What happens when a diff runs with no oil???

[Elmo]

Just wondering if i could get some advice and knowledge off some people who are actually in the know about what happens when you drive your car with no diff oil?

I was out wheeling all weekend, but on a night run on Saturday night i snapped the 2 lower most studs on my rear diff centre, losing all oil pretty much instantly. Unforutnaly i was on the crux of a decent climb and no main road anywhere nearby and had to drive myself out so as to enable the tow truck to get to me to get me home. But i ended up driving about 4 or 5 kilometres. I stayed in 4WD the whole way hoping the front would do some of the work, (if i had of disconnected the rear tailshaft i would not have got out) and i limited my speed to Idle in Low range 1st or 2nd gear the whole way in the hope of not getting too much heat build up, the speedo never left 0kph (it took 3hours to do that 4 or 5km).

Just wondering what i should be looking for upon teardown as i really dont think im going to be as lucky as replacing the 2 studs and re-filling with oil. Im thinking bearings will be shot given that they are so small and any drive without oil would have killed them, possible diff gear heat, anything else?

Any advice will be appreciated, i dont want to re-build only to have it explode or fail down the track, whether 10km or 10,000km, i want to fix it properly first time around...

Cheers in advance

[pcman]

5-10 kays there would be minimal damage especially at low speed

fix the studs wack in new oil, probabally drain the oil again after a few hundred kays incase theres some metal wear

[georgey]

hey rob.
Everything should be good mate.
Its at high speed with no oil that the diff starts to heat up and can explode.
There shouldnt be any real damage going slow for that amount of time.
I drove home on the rear with no oil but didnt care because i had a spare centre.
Pulled it out but wasnt damaged

[351ciofgrunt]

At walking speed there shouldn't be enough heat generated to cause damage, I'd say you should be allright.

[Tiny]

Over time you will stuff bearings and gears, at that speed and distance there was probably enough oil over thr wear surfaces that it's unlikely any damage occured

[chimpboy]

5-10 kays there would be minimal damage especially at low speed

fix the studs wack in new oil, probabally drain the oil again after a few hundred kays incase theres some metal wear

I would probably do the same.

[MrGrim]

add a tube of nulon g70 this stuff works great i did over 50ks with no oil in the diff was all good when i pulled it out put back in and have done over 200,000 since same diff

[rockcrawler31]

I agree about the speed you were doing having probably been low enough to be ok. If it was totally dry there may have been some galling on the gear faces as they heated up but i'm guessing that the residual film would have saved it for a while. When you pull it out have a look for any discolouring of the metal a la HAZ like you would find around a welded area of metal indicating that it has gotten hot enough to affect the temper of the metal. I'd be looking at the gear faces and bearings and any other area that is likely to see friction.

Otherwise just fill it up and monitor like others have said. No excuse not to come out to Watagans on friday champ

[Guy]

fix the studs, fill er up drive a bit and drop the oil, fill it again and keep an ear out for unusual noises.
At that distance and those speeds it is unlikley you have done any real damage.

[dogbreath_48]

Even if (and IMO that's a big if) damage has been done, it's unlikely the diff will fail in a catastrophic manor - if anything it'll just get noisy over time. I certainly don't think it's worth stripping it down for an inspection. As others have said just dump the oil after a few hundred k's. Make sure the drain plug has the magnet in it and that the magnet is still effective.

[bazzle]

5-10 kays there would be minimal damage especially at low speed

fix the studs wack in new oil, probabally drain the oil again after a few hundred kays incase theres some metal wear

x2 then listen for new noises :( hopefully non.

Bazzle

[shakes]

hey rob.
Its at high speed with no oil that the diff starts to heat up and can explode.

blew oil across the back of the car. Took two 1kg extinguishers and some blankets to stop it taking the rest of the car...






I agree with everyone else though. Drop the oil, replace after a couple of weeks, if there is metals filings replace again after another couple. and keep your eye out for a cheap centre to have on stand by.

[DUDELUX]

It should be alot better than the last rear centre you killed, it sounded like death when you drove up the road from my place.

[80's_delirious]

5-10 kays there would be minimal damage especially at low speed

fix the studs wack in new oil, probabally drain the oil again after a few hundred kays incase theres some metal wear

I would probably do the same.

x2

[80's_delirious]

Otherwise just fill it up and monitor like others have said. No excuse not to come out to Watagans on friday champ

hahaha!

x2 on this as well

[Elmo]

Cheers for all the input guys.

Have gotten it fixed or so it seems, mounted all back up and test drive seems good, no noises yet and seems fine... Time will tell if any heat affected damage rears its ugly head.

Used a Stud Eliminator kit from Locktup too, so in theory, the studs shouldn't pull out again either.

For those curious, Turns out it wasn't from impact at all, no contact with rock whatsoever. My springs wrapped themselves at a pretty severe angle and the pinion must have pointed to the sky pretty bad as after the two lower studs broke off, the studs from there on up actually held and pulled the mounting face on the diff out a good 1/4 inch. The reason we all thought the lower portion of the mounting surface had taken an impact and been bent IN was because that was the only part of the diff that was still in the stock position as the rest was pulled OUT.

Anyway, all good. A full day of metal manipulation and its back in stock shape. And a full day today of suspension fiddling and now have a hog wash mix'n'match combo set of leaf springs in and no more wrap.

Thanks again for all the input. Muchly appreciated.