24 replies to this topic

[me madjoe 90]

Why on earth should it be bad for the gearbox!?

As for a gear box to be lubricated effectivly it needs the oil level to onlycover one of the lower shafts or half way up the lower shaft as this lower shaft will pick up oil on its gears and then coat the other shafts gears efficiantly. This decreasis wear between the gears ect..... l

But with the mini gear box with it being the sump as well. The oil level is alot higher Any way wich is generaly bad for the gears as rather than them getting coated evenly they are submerged in oil and when rotating they throw the oil away from them rather like a propeller increasing wear as theres less oil between the meshing of the gears.

so i supose its just a gear box disign flaw. But there is method in my madness trust me

Actually most modern gears / gearboxes are nearly always fully submerged apart from final drive as this needs to be the quietest gear.

In a Mini gearbox they are constantly submerged in oil which means the lubrication is VERY VERY good. Instead of relying on the oil being thrown around it actually 'sucks' the oil into the gears meaning they are constantly lubricated.

My 998 did 1000 miles about a 1/4" below minimum and it caused no damage. It then ran for about 3000 miles and still counting at 1/4" above max with no problems. Though if you do overfill it it may lead to overpressurisation of the crankcase and cause the seaks to push out.

I would only use 20/50 oil, halfords stuff.


Does it smoke on throttle i.e down motorway, or does it smoke on overrun, when you are off the throttle and the engine is coming back down the revs?

Lee

Your therory is differnt to mine but think what you like i dont want to argue.

But i will say every one i know in the trade thats quite alot some who have been building gearboxes not just for minis but for new and old cars of many varitys will say what i say. And all manufacturer spesifications i have ever read and gone by have said to only ever fill there gear boxes no more than half full or there abouts.
Apart from some of the later Automatic Transmissions/semi auto as there a totaly differnt ball game and work on oil pressure and use torque convertors and sun planet and ring gears. with veriouse oil pressure contorlles clutches and brake bands.


And many apollogise to the O.P for having this long winded convo in there topic hope you manages to find why its burning oil.

Edited by me madjoe 90, 21 June 2010 - 12:28 AM.

[lawnmowercrap]

Why on earth should it be bad for the gearbox!?

As for a gear box to be lubricated effectivly it needs the oil level to onlycover one of the lower shafts or half way up the lower shaft as this lower shaft will pick up oil on its gears and then coat the other shafts gears efficiantly. This decreasis wear between the gears ect..... l

But with the mini gear box with it being the sump as well. The oil level is alot higher Any way wich is generaly bad for the gears as rather than them getting coated evenly they are submerged in oil and when rotating they throw the oil away from them rather like a propeller increasing wear as theres less oil between the meshing of the gears.

so i supose its just a gear box disign flaw. But there is method in my madness trust me

Actually most modern gears / gearboxes are nearly always fully submerged apart from final drive as this needs to be the quietest gear.

In a Mini gearbox they are constantly submerged in oil which means the lubrication is VERY VERY good. Instead of relying on the oil being thrown around it actually 'sucks' the oil into the gears meaning they are constantly lubricated.

My 998 did 1000 miles about a 1/4" below minimum and it caused no damage. It then ran for about 3000 miles and still counting at 1/4" above max with no problems. Though if you do overfill it it may lead to overpressurisation of the crankcase and cause the seaks to push out.

I would only use 20/50 oil, halfords stuff.


Does it smoke on throttle i.e down motorway, or does it smoke on overrun, when you are off the throttle and the engine is coming back down the revs?

Lee

Your therory is differnt to mine but think what you like i dont want to argue.

But i will say every one i know in the trade thats quite alot some who have been building gearboxes not just for minis but for new and old cars of many varitys will say what i say. And all manufacturer spesifications i have ever read and gone by have said to only ever fill there gear boxes no more than half full or there abouts.
Apart from some of the later Automatic Transmissions/semi auto as there a totaly differnt ball game and work on oil pressure and use torque convertors and sun planet and ring gears. with veriouse oil pressure contorlles clutches and brake bands.


And many apollogise to the O.P for having this long winded convo in there topic hope you manages to find why its burning oil.

