Kirkham rear differential query

[Dimis]

I was installing the diff yesterday, when I notice what looked like two vents on the Kirkham Auburn 3.42 rear diff.

The first comes out of the upper body of the diff housing with the rubber tube coming out of it. This I assume is the primary differential vent. Which I connected to the breather that is mounted in the boot (rear trunk).
Later when I was cleaning up I remembered that I had retrospectively ordered Kirkham's upgraded diff vent, which has stainless steel lines... I'll have to go back & swap out the rubber one

The second, just above the filler bolt on the rear punkin casing... has me a little confused... what is it & what is it for? what do I need to do with it?



I'm assuming it should be plugged or also vented to a breather otherwise wont it splash grease & oil everywhere under some spirited driving as things heat up?

[mickmate]

You're right it is another breather, it could be tee'd into your other breather line and routed up to the breather can. Duh I didn't look closely at your picture and read your question.

[cobrakiwi]

That is the original breather location, on my 2 Kirkhams I have one with the breather coming out at that location and one with the breather coming out on top of the diff housing, I would just plug the one on the cover.
A quick call to Kirkham would put your mind at rest.

[4pipes]

That location may be for the coolant return if you use a differential cooler.

[Morris]

You might want to make some modifications to the rear end cover to be able to do some Oval or Road Course driving......

This set up has been tested under the most sever conditions....

[fordracing65]

I didnt even see these upgrades on any option list, is there something i am missing, I have a Kirkham on the way.

[Avmaviator]

Originally Posted by fordracing65

I didnt even see these upgrades on any option list, is there something i am missing, I have a Kirkham on the way.

I didn't either Pete.

It must be a special option so the cars can run upside down other there, or if you run over a kangaroo your diff will still be well vented

Dimis, I don't have that vent on our cover.

[fordracing65]

I think he has an older diff, he has a 3:42 ratio, mine is a 3:55, and at the open house all the lines pretty much are now steel braided where need be, and the aluminum diff is standard now.

[patty442]

The line attached to the top of the differntial housing is not a breather. It is a return line from the differential cooler, which sprays specifically the pinion bearings with cooled differential lubricant. The exact location in your photo is a little off from oringinal but it will get the job done. Not sure what Kirkham guys think it should be but I have 6 original cast iron 427 competition diffentials, every ratio, which all have the a fitting tapped into the exact same spot on the upper portion of the cast iron Salisbury case above the pinion bearings. No need for shoulda, coulda, woulda, I assume, etc. discussion. That's what it is.

[dcdoug]

Originally Posted by Dimis

I was installing the diff yesterday, when I notice what looked like two vents on the Kirkham Auburn 3.42 rear diff.

The first comes out of the upper body of the diff housing with the rubber tube coming out of it. This I assume is the primary differential vent. Which I connected to the breather that is mounted in the boot (rear trunk).
Later when I was cleaning up I remembered that I had retrospectively ordered Kirkham's upgraded diff vent, which has stainless steel lines... I'll have to go back & swap out the rubber one

The second, just above the filler bolt on the rear punkin casing... has me a little confused... what is it & what is it for? what do I need to do with it?



I'm assuming it should be plugged or also vented to a breather otherwise wont it splash grease & oil everywhere under some spirited driving as things heat up?

My understanding is that the port on top of the diff is for an diff cooler and should be blocked off if you aren't planning to run one.

The primary vent is the one that comes off of the pumpkin cover and probably has some mesh, etc on the inside to keep fluid from splashing out of the vent.

Can anyone confirm which is right?

EDIT: By the way, Kirkham says to run 90w gear oil with no friction modifier.

[fordracing65]

Looks like you have a full out race car, very nice, me likey...

[Dimis]

Originally Posted by dcdoug

My understanding is that the port on top of the diff is for an diff cooler and should be blocked off if you aren't planning to run one.

The primary vent is the one that comes off of the pumpkin cover and probably has some mesh, etc on the inside to keep fluid from splashing out of the vent.

Can anyone confirm which is right?

EDIT: By the way, Kirkham says to run 90w gear oil with no friction modifier.

Thanks dcdoug,
Top vent has been plugged, and diff has been installed.

As for diff oil.... well, its a little contentious but...

From my notes as per Kirkham's old webpage:

WARNING: The differential covers that we use locate the drain plug approximately an inch higher. Do NOT fill the differential to the drain plug (Refer to the yellow marked line in my pic).

3.25 pints 85W90: GJ-6. Mobil + 4 oz Friction modifier.

For Auburn use Auburn part number: 504102
For Dana use Ford Friction modifier (ford part number M-195-46-A12) old petroleum based NOT Synthetic.



As per Morris's experience and testing - (I quote him from the notes I've taken). The oil that should be used is Mobil 1 75W140. This is the best oil we have tested and reduced our temp by 40-60*degrees. Way better then all other products

I haven't found anyone that imports the Mobil1 stuff here to Aus at a cost effective price, so I've opted to use Nulon 85W140, its an Aussie product that is the equal as the Mobil 1, as I've been advised.

Kind regards

[dcdoug]

Dimis, my bad. I forgot you had the Auburn diff, which I used to have and does require the friction modifier. I just upgraded to the Kirkham Eaton True Track rear which doesn't use friction modifier. Sorry for the confusion.