F13 Breather Thread

[steg1970]

I've had problems with the gearbox presurising and blowing oil past the seals on the shafts. I am going to increase the size of the breather and install an overflow bottle, for this I need the thread size on the breather which sits on top of the turret, I'm guessing its a UNF thread can anyone confirm this or tell me something different.

Ta

[mowgli]

right, it sounds like you have got the cap pushed down on the breather top.. cos they are usually pushed down & need lifting up with a screwdriver.

also, are you sure it was left to settle for a good long time before checking the oil level plug, cos 80-90 gear oil has a habit of binding to gears & bearings, an thus will give a false reading if checked too quickly after its been run.

the box is metric, but someof the threads are a bit weird

[steg1970]

The gearbox is a Quaife SC/CR Synchro with a SC 4.86 final Drive, it uses Millers NT oil.

First thing I did was make sure the cap was nice and loose. Then I took out the breather and cut the bottom off and drilled it out to 6.5 mm, which improved things but didn't cure the blow past. also running the box with slightly less oil as per advice from other rallyists improved a bit further.

There is no more meat to cut out of the breather plug so I am going to replace it, I might end up modifying the turret and re drilling/threading that.

[garyc]

What I have seen before is the breather bolt opened up and something like a brake cylinder resevior screwed in there. Are you blowing oil out the top of the breather too?

[mowgli]

i still don't see how it is producing so much pressure, unless the sc gears are throwing the oil up & it is gunning the breather up, maybe try placing a small baffle plate underneath it

[steg1970]

I spoke to a transmission specialist at M-Sport who said hes seen this to a greater or lesser degree with straight cut gears, apparently a straight cut gear will thrash the oil to a foam and bubble up inside the box.

Some oil has come up the breather but mostly blows past the driveshaft seals. Its alot better now than it was but still weeps past and dripps onto the sump guard. On the 2010 Pendragon (the first rally with the new box) I used over a litre of oil!!

[autoworksnovasport]

isnt there a different oil you can use??

[steg1970]

I used to use Castrol B373, but that was the same.

[mowgli]

how old are the 1/2 shaft seals?

is it time to fit a pump & oil cooler?

[pottersrebel]

can u not run automatic transmission fluid? i was lead to believe it was thinner than normal gear oil? thats what i run in my stockcar box and that spends all day in second gear without a problem

[mowgli]

and stock cars run short, furious races lasting a few minutes before stopping....

[pottersrebel]

was just a thought? it works for us guys

[steg1970]

Its had several sets of shaft seals (and different shafts too) with no improvement.

I have to use an oil that will provide shock protection to the plates and clutches in the ZF diff.

Seriously guys I've gone through this for 18 months, can someone just tell me the thread size of the breather please.

Ta

[boffer8]

Hi, one of the easiest ways to fit a breather is to take off the turret and then drill and tap it for a fuel push on fitting thread size (in various metric and imperial fittings to suit your own requirements often used on facet fuel pumps) so you can use a simple bit of 8/6mm hose to a breather pot. seen it done on a few Vauxhall rally cars now, makes for easier topping up too.

[crash_ndie]

^^^^ as the man says its easyer just to drill and tap it your self you i used a threaded air line hose and just push the tube over the end and ran it to a catch tank mounted on the inner wing worked a treat

[steg1970]

Thanks guys I'll try that.

[joshy]

can you not drill and tap some other sturdy part of the casing?

[ollysport2011]

Alrite pal, I wudnt be drilling holes that arnt suppose to be there. It produces a weak area, and the amount of stress going through the turret could easily lead to a failure. Try running less box oil. Or on ur nxt event let it chuck out what it doesn't want, and not top it up. In my f20 dog I'm supposed to run 2ltr, but I only use 1.75 ltr. And in over 30 events I havnt had a problem. Hope this helps mate