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gearbox oil - bob
what is the general opinion on the frequency of manual gearbox oil changes on a modern car?
Re: gearbox oil - honest john
I say change it once, early in the car's life (after the first year) to get rid of any bits of swarf thrown off during the bedding in process. Otherwise those little bits of metal get ground down into tiny filings which eventually find their way into the bearings. Comments on this are welcomed, though.

Re: gearbox oil - Michael
i haven't changed the gearbox oil on any car since the early 80's. The last one was my Triumph Dolomite and I guess that was a last ditch effort to try and make it better (the gearbox was not strong enough for the 1850 engine. I seem to remember it being designed for the herald).
Since then, I have had 6 new cars, each accumulating 100k miles and never changed the gearbox oil but never had any problems either. Not saying the oil should not be changed, just that I haven't nor have I had any problems.
It's one of those conundrums, change oil and do not get problems = oil change essential. don't change oil and do get problems = oil change essential but also, don't change oil and don't get problems = oil change unnecessary. Difficult to prove, but, given that changing the oil does no harm, maybe it's better safe than sorry.
Re: gearbox oil - andy sampson
Just loking at this one myself and cant decide if to change or not, Haynes manual says to change every 4 years, Volvo says it should never need changing (Volvo 480 Turbo 1991)??????????

What to do?????
Re: gearbox oil - Ben Chapman
Change it. Even if there were no stray bits of metal left in the box after manufacture, the gears will naturally wear, leaving bits of metal to ruin your gearbox. Gearbox oil may not be contaminated by a combustion process like an engine, but wear will take place. You change an oil filter on an engine becasue it becomes full of undesirable material. However, people just leave crap floating aorund in their gearboxes. I think its best to use a magnetic sump plug to try and keep this stuff away form my bearings.
Changing to fully synthetic oil, like Mobil 1 75W-90 gear oil will also improve the gearchange if a mineral base oil has been used at the factory. It is not true that a mineral base oil will not degrade after 100k of use.

Re: gearbox oil - Mark
Must say its worth doing, had a 94 Astra 1.7d and out of curiosity I changed the gearbox oil at 70k. The cover whcih comes off to allow you to drain the oil (no plug) had a baked tar like resin on it (inside) and the oil seemed very thin. Whilst cleaning up the insides of casings several hard lumps of gunk were found and when I looked in the bottom of the oil pan some small shards of different metals were visible.

The fully synth oil that replaced what came out cost about £17 and the cover gasket was about £2.50. All told took about 1.5 hours which included the time taken to polish up the inside of the casing cover.

as ever

Re: gearbox oil - Michael
how often do you think it should be changed, Ben?
My schedule for transmission oils. - David Woollard
I change the transmission oil about every three years on our own cars, two yearly on the Land Rovers.

I advise customers to keep to a similar schedule but respect their wishes if they disagree.

Gear oil (or engine oil if that is the correct fill) is so cheap and a sensible labour charge should be no more than 30 mins, so why not do it for peace of mind?

Re: My schedule for transmission oils. - Michael Thomas
I had the gearbox oil changed in mine at 24K, it cost £25 and it was just as a preventative measure as it was an auto box. Haven't changed it since, maybe will at 72K. The garage I took it to thought it's a good thing to do but purely based on preventive maintenance than anything else.
Re: gearbox oil - Ash Phillips
I had an Alfasud Sprint in the 80s and it had the typical rubbery box, which was actually very quick and slick apart from the poor gate (whatever gear you were in the lever seemed to lean back to the middle neutral position). After about 70k it went all awkward to engage and started slipping out of 2nd when giving it some. There was no set change interval (I think), but the word from a man in the know (60s Alfa rally champion, so he says) was "they all do that..." change gearbox oil with standard oil, run for 1k then change again. It worked like a charm. The gearbox was perfect, right up until the car finally dissolved at 110k.

