In short:

Replaced O/S driveshaft, discovered gearbox oil all over bottom of engine, rear torque mount and up the back of the engine, seems its being flung around by the driveshaft, replaced shaft seal, pressed in new seal further than old one as I thought i'd pulled it out a bit with the old drive shaft removal, turns out this is wrong and the old seal was seated correctly, driveshaft I installed is 906mm in length, i'm seeing others 904mm or 899mm. Could the leak be caused by incorrect driveshaft length and not being fully seated in the gearbox?

 

I installed GSP Driveshafts a few months ago. Looking under the car recently I noticed a small drop of oil forming from where the gearbox meets the engine, I thought maybe the engine sump gasket had failed since it looked a bit crusty. I couldn't figure out whether the oil was gearbox or engine since there was so little of it to smell. Drove a couple thousand miles, did some other work and took the car for alignment, they didnt mention anything, but had to take it back to them as the steering wheel wasn't straight. They then pointed out to me that the sump and gearbox were drenched in gearbox oil.

I had a look, i thought maybe a driveshaft seal had failed. Looking at it, the wet side is the driver side (longer) drivershaft, I can't really see if its coming from the shaft seal. There is gearbox oil on the rear torque engine mount and up the back of the engine block directly above where the driveshaft goes into the gearbox, also all over where the gearbox bell housing meets the engine block so I assume this oil is being flung around once it leaks. I popped the shaft back out, at first I thought maybe I had pulled the seal forwards out of the gearbox when pulling the old driveshaft out, so I pressed a new seal in which went in further than the old one. I thought this would fix the problem. Noticed today after a motorway drive, the bottom of the engine is drenched in oil again in the same way. Looking online, the seal is supposed to sit flush with the flange and not to be pressed in further (which is my mistake) but this raises the question, Was the seal bad in the first place?

The length of the driveshaft I bought was listed at 906mm, however i'm now noticing lengths of 904mm and 899mm. Could this oil be leaking out of the driveshaft seal because the drive shaft I bought is the wrong length or would these lengths not make a difference? They're all listed as suitable for my vehicle.

As nothing has been posted yet, I'd say the source of the leak needs to be confirmed so clean off everything and find out exactly what the source is.
Do you now have 2 seals in place or did you take one out?
Agree the seal should sit flush and bear on a very smooth section of the driveshaft section that goes through the seal.
If it doesn't do that then the lip will be damaged.
If it's that bad, there's something seriously wrong - is the oil level above the level of the seal, if that can be observed?

Need to check the exact part is suitable for your VIN?

On 10/24/2025 at 10:33 AM, Shearers said:

As nothing has been posted yet, I'd say the source of the leak needs to be confirmed so clean off everything and find out exactly what the source is.
Do you now have 2 seals in place or did you take one out?
Agree the seal should sit flush and bear on a very smooth section of the driveshaft section that goes through the seal.
If it doesn't do that then the lip will be damaged.
If it's that bad, there's something seriously wrong - is the oil level above the level of the seal, if that can be observed?

Need to check the exact part is suitable for your VIN?

I have now taken the new seal out and refitted, oil level is correct, the leak now doesn't seem to be coming from the drive shaft seal. I can't really determine where it's coming from but I do have a couple pics after a motorway drive. It may be something internal.

I can't see any "massive" leaks and the only thing that sprang to mind was that it may be coming from that cable which I suspect may be the reversing light switch, or the oil pressure sensor (I don't know that engine so really difficult for me)  if that's what it is OR...?

1 hour ago, Shearers said:

I can't see any "massive" leaks and the only thing that sprang to mind was that it may be coming from that cable which I suspect may be the reversing light switch, or the oil pressure sensor (I don't know that engine so really difficult for me)  if that's what it is OR...?

Its definitely gearbox oil as the engine oil level has not dropped since I changed it last month, I do believe ehe reverse light switch is on the right of that pic away from the wet area, not too sure what that connector is for.

Here is a video of the leak currently, I cannot pin point where its coming from.

 

 

That leak is on the engine side.  It does look like engine oil to me...unless the clutch is spraying gearbox oil all around the bell housing from an input shaft leak.

