Oil patch below Diff

[robo1968]

Cars been sitting for about 3 weeks now in the same place and I was inspecting underneath - there's a few drops of oil on the ground below the diff on the near side about where the prop shaft comes out.

Should I be worried?

[a4gom]

I wouldn't, just keep an eye on the level. Mine did it from the pinion seal took it all out and got the seal replaced it was fine, just had it out and in bits to change the ratio and it's leaking again even though we used a new seal. Big job for little return IMHO

[John Loudon - Sponsorship Liaison]

Ditto above. Also worth noting that with old high milage parts, the shafts that the seals fit against may now be worn and undersize so new seals "may" not fix the issue

[SteveD]

Cars been sitting for about 3 weeks now in the same place and I was inspecting underneath - there's a few drops of oil on the ground below the diff on the near side about where the prop shaft comes out.

Should I be worried?

i would be worried ,very worried , if my propshaft came out of the n/s of the diff

seriously as above

[robo1968]

It's not a high mileage car so I'm guessing it's the seal. I will post some pictures later and see what you guys think. How do I check the oil level? Open the filler nut and the level be up to that?

[robo1968]

How much oil do diffs usually need? If I remove the filler nut should the oil level come up to that plug?

[rocket_rabbit]

Yes. On all the diffs i've done, no more than a litre.

[Hammy]

All of the above plus also just worth checking there is no up/down movement of the shaft as this would indicate a bearing problem  which would wear the seal more rapidly . Then it up to you whether to change it or not .  Give it a wipe down to be sure the leak isn't from the cover gasket .

[robo1968]

Quick update - I've found the culprit and I have to admit now feeling stupid for not thinking about it before   (at least I'm learning though!). The oil catch tank for engine breathing has a pipe that goes to the rear and exits just to the nearside of the diff (makes the catch tank auto empty whilst driving as air rushes past end of pipe) - and that's where the oil was - directly beneath it! I was just a bit paranoid that it must have been something bad like the diff leaking. Must have come out soon after I last parked the car in the garage but only noticed it when I took the boot box out 3 weeks later. I was however only looking from the top so didn't notice the pipe until I got underneath it today. Pic below:-

[SteveD]

call me dumb but what is the point in having a catch tank if it dumps oil out automatically on the road or track ,bit bleedin stoopid if you ask me and pointless having a catch tank

[robo1968]

I don't really know but I don't think it's completely pointless as I think the idea is simply to draw the fumes off the engine. The amount would be tiny and wouln't normally be dumped in the road but dispersed in the air in a fine mist. Anyway, in the builder's own words:-

"There are two 1 litre catch tanks. One takes oil fumes from the engine block and the other takes oil fumes from the cam cover. Each tank has extract pipes leading underneath the into the air stream. The idea is (like a spray gun) that air moving underneath the car when it is moving will cause a depression in each tank and hence draw fumes off the engine."

[SteveD]

should really have a small air filter type set up on the catch tank/tanks to stop anything coming out at all

[robo1968]

Quick update - I was completely wrong above about what the tube is that exits down beside the diff - it actually comes direct from the diff. I just didn't bother to follow the tube and presumed it was for something else. I didn't realise that the diff would have a breather tube? Why does it have one and is it fairly normal for a few drops to emerge after parking it up?

[SteveD]

it has to breath , just put a little resovoir on the end of the pipe like a plastic motorbike front brake resovoir above the diff ,then if any oil comes out it will drain back in

[robo1968]

Thanks ok. At the moment it runs around bulkhead then exits downwards under car (as in pic above). Do you think I should cut it short and have short tube of a few inches with resovoir on top?