Consequences of driving with a leaking rear differential?

[wax lyrical]

Guys, I'm just wondering what the consequences are of driving with a fairly serious rear differential oil leak? Would the differential fail 'progressively' or suddenly and what are the symptoms?

Car is a 2008 BMW 335i (auto), with 200k miles on the clock.

Many thanks

[ITwannabe]

Never had to but I wouldn’t be driving it more than a walking pace from my garage onto a trailer.

You’ll soon get a lot of heat in a small coupling, then the metals increase in size and you’ll either seize or explode I’d say

[Sheepshanks]

wax lyrical said:

Guys, I'm just wondering what the consequences are of driving with a fairly serious rear differential oil leak?

Riders falling off motorbikes.

[Whatapex]

Doesn't really matter does it ? I mean, surely you're more concerned with the slippery substance you're dumping if you were to drive it around ?

[Miserablegit]

Sheepshanks said:

Riders falling off motorbikes.

This +1 - please don’t

[mat205125]

Sheepshanks said:

Riders falling off motorbikes.

This!

Ultimately the consequences will be a big bill when the diff fails, and maybe a crash if it fails at speed and locks the axle

[campionissimo]

Having had a rear diff fail on a BMW 325i i wouldn't want to risk it at all. When they go, the bang will make you jump, and the lack of drive will happen at the most inconvenient moment. Not cheap to replace either.

Plus that thing about motorcyclists too........

[OutInTheShed]

It's probably been a minor leak for a long time, so the oil is mostly gone?

You don't want to be in a car where the wheels suddenly lock up on a corner.
I did that once, luckily doing about 20mph.

[wax lyrical]

Thanks Guys. I don't think it's been going on for a long time - car has full BMW main dealer service history and this problem was picked up for the first time as an 'advisory' after an MOT a few weeks ago (which was done by the BMW dealer).

[stevieturbo]

Why not just fix it ?

If something needs oil to survive...it tends to die without it. A bit like people and water...what would happen you if all you're water leaked out ? and was not replenished ? lol

[E-bmw]

stevieturbo said:

Why not just fix it ?

If something needs oil to survive...it tends to die without it. A bit like people and water...what would happen you if all you're water leaked out ? and was not replenished ? lol

^^^^ Wot 'e said.

Why wouldn't you?

[Pica-Pica]

By coincidence, my 335d is in today for a rear diff gasket replacement. It was ‘misting’ last December. They said bring it back after a couple of months, to re-check. They are replacing the gasket.

[shalmaneser]

To answer the op the bearings and gears will wear faster. This will lead to a whine from the diff which will get louder as the bearings get more and more worn. Eventually they will fail and likely lock up but the whining will be very loud by that point.

It's relatively easy to top up the fluid and the comments about bike riders falling off are a touch hysterical given the amount of diesel that I see spilt on Her Majesty's Highways 1.5 litres of diff oil would barely make a difference. Clearly if it's pissing out then that's a different matter but a drip here or there is not that concerning.

It's a fairly large job to replace the axle seals but the diff cover gasket can be replaced quite easily.

[DickyC]

Depends where it's leaking from. If it's the oil seals, oil will be retained beneath that level. If it's the drain plug, all the oil can escape. And so on. Find where it's leaking.

The seals on mine were leaking. The local transmission specialist fitted new ones for £600 or so. One seal was still dripping. Took it in yesterday and picked it up today with the leaking seal replaced again. No charge.

To pass the time I rang the main agent to enquire about a replacement diff. £3,300 plus fitting.

It's worth having it fixed.