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i have a astra 1.6 16v 2000 model at present on 61.000mls i have never dropped the gear oil , how often should it be changed, when the clutch needs replacing? or every 3 years? im interested to know it looks simple enough there's a plate under the box with 6-8 bolts in do you drop it here? please any advice welcome thanks tony.
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I wouldn't bother unless the gearchange is getting notchy or the clutch needs replacing. There's usually a plug at the bottom of the gearbox for draining the oil, and another halfway up for filling - this also acts as a "maximum" mark, because any excess oil just comes straight back out.
I wouldn't bother with changing the oil, maybe check the level if you're worried about it. If you do decide to go ahead, make sure the filling plug unscrews easily first, otherwise you might find yourself with an empty gearbox and no way to fill it. The oil you use is much thicker than engine oil too, usually 75w85 or similar.
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thanks for the replies it looks like a pain in the bum to change it so i'll leave it till its time for a clutch.
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I think that the gearbox oil is a bit difficult to change on these, because there are two reserviors, one for the gearset, and one for the final drive. The oil you pour oil into fills the gearset reservoir - the overflow from here fills the final drive, which is where the level plug is. The plate you refer to drains just the final drive. It isn't simple to drain the oil in the gearset - if you need to do this, you need to partially dismantle the gearbox, by sliding the gearset out of the end of the gearbox.
To avoid having to strip the gearbox to change the oil, I would drain the final drive, and refil the gearbox - drive around for a bit, and drain the final drive, and fill the gearbox again. I would do this a few times, and then renew the final drive sump gasket and top up the gearbox.
I think the oil is ATF Dexron, but check this before buying any (yes, I know it's a manual, but I **think** ATF is the right spec.)
Number_Cruncher
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what a kerfaffle NC think i would suffer the consequences if this is the case
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oddly enough oldman, I can count on the fingers of one thumb the times I've done this for a customer!
Usually, the worst that happens to these gearboxes is that the bearings fail. If you change them quickly enough, the gearsets don't suffer too much, and the bearings aren't too difficult to do.
Number_Cruncher
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ATF in a manual box!! Has the world gone mad?!
I just assumed most standard 5-speed gearboxes were as simple as the one on my car - obviously not! If Number_Cruncher's right, I'd leave the box alone - it'll be fine for the life of the clutch!
The idea of removing a plate to drain the gear oil doesn't appeal - is there a gasket between the plate and the box? If so, and it gets dirty during your oil-change, you could end up causing a leak - would be best left alone IMO!
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If its the same as the Vectra the oil is a bright red colour. Is this ATF?. It was also the same in a Nova we once had.
Once again referring to the Vectra there is a level plug on the gearbox but according to the Haynes book it warns that it must NOT be filled through this, but instead through a plug on what I can only describe as a box where the gear lever selector enters inside the engine compartment.
I assume the reason for this is what NC is describing.
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A lot of people use Dexron II or III in these manual transmissions, but strickly speaking you should only use GM oil 1940764 (90540998) - this is a less friction modified ATF. I think it is only made by Motul and only available though the dealer. You'll need about 2 litres. Using Dex III gives a less quick synchro action.
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i think this actually depends on which gearbox is fitted?
And dexron by the way is a gm only term for a type of oil. just thought you might like to know that bit !
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i think this actually depends on which gearbox is fitted?
I was quoting for a 2000MY Astra 1.6 - the car in question.
And dexron by the way is a gm only term for a type of oil. just thought you might like to know that bit !
'Dexron' is a GM trademark for a type of automatic transmission fluid. GM publish the specifications for each variant of Dexron and many lubricant suppliers then manufacture oil to the relevant GM Dexron specification.
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Ok, but it just shows how difficult this gets because this car can be fitted with different gearboxes?
My info gives me 2 types of fluid depending on which box is fitted. But have been to dealers before about subjects like this and nearly always get told, we only use this 1 fluid!
I have Opel numbers, 1940764 and 1940768 depending on gearbox type fitted.
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In the USA, where the majority of cars have auto transmissions, I believe the major manufacturers like GM have used ATF for both auto and manual boxes to simplify the lubricant supply and fill process as both types go down the same line ( maybe save a few cents per unit too).
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In the USA, where the majority of cars have auto transmissions, I believe the major manufacturers like GM have used ATF for both auto and manual boxes to simplify the lubricant supply and fill process as both types go down the same line ( maybe save a few cents per unit too).
The characteristics of ATF and a typical modern manual transmission lubricant (e.g. Castrol SMS-X) are actually radically different. ATF is much thinner (by about 30% at 100deg) and typically has a GL rating of 1-2 versus the 4-5 of an MTL. Therefore a transmission has to be designed with a particular lubricant in mind. Putting ATF in a 'box that should take an MTL can result in serious wear and poor gearshift quality.
Quite a few manual boxes were designed to run an ATF to give better cold weather shift feel (better synchro action) and also better fuel economy.
These days a lot of manufacturers are moving to very thin synthetic 'proprietory' MTL's - these are nearly as thin as an ATF but have different friction modifiers to improve synchro 'bite' and anti-wear and EP additives to give a GL-4 or GL-5 rating to improve durability of the transmission. USA GM cars with manual transmission now run with their special 'Synchromesh' manual transmission fluid.
Modern manual gearboxes are very complex and MUST use the factory specified oil - only change to a different oil if you know what you're doing.
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