Thread: jag ind rear breather problems

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I just wrote a lengthy post explaining this from the very simplist basic views to the upward levels of a nascar/F1 version of fluid/vapor controls and it wouldn't post-----so much for me on this post

Originally Posted by jerry clayton

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

Jerry, I mis-understood what you were saying about the way the two covers would work, and it seemed to me that you were suggesting that the void between the two would remain empty, there only for a vent area. Obviously that's not what you meant.

I would suggest that if you used both covers you would want several large holes at the bottom, or even a significant portion of the stock cover cut away so that the lube level would equalize quickly during fill. A small hole at the top, and equally a small vent in the "quick change" cover would handle the venting both ways, out and in. The only concern would be getting the outside flange of the stock cover smooth and flat to seal to the "quick change" cover.

But I think I'd try the vertical coil of tubing first......

Roger--the only problem with usinf a coil of small diameter tubing is that the smaller the tubing, the further it squirts----needs to be larger to allow liquid and bubbles to separate and drain back because of gravity--


Problem with the set up as Sharpmark has it is that the sling off from gear will constantly be going in that direction and going out---
With the OEM rears where it is on top over the axle tube---that is a high vlume area of probably 3 " tube for separation and drain back with small hole to relieve pressure adequately to prevent blowing past the axle seals---------


On hotrods, people really need to copy what the oem manufacturers have done--if it works on millions of daily driver/work vehicles, it will probably work on a trailer queem

Yeah, that's a good point on the tube size, and bigger than 1/4" would be better. On the sling, that's why I suggested using the other hole, currently identified by the green headed bolt. I'd probably start with the 1/4" in the OEM location, and if it didn't work boost it to 3/8" or so. Away from the sling forces the little tube just might work, and a few feet of copper tube isn't that expensive!

Many off road racers and others who work their off road trucks use "catch cans" on their diff and transfer case breathers. They are actually small expansion cans very similar to the ones used on radiators, with a fitting inlet connected to a tube that reaches to within a fraction of an inch of the bottom of the can, and a filtered vent fitting on the top of the can. Any oil that gets caught in the can and reaches above the level of the bottom of the tube gets pulled back into the diff as the cooling draws air back in through the filtered vent. However, in your situation, one or another of the fixes already put forth should work quite nicely; my suggestion is just another bit of fodder to toss in the idea mixer.

thanks for all the replys.i did consider the original rear cover sandwich but i would'ht have put any holes in it -- just left the original breather on it and left one of the plugs out of the quickie to let the air out.on an original jag i drove there was never any oil coming out of the original breather.the problem is i don't have an original cover only photos!!!i'm going to change the shape of the baffle over the front breather and increase the diameter of the breather hose and put some anti-foaming in and see what happens.
next option will be the coil idea.
once again thanks everyone for the interest in my problem- i'll keep you all informed.

problem solved-thanks for all the input.
what i did was plug the rear breather hole and weld completely round the baffleplate closest to the diffhead and then drill 2 small holes in it top and bottom.
i also drilled and tapped the breather hole to 1/2"bsp and used a larger diameter hose.i used a length of hose with a horizontal loop in it and cabletied it to the pickup floor crossmember temporarily.
went on a 400mile trip an not a drop of oil came out so will now replace the temp hose with a blingy piece.
once again thanks everyone.

So that's why I never saw you or the truck after Friday!
You went home!