BACK AXLE

[robert mackay]

Hi there. I was looking for feedback from members on the advantages of venting the back axle. By installing a vent pipe on the top of the diff will this help relieve presure on the seals.

[Alastair Gregg]

Hello Robert,

I don't feel qualified to confirm or otherwise the benefits of the modification you suggest. What I do know is that that axle is pretty nearly bomb proof, it was used on some much higher powered Jaguars and the Triumph TR2 (A?). When chatting to folks I have never heard of anyone saying, "ah the seals went on the back axle" Now watch them all crawl out of the woodwork telling us just how wrong I am

What sort of a vent (non return I hope) had you in mind?

[Forumadmin]

The axle does have a vent for grease near each hub. Whether this also acts as a vent for the diff casing I do not know. Clearly a vent must allow air and hence muck in unless it has a filter. I would imagine the leather front pinion seal has some degree of air seepage past it anyway. Leather breathes!

[vicboddy]

THere is already a vent hole which allows the diff to breath. It is situated on the RHS diff tube, seen from the back, about two inches from the weld to the diff carrier/casing itself, in the horizontal position. It is a hole similar to the two holes which allow excess grease to escape from the hub bearings, ie it is a drilling of about 1/8 inch. I suspect many people do not realise it is there, and that it has become blocked with grease and/or painted closed. BUt I suspect that if blocked, pressure will build up as the diff warms up and oil will leak out somewhere. When I stripped the brakes on SC990 one side was indeed full of diff oil (not grease) and when I checked, this breather hole was blocked solid.

By the way, I have just checked the three Jupiter diffs and two JAvelin diffs I have and each has this drilling.

If your plan is to increase the size of this drilling, and to tap it to suit a vent breather which will stop water or worse getting back into the diff as it cools, I think that sounds very wise. Regards vic

[robert mackay]

Thanks for replys. After cleaning and closer inspection i did indeed find the vent hole that vic spoke of which was totally blocked. I suppose this small 7/64'' dia hole is quite adequate if kept clear but i think i may still do my own modification in the way of a vent pipe.