Thread: jag ind rear breather problems

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hi guys
on first long trip in model a we ran into a major problem with the diff blowing most of the oil out the breather pipe in the Mr Roadster jag quickchange cover.prior to leaving i had noticed it was doing ita little bit an moved the hose back to the rear most hole in the cover.both holes have baffles welded over them but obviously there is alot of oil movement inside that smooth cover an its getting under the baffles.
any ideas/help much appreciated.
mark


you can see the original breather hole at the front

What's the routing on your hose?

when the problem is sorted it will go up an onto the fitting you can see threaded into the centre of the crossmember that holds the jag diff head. at the moment it is looped up over the square crossmember above the chrome spreader bar an cabletied to it with a rag cable tied over the end

I'm no expert on differential vents, but just looking at the placement and thinking about the dynamics it appears that the top of the cover where you have the vent fitting is going to be seeing a direct shot of gear lube slinging off of the ring gear as it spins. Comparing it to my 9" Ford, my vent is on the driver's side axle tube, about three or four inches out from the differential housing, and it's a simple lightly spring loaded cap with no tube at all, and it blows no oil. Can you move the vent out of the path of the oil sling?

My thought is its heating up the air is expanding and pushing it (the vapors) out the tubes ..Is there any way to have bigger tube so liquid can run back down with out being pushed out???

if you look at the 2nd picture ,the little green plug is where i originally had it and it is in approx the same position as the oriiginal jag cover, just a little higher. the original jag rear breathe was a plastic tube that came out of the cover just above the oil level an went up about 4" an had a plastic cap on a spring- i'll find a picture of one

My opinion is that you need to cover the top of your baffle completely, the bottom needs to have the smallest of openings so that pressure can escape but fluid is blocked and if any fluid does get into your baffle your opening will allow it to drain.

Seems to me that the little green plug would be a better location, out of the direct sling path off of the ring gear, but I could be all wet.

Certainly not an expert on differential vents here either bit is seems to me that getting the vent high with a long hose may help this problem. Speedway has a kit - New Longacre 1 1 2" Clamp on Billet Rear End Breather Vent Kit w Hose | eBay but you could duplicate this with a nice stainless hose and a billet vent cap mounted as high as possible allowing the oil vapor to escape the rear end but cool and return as well.

the problem i've got is there is not much room under there to gain height and up into the mudguards isn't an option.the green plug is where i first started off with the breather and i'm thinking of playing around with the baffle there and going back to that spot as roger says-it seem to be the most logical spot.another thing is with the extra space in the quicke cover-theres an awful lot of oil in there compared to standard-wonder if i can run less??

You have to maintain lube [U]level[U] Don't use less and risk bearing failure

I agree 100% with Charlie, your fluid quantity is spec'd to give a specific coverage of bearings and you don't want to run lower. Just thinking, what if you came off of that green plug with a thread to compression fitting and took a three or four feet of 1/4"/6mm copper tube coiled in a tight spiral maybe 3" to 4" diameter ending with the tube coming back to center and turning up. Another tube fitting with a cap that has a nominal 1/16" or 3/32" hole drilled in the center? (fitting, tube bent straight up and coiled ending pointing up w/fitting - each turn on a 4" circle will eat a foot of tube) If it works you could replicate the whole thing in highly polished stainless to match the other bling, or just polish the copper & brass and clear coat it! By pointing up the coil would be self draining back into the diff, and there would have to be enough pressure to push oil up through the whole tube to get out. It would add an interesting "look" if done neatly. Just a thought....

Sandwitch a stock Jag cover between the rear housing and this quick change look a like piece---you can probably then just use the space in this Bling as a breather and leave the top with a tiny hole by drilling holes thru the Jag cover at bottom (for drainback) and in some other places for ventability--------

Originally Posted by jerry clayton

Sandwitch a stock Jag cover between the rear housing and this quick change look a like piece---you can probably then just use the space in this Bling as a breather and leave the top with a tiny hole by drilling holes thru the Jag cover at bottom (for drainback) and in some other places for ventability--------

I'd be afraid that I'd never really know where my lube level was running, as the space between the two covers would tend to fill with gear lube. Any hole at the bottom of the stock cover would cause the fluid to seek a common (low) level in both covers over time, not drain back into the main housing. I don't see two covers being the answer, and think it would be a second leak source. Just my $0.02.

Roger ( and others)


The whole porpuse of a breather is to somehow separate oil out of an oily vapor mix and return the oil liquid to the sourse while venting the vapor PRESSURE to the atmosphere--it is also necessary to somehow relieve an negative pressure in between these positive moments---


Now---with a plate (stock cover) between the housing and the Bing, it is only necessary to put a drainback (hole at bottom) and some other holes somewhere up above the liquid level and out of direct sling off area of the fluid--that will creat the separator and it only has to be vented to atmosphere by what could be a single hole as small as 1/16 to 1/8 inch---


And the fluid level will maintain itself at the filled level minus only the small portion that will be separated in the breather (volumne of cover to bling