That connector is the for crankshaft sensor.  It's just picking up from the flywheel.  There's shouldn't be any oil under it.

35 minutes ago, TomsFocus said:

That leak is on the engine side.  It does look like engine oil to me...unless the clutch is spraying gearbox oil all around the bell housing from an input shaft leak.

That connector is the for crankshaft sensor.  It's just picking up from the flywheel.  There's shouldn't be any oil under it.

That's the thing though, I haven't noticed a drop in engine oil, and it doesn't really smell of anything, I've noticed if you look at the top of the bell housing under the intake manifold, it looks wet there to. 

22 minutes ago, Lochlan said:

That's the thing though, I haven't noticed a drop in engine oil, and it doesn't really smell of anything, I've noticed if you look at the top of the bell housing under the intake manifold, it looks wet there to. 

The engine oil sump is really wide.  You won't notice the level drop on the dipstick until at least half a litre has gone.  There's barely anything dripped there so far.

If it doesn't smell of anything then it's not gearbox oil.  That smells horrible.

The alternative for a leak within the bellhousing would be the crankshaft seal.  And the back of the flywheel would spray that leak all around the join between engine and gearbox.  That would also end up around the crank sensor.

Looks like we are getting closer now that potential sources and connectors are clarified, Thanks!...

1 hour ago, TomsFocus said:

The engine oil sump is really wide.  You won't notice the level drop on the dipstick until at least half a litre has gone.  There's barely anything dripped there so far.

If it doesn't smell of anything then it's not gearbox oil.  That smells horrible.

The alternative for a leak within the bellhousing would be the crankshaft seal.  And the back of the flywheel would spray that leak all around the join between engine and gearbox.  That would also end up around the crank sensor.

 

I don't think it's engine oil, I understand what you're saying, but the consistency is more like gearbox oil, and appears to be coming from the gearbox side, I had to fill the gearbox up with alot more oil that came out of it when changing the driveshaft seal so that probably wasn't the solution to the problem. As for the smell, After popping my head right under the engine it does smell a bit like gearbox oil, and when driving I sometimes get a smell of burning gearbox oil, not engine oil. I'm really starting to think it's gearbox oil making its way passed the release bearing.

1 hour ago, Lochlan said:

I'm really starting to think it's gearbox oil making its way passed the release bearing.

At this point I'm not sure it matters too much.  Sounds like it'll need gearbox off either way.

The final check would just be to make sure it's not leaking from the vent on top of the box.

2 hours ago, TomsFocus said:

At this point I'm not sure it matters too much.  Sounds like it'll need gearbox off either way.

The final check would just be to make sure it's not leaking from the vent on top of the box.

Where abouts is the vent on the box? I can't see much from the top of the engine

3 minutes ago, Lochlan said:

Where abouts is the vent on the box? I can't see much from the top of the engine

It is right on top of gearbox.  In the central section (not bellhousing and not under battery).  Should be able to see it from above around the air intake.  Might be worth trying a mirror in a stick if you've got one.

On 10/26/2025 at 11:05 AM, Lochlan said:

 

I don't think it's engine oil, I understand what you're saying, but the consistency is more like gearbox oil, and appears to be coming from the gearbox side, I had to fill the gearbox up with alot more oil that came out of it when changing the driveshaft seal so that probably wasn't the solution to the problem. As for the smell, After popping my head right under the engine it does smell a bit like gearbox oil, and when driving I sometimes get a smell of burning gearbox oil, not engine oil. I'm really starting to think it's gearbox oil making its way passed the release bearing.

 

Just want to give an update on this, i've been monitoring the leak for a couple weeks now. Originally I couldn't pin point whether it was gearbox oil or engine oil. I'm now leaning towards it being engine oil despite what I said. Having compared both engine and gearbox oil and finally being able to smell whats dripping I'm gonna change my assumption to engine oil. I just cannot find where its coming from, and also the engine oil level does not drop but oil still coveres the bottom of the engine and gearbox.

A little oil can look like a lot and I'll say the immortal words,... what about trying some stop leak (it's a bit Marmite and not for use on wet belts!)