Fortunately for me, Vauxhalls and Renaults are very prone to gearbox problems so I usually have to do a rebuild once every couple of weeks. Vauxhall are also very specific on how often the gearbox oil needs to be changed and the amount that is put in. Else to be honest I would possibly think what you do.
And sun and planet gears are also used in manual transmission in the diff, as they turn reciprocal motion into rotary motion.
Got a gearbox rebuild on an 09 plate Corsa VXR waiting for me when I get back off of holiday which i'm actually really looking forward to.

Edited by lawnmowercrap, 21 June 2010 - 09:00 AM.

[lawnmowercrap]

*double post*

Edited by lawnmowercrap, 21 June 2010 - 09:00 AM.

[cambiker71]

Why on earth should it be bad for the gearbox!?

As for a gear box to be lubricated effectivly it needs the oil level to onlycover one of the lower shafts or half way up the lower shaft as this lower shaft will pick up oil on its gears and then coat the other shafts gears efficiantly. This decreasis wear between the gears ect..... l

But with the mini gear box with it being the sump as well. The oil level is alot higher Any way wich is generaly bad for the gears as rather than them getting coated evenly they are submerged in oil and when rotating they throw the oil away from them rather like a propeller increasing wear as theres less oil between the meshing of the gears.

so i supose its just a gear box disign flaw. But there is method in my madness trust me

Utter rubbish, sorry but you really need to read the pink writing at the top before posting, anyway back on topic, the oil smoke sounds to me like a top end problem, did you have the head crack tested? Even a really small crack will do this, has it had any porting done, maybe it's broken through somewhere very slightly? Failing that it may well be a problem with the valve guides even if they are new. I'd have the head off and check it, but if it has a small crack or grind through in a port then it might be really hard to find visibly, you say it was ok with another head fitted? If so retry the other one and see what happens, hope some of this helps.

[stickycreambun]

I was going to say if you are stuck then although a bit of effort and cost swapping back to the other head would at least tell you if it was the head or rings, or something else. Good luck

[Cooperman]

Unless you have a central oil pick-up pipe, then you must run at over minimum. If you don't, good or bad for the geabox, you'll be buying new bearings if you corner at all hard due to oil surge leading to oil starvation.
On any long-distance rally Mini you need to slightly over-fill the sump, say 1/8" over max, to ensure that with the high oil consumption of, say, a 115 bhp engine, you don't run low on on long sections. The old 'Works' Minis were always slightly over-filled for this reason.
We are talking about 1/4" oil level difference between min and max, which equates to c.1 pint. That's hardly going to be the difference of the gearbox being 'swimming' in oil or just the lower positioned shafts covered, now is it. On any corner, the oil 'slops' one way and the other, exposing or swamping the gears, as does hard braking and acceleration.

[bmcecosse]

I agree! But I do think there is about 1/2" between Min and Max. I certainly noticed surge even when running a bit over Max, until I fitted centre pick-up pipe. And the slightest bit of surge with no oil pressure soon wrecks the bearing shells.
As for the 'low oil is better for gears' - dear oh dear......... or as we say up here - Aye Right!

[me madjoe 90]

Oh well think what you lot wish but....... i dident necereseraly mean ever single gear box but most are never filled full for a reason and i was just pointing out mini gearboxes seam to be an exception.

Also lawnmowercrap i know how a diff works and no need to get all arsey about it. obviously you think your gods gift so carry on. Do it the way you do it

But im not wrong it makes sence.


I Know that its bad to under fill a engine with oil, and i was just pointing out that its bad to over fill a gear box, since a minis shares the same oil i think its a good idea but has its set backs and would say id fill it between mini and max lake any other enigne, but i would never over fill a seperate gear box due to the facts i mentioned earlyer.


Oh and hears a site that agrees and shows points on why its bad for gearboxes to be over filled like what i mentioned. http://www.bobistheo...;Number=1563253

Edited by me madjoe 90, 21 June 2010 - 06:07 PM.

[valve bounce]

ive got a central oil pickup, also the oil pressure is around 50psi when warm so thats all ok. but im really stumped the other day i did an oil change and i tipped the full 5liters in as you do but this didnt even reach the min mark on the dip stick (about 5mm or so short). now i might be wrong but i thought it should be alot further up. now i was wondering if i havent got the dipstick hammer in far enought therfore when im filling it up to max its actually alot fuller than it should be.

thank everyone this is helpfull

[the.stroker]

Topic closed , if any individual would like it re-opened and are prepared to have a sensible debate without the use of personal insults feel free to PM me