 03-01-2021, 07:12 PM
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Ok....
I have completely disassembled the breather unit. Cleaned it out and resealed all the fittings, added new hose, new clamps, new fitting on the differential and reinstalled the unit. I will take it out for a test drive tomorrow and see what happens.

I’m hoping that it is just an overfill issue combined with leaky connections. If it continues, I will look into the overheat issue and search out a good oil cooler. Just in case.....any recommendations?

Thank you all for the help.....and please don’t stop giving me advice. I am open to any and all suggestions.

John
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Old 03-01-2021, 07:19 PM
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I may be wrong but I have had detailed conversations with David Kirkham on this topic.you may also want to chat with morris on this site. But... You are using a catch can, when the oil goes into the catch can it stays there until it gets drained. I am using a reservoir and all the kirkham cars as well. when the oil goes in the reservoir it will drain back when you stop. see photo, also be careful not to add too much oil to the diff.
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Old 03-01-2021, 08:06 PM
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ERA626
I like setup you have. My catch can doesn’t recycle the oil back....it just catches it. I may go with your style setup if my problem continues. Thank you.
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Old 03-01-2021, 08:49 PM
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Ok....I think I’m experiencing a “hey dumbass” moment. When I filled the rear end with fluid I used the fill hole on the rear of the differential. Apparently the proper fill hole in on the carrier unit on the front of the diff. I noticed the rear hole is about an inch and a half or so higher up than the carrier hole. That being the case....Did I overfill the differential and now the “extra” is being pushed out ? ��
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Old 03-01-2021, 09:23 PM
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Quote:
Originally Posted by John248 View Post
Ok....I think I’m experiencing a “hey dumbass” moment. When I filled the rear end with fluid I used the fill hole on the rear of the differential. Apparently the proper fill hole in on the carrier unit on the front of the diff. I noticed the rear hole is about an inch and a half or so higher up than the carrier hole. That being the case....Did I overfill the differential and now the “extra” is being pushed out ? ��
I'd say that's definitely a possibility. Those fill holes are set not only to ensure adequate lubrication, but also leave sufficient space to allow for expansion. Obviously filling to that higher hole would reduce room for expansion and, voila, puke city.
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Old 03-01-2021, 09:36 PM
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Thanks Brian for the confirmation. I was sitting in the garage going through my build pics looking for clues to issue when I noticed the two different holes. I had completely forgot about the lower fill hole. I put a note on the diff to remind to add oil before driving, and that note was near the top hole.....so that’s where the oil went. Like I said....”dumbass moment”. But hey...I least I put oil in it !!!

John
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Old 03-02-2021, 03:48 AM
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John,

We all have had those "dumbass" moments. Anyone that says that they have not just doesn't realize that they did. Good luck. I too have a differential oil catch can that feeds in from the bottom as we'll.

Jim
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Old 03-02-2021, 07:14 AM
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Mine feeds to trunk, simple $15 jaguar unit.
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Old 03-02-2021, 08:30 AM
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Quote:
Originally Posted by John248 View Post
Ok....I think I’m experiencing a “hey dumbass” moment. When I filled the rear end with fluid I used the fill hole on the rear of the differential. Apparently the proper fill hole in on the carrier unit on the front of the diff. I noticed the rear hole is about an inch and a half or so higher up than the carrier hole. That being the case....Did I overfill the differential and now the “extra” is being pushed out ? ��
bingo
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Old 03-06-2021, 10:15 PM
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The correct oil fill level is from the front side of the center section with the plug just behind the pinion bearing. The fluid should be no higher than the bottom of the hole. It sounds like you were overfilled.

You also need an overflow that will drain back down into the differential. Once you get these two accomplished you should be good to go.

Tom
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