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i can appreciate what you're saying, and no, i wouldnt expect heat to do much to ATF apart from burn itQuote:
Originally Posted by Blknight.aus
what im looking at is ATF's ability to handle metal on metal stress, automatics have little metal on metal stress, only in the bearings, but in the gearsets of a manual gearbox lugging a couple of tonnes of 4x4? i doubt thats the kinda of stresses the industrial chemists were look at when they formulate ATF's
you heard of planetary gears......?
those little gears which act on them big ones.......im sure theyve got a fair bit of pressure on them.......
and its metal to metal......you will find these in a diff as well......
a diff runs thick gear oil.......
the automatic transmission runs these gears as well......
along with clutches and friction plates.......and all the other methods for destroying oil......
including lots of heat.......and they are designed to run auto oil.........
it is a gear oil.......just a bit thinner.......
there are different types and grades of all oils......
auto oil is just a different grade of gear oil.......
there are better auto oils today than when these gearboxes were designed.......
so maybe running a better quality oil will last longer........
maybe they did get it wrong from the start and should have had gear oil them from the factory........
the only way to know is either by trial and error......or by destructive testing.......
personally.......i would prefer a light gear oil to replace the transmission fluid.......
you can get thinner gear oils today which werent available when those boxes were made.....
must be the closest thing to auto oil........
there are even boxes that ran on engine oil out there......
work that one out........
best thing to do with anything that requires oil or grease.......is to regularly change it.......
so that it has fresh oil or grease all the time.....
it needs to be replaced before it breaks down and loses its lubricating qualities......
this is more important than which oil is used........methinks......
(more later..... ok so it was the next day)
ok so Defenderzook covered most of the points I was going to make but missed one.
where your ATF type oils do not cut the mustard is situations where you have large gaps to deal with IE diffs, the backlash spacing in the pinion/crownwheel teeth is enough to let the ATF get squeezed out so you wouldnt use it there.
In a manual gearbox thats in good nick ATF is the way to go the tooth to tooth contact (especially in helical cut gears) is such that there isnt enough room for the ATF to escape especially as they are generally submerged at the point of contact. That begins to change as the gearbox wears out as ATF doesnt have as much "cushioning" effect as thicker oils its less able to deal with the additional movement and spaces of a worn box.
Dont mark that as something against ATF fluids by the time your box is worn out enough to make ATF substantially less effective as the primary oil its time to rebuild it back to specs. Yes a gearbox will hang on long beyond this time but your gambling with a few factors including the potential to damage the casing in a manner which renderes it unable to be reused so instead of a rebuild you have the cost of a replacement.
d'oh, forgot about the planetaries, i still reckon thered be more shear/shock load in a manual box though
*meh* still think its a bad idea running ATF in a manual
While the autos still have a gear system, there are 3 planetary gears to share the load. The pressure on the mating surface of each gear is lower so there is no need for a heavy oil in an auto. With a manual, all the load is applied to the gears that are engaged so a thicker oil is required due to the higher pressure at the mating surfaces.
I think that the helical cut on the gears in an auto box is at less of an angle too. If so, this increases the size of the mating surface and also results in less pressure.
The clutches and friction plates are again a large area, so a thick oil isn't required.
Still not sure why LR reccomend ATF in a manual box though :huh:
because when the oil was specified the only thing available with the required viscosity was ATF or engine oil. There weren't any low vis manual trans fluids.Quote:
Originally Posted by awabbit6
Regarding Lubrizol, they are one of the biggest additive companies in the world. ie, they are the ones that develop the additive package to meet whatever API or ASEA specs the oil blender wants to meet, then the blender blends those adds into their base oils.Quote:
Lurizol
If Ford specced a Lubrizol additive it could be one of hundreds they produce. In other words, Lubrizol is a company, not an additive.
it's coincidence, not cause. You've had a component failure that would have occurred regardless of the lubricant used.Quote:
Originally Posted by joel_nicholson
im not 100% convinced the lubricant is without blameQuote:
Originally Posted by rick130
*meh* still think its a bad idea running ATF in a manual...
V8 touring car gearboxes work pretty well with ATF
V8 touring car gearboxes probably get rebuilt/serviced a bit more frequently than your average gearbox.
ATF?? Never had gears chewed until it happened in the R380 running ATF. While I was at the gearbox reconditioners the proprietor showed me another R380 which had chewed the gears like in my box. Input gear on first of the gears on the laygear just chewed each other up. During the time I have had the vehicle I have never towed in 5th and when the failure got to the stage I could hear it and feel/smell the heat coming from the box I was not towing either.
I was under the impression that LR no longer recommend ATF for the R380 and that is why the MTF94 was produced by Caltex/Texaco. I would say that this must say a lot for the ATF argument.
I took the following snippet from the difflock forum
http://http://forum.difflock.com/viewtopic.php't=17098&highlight=mtf94
"ATF was originally specified for the LT77 5-speed gearbox and, theoretically, could be used in the later R380 box. Type DIII is the best grade currently available. ATF was originally specified because of the weak synchromesh in the LT77 and R380 boxes (especially second gear).
ATF has a very low viscosity (rated as 5W20 since it falls below normal gear oil viscosity grades) and so it has minimal drag on the gears, enabling the weak synchromesh to do the best of a bad job.
BUT ATF has several drawbacks which is why it is NO LONGER recommended for use in such boxes. These are:
It is generally a plain mineral base stock formulation (even DIII) and this, coupled to its very low viscosity, means that it is poor at preventing metal to metal wear in manual transmissions.
This is compounded by the fact that the viscosity improvers within (thickeners) are more rapidly sheared down in manual transmissions. Again, this reduces the protective film strength of the ATF in those areas of high pressure contact and also increases transmission noise. "
Joel,
Stick with the synthetic, your gearbox has failed and like someone else said it is a coincidence that it failed at a time when you changed gear oil type.