This can't be right - can it?

JohnD · Post by **JohnD** » 05 Dec 2005, 18:20

I came across this topic on one of my other forums. Can't say I would like to go along with his advice, other than the first sentence. What do you think?

Choose a good brand named oil (Fully synthetic 5/40). Once you have changed your oil and filter start the engine and then just listen to the tone of the engine. and to go one better refill your manual gearbox with it and then no more stiff 2nd gear.
oh and by the way the oil aready in your g/box is most likely to be an SAE30 type oil = 15/40
I have tested this oil in my own diesels for many years now and in the last three
motors i have put it in the axles as well.

AndersDK · Post by **AndersDK** » 05 Dec 2005, 18:37

At least the g/b is still lubricated

Post by **Peter.N.** » 05 Dec 2005, 19:04

Sharp intake of breath! While some gearbox's use engine oil I have never known I rear axle that used it, I would have thought that the pressure would have broken the film down.

bxbodger · Post by **bxbodger** » 05 Dec 2005, 21:13

BL gear-in sump diffs were o.k. on multigrade as were the back sloping PSA 1400 engines, but then they were designed for it in the first place- I certainly won't be putting multigrade in the back axle of my Triumph, however!!!!!

citronut · Post by **citronut** » 05 Dec 2005, 21:28

yes but the cars with gear box in the sump,the gears dont rely on being splashed with oil they are mostly submersed in oil,normal gear oil is stickyer than engine oil
regards malcolm

London luke · Post by **London luke** » 05 Dec 2005, 22:24

I am using Halfords 10/40 semi synthetic. Is this a problem ? The car is a 1.9Td Xantia 1998.

Going to change it next week and do a Forte oil flush.

AndersDK · Post by **AndersDK** » 06 Dec 2005, 06:23

London luke wrote:I am using Halfords 10/40 semi synthetic. Is this a problem ? The car is a 1.9Td Xantia 1998.

Going to change it next week and do a Forte oil flush.

We are talking gearbox oil - not engine oil. A suitable gearbox oil would be any non-sulphur additive 70W/80W specified to GL-4. All this translates to a good "old fashion hypoid gearoil". You should never replace this oil during lifetime of the gearbox. Only if the LHS driveshaft is removed and the oil then have to be drained.

The mentioned oil is perfect for your engine. BTW : why do a Forte oil flush in the engine ? Its a money & time waster with the oil quality you get these days. The important thing is to obey the oil change intervals.

wilkobob · Post by **wilkobob** » 06 Dec 2005, 14:25

Slightly off topic but... I now drive a ford mondeo (I know, slate it if you must) but the gearbox on that was awful in mornings (very stiff). I asked about for advice and was told it would be a good idea to change the gearbox oil. Having done this, the gearbox is much smoother. I have also had similar problems on my old ZX estate diesel, where changing the gearbox oil solved all problems of notchy 3rd gear and stiff changes. The oil used was always gear oil, cant remember the type though.

Homer · Post by **Homer** » 06 Dec 2005, 17:58

wilkobob wrote:Slightly off topic but... I now drive a ford mondeo (I know, slate it if you must) but the gearbox on that was awful in mornings (very stiff). I asked about for advice and was told it would be a good idea to change the gearbox oil. Having done this, the gearbox is much smoother. I have also had similar problems on my old ZX estate diesel, where changing the gearbox oil solved all problems of notchy 3rd gear and stiff changes. The oil used was always gear oil, cant remember the type though.

Either it had the wrong oil or not enough of it before the oil change.

BX's can be bad for 2nd gear balking if they don't have just the right ammount of oil.

madmanbob · Post by **madmanbob** » 08 Dec 2005, 06:05

JohnD, This must be a joke! I like the statement "SAE30 type oil = 15/40 ", since when did 30 equal either 15 or 40? Your 30 is a straight oil that will be a viscocity of a 30 grade all at all temperatures, wheras the multigrade will be the viscocity of a 15 when cold and a 40 when hot.
Engine oil is designed to lubricate in hot environments (the engine) whilst coping with the by products of combustion. Axles and gearboxes (apart from minis) have no combustion by products, no extremes of temperature but require an oil that withstands high pressures with a good shear strength, in otherwords a completely different oil.
Perhaps one ought to fill our cars up with a 50/50 mixture of diesel/petrol, after all it is all fuel.
The worry is that someone here might take some notice of this joke and try putting engine oil into the gearbox and axles of cars. They will have an expensive failure eventually.

madmanbob · Post by **madmanbob** » 08 Dec 2005, 06:08

Think I'll buy an old mini, no axles and no seperate gearbox, think of the money I could save on oil! but there again, I never had a mini that had the economy or performance of a Xantia HDI.

jeremy · Post by **jeremy** » 08 Dec 2005, 06:48

And remember the other advantage of the Mini setup - when the gearbox breaks up the bits get into the engine bearings as well as I found to my horror - and oil pumps are only moderately efficient as filters.

Incidentally didn't the Peugeot 'Suitcase' engine use this arrangement as well (as fitted to the first BX 14's?)

NiSk · Post by **NiSk** » 08 Dec 2005, 16:49

Ah - but the Mini had a separate diff/final drive housing that was completely separated from the gearbox/engine sump construction.

Many front engine-rear drive cars use engine oil in the gearbox (BMW, Mercedes, Volvo, ford Scorpio's etc etc.) But they have back axle/diff that'd filled with hypoid oil. If you put ordinary engine oil in a final drive/differential using a crown wheel and pinion drive (i.e. most cars) then it won't last very long! As maddy said, hypoid gear oil has very high shear strength, and it needs it!

//NiSk

jeremy · Post by **jeremy** » 08 Dec 2005, 17:16

No separate lubrication for final drive on a Mini - and the same gearbox bearings that collapsed from 1958 to the present day - such is progress!

Early axle oils were 'EP - extreme pressure' which were OK for spiral bevel crown wheel/pinion setups (drive goes in at axle level). Late 40's saw the introduction of the 'Hypoid' drive (drive goes in below the axle level) which needed special oils to cope with the sliding friction.