I think I know how oil works, but have never been able to see how it could make such a difference. But what a difference!
Re: gearbox oil - Keith Bassett
"I think I know how oil works, but have never been able to see how it could make such a difference. But what a difference!"

My thoughts exactly after a recent experience. I acquired a Citroen AX (1997) for my daughter to practice in while learning to drive. Gearchange was appalling, particularly into first & reverse. Difficult to tell whether it was fully engaged and often had to let clutch up very gently and listen for a crunch. Frequently needed extreme force to get it into these gears. Took car to a Citroen dealer who thought worn bushes in the linkage would be the cause. On collection, they said bushes were not worn but they had greased the linkage and everything was O.K. Needless to say the fault was just as bad as before. Car was very unpleasant to drive and totally unsuitable for a learner driver or any driver come to that.

Before taking it to another Citroen dealer, I thought I would change the gear oil with no expectation that it would make any difference. Officially, the gear oil lasts for the life of the car. I used the 'official' oil (Total BV Improved) and it completely cured the problem. No gear selection problems at all in 2 months and my daughter has no problems with the gearchange. After fearing that expensive work would be necessary, I was delighted to cure the problem for 6 quid. The car has done 34000 miles (bought new originally by my son).

How can the old oil have had such a devastating effect ?

Keith Bassett
Re: gearbox oil - Vin
The following comes from memory from an article on oil in a bike magazine years ago.

Basically, a gearbox is the most destructive place oil can be. Oil is crushed between gear cogs and the strands that make up the oil (and which give it the lovely lubricant properties we all love) are physically cut. The end result (long term) is oil that has no power to lubricate. At this point, crashing the cogs together - which is what you do each gear change - is going on with little or no lubrication and hence is difficult. Even moving the gear lever through the gate becomes difficult.

Now that car servicing is based solely upon fleet requirements, the long term nature of this problem is swept under the carpet by saying "no need for a change". Fine for the 60K miles of the average fleet car, but problematic if you like cars to last a while longer.

If your car has shared engine and gearbox oil, all the more reason for regular engine oil changes, by the way, as engine oil definitely isn't made to last in a gearbox.
Re: gearbox oil - Mark
True enough especially for unit construction m/c engines where the same oil that lubes the cam and pistons also lubes the gearbox.

Within a short space of time all sort of nasties can be floating in the oil with damage to one or the other.

From what I have seen the cams usually go first due to clogged oilways in the head.

Sensible unit contruction motorcyclists usually change oil every 2/3k.

Different story for those with pre-unit jobs such as earlier BSAs etc, you have the luxury of being able to put the correct oil in the correct part of the engine/gearbox and if you are flush change it to match the SAE to the seasons. Much longer life excepting crap design of most british stuff and assuming it does not leak out as fast as you put in it.

Most cars are pre-unit in as much as they have seperate gearbox/engines each using own oil and not sharing it.

Plenty of room however for adding thick grease, bananas, sawdust however to a failing pre-unit gearbox if one is so inclined.

as ever

Re: gearbox oil - Michael
useful info, Vin. Do motorbike gears crash together each gear change? The gears in the car boxes I have rebuilt are permanently engaged (except the reverse gear idler.
Re: gearbox oil - Vin

B*ggered if i know - as I said, it's from memory from an old article - but whatever moves when you change gear doesn't do it lubriciously once the oil has broken down.

Incidentally, why are cars just waking up to sequential gearchanges, i.e. lever back to go up a gear, forwards to go down, when bikes have had it since the 1930's?

Re: gearbox oil - Mark (Brazil)
> it lubriciously once the oil has broken down.

I'm prepared to be impressed as soon as 1) I'm convinced that's a real word and 2) I can work out how to pronounce it.
Re: gearbox oil - Vin

Good enough, Mark (Brazil)? Lucky, really, as I did make it up.

Re: gearbox oil - Mark (Brazil)
I'll bide my time and drop it in on another conversation and see how I get on.
Re: gearbox oil - Vin
Erm, watch out for definition 3 on the above link(!)


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