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.

[Avmaviator]

Originally Posted by 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.

When is yours coming in Pete?

[fordracing65]

Not sure have not got a car number yet, but im looking at December to have it on the road, the summer is here in AZ so its a no drive for sure for at least the next 5 months, unless I drive at night. lol, Its gonna be bad ass thats for sure, I got a few tricks up my sleeve, already named it Pride and Joy. Gonna do some drifting videos, as well as the mile all out run for top speed, even got a helicopter to shoot video for a short film for it. All in HD.

[Avmaviator]

Originally Posted by fordracing65

Not sure have not got a car number yet, but im looking at December to have it on the road, the summer is here in AZ so its a no drive for sure for at least the next 5 months, unless I drive at night. lol, Its gonna be bad ass thats for sure, I got a few tricks up my sleeve, already named it Pride and Joy. Gonna do some drifting videos, as well as the mile all out run for top speed, even got a helicopter to shoot video for a short film for it. All in HD.

Easy tiger!

[Dimis]

Thanks guys... I figured as much it being a breather... but what to do...?

Options:
1) Seal it off
2) Tee it in at the junction
3) Run 2nd separate breather

I'll mull on it.

Originally Posted by 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.

Correct & correct again. I believe all are now braided as standard so not an option they'd discuss with you.

Originally Posted by Avmaviator

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

Hopefully no Roos where I'm driving... mind you some have been trained to dodge the traffic
Kangaroo near miss : Bathurst 2007 - YouTube

Others not so well trained
bathurst kangaroo hit - YouTube

[Morris]

FYI ...... we run 3 different Kirkham Diff with Quaiffe Differential in all three ..... and they were notorious for puking oil out of them ...... some folks had issues just driving on the street.....

Many folks had a problem with the oil going up to the catch can .... and filling the catch can up from the rear end....... Also you should notice the line drawn on the steel cover ....that shows the kirkham cover fill hole is to high and over filling is what a lot of folks did..... The aluminum Jag cover shows the correct height the oil level should be.....

We built this mod on the steel covers and tested at Road America/St Louis International/Road Atlanta...... and did not puke any oil out and were able to control our rear end oil temp down to 280*degrees from 320*degrees...... and yes we run a oil cooler and fan on our rear end cooler.......

Morris

[Dimis]

Originally Posted by Morris

FYI ...... we run 3 different Kirkham Diff with Quaiffe Differential in all three ..... and they were notorious for puking oil out of them ...... some folks had issues just driving on the street.....

Many folks had a problem with the oil going up to the catch can .... and filling the catch can up from the rear end....... Also you should notice the line drawn on the steel cover ....that shows the kirkham cover fill hole is to high and over filling is what a lot of folks did..... The aluminum Jag cover shows the correct height the oil level should be.....

We built this mod on the steel covers and tested at Road America/St Louis International/Road Atlanta...... and did not puke any oil out and were able to control our rear end oil temp down to 280*degrees from 320*degrees...... and yes we run a oil cooler and fan on our rear end cooler.......

Morris

Thanks Morris,
Most informative, but this raises my curiosity, so if I may, a couple of questions.

1) How does your mod on the steel cover actually work? ie: the reasoning behind it?
Doesn't the oil still heat up & thus pressure formed & thus hot oil getting puked up the catch can? or does it act as a physical barrier preventing the hot viscous oil from splashing up?

2) I'm going to need to add an oil modifier into my diff (as advised by Kirkham), so what ratio of oil modifier to oil should one be using to prevent going above the "yellow line" and puking oil everywhere if a) on the street, b) club tracking this car (not on slicks... so temps not as high as yours)?

3) Did you have any problems with increased temps & pressures blowing out seals? or was the catch can sufficient in reliving the pressures? Reason for asking is because it will determine how I go about capping the 2nd breather.

[fordracing65]

Im so confused.

[Morris]

Dimis

Without this mod ..... the oil can be slung off of the ring gear and directly into the vent hole ..... which will continously pump oil out of the rear end.

So we have installed 3 each barriers..... one to separate the ring gear side from the differential side of the spinning carrier..... one to stop oil that is coming off of the differential carrier .... one over the actual vent hole that only allows air to pass on 2 sides......

The major fence is the large one that is dividing the ring gear and differential.... that keeps the majority of oil on the gear side.

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 of the other products.

I've enclosed a photo to show that the one vent line is on top and the other line is oil cooler back in to flow oil where the ring and pinion meet.

The catch can runs clean now and no pressure from heat or motion.

Morris

[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