Manual Transaxle: OVERFILL for lower temperature & longer life?

[Wildthings]

What I have done on several (non VW) gear boxes, automotive and industrial, over the years is go to a thinner oil (like a 10w30, 5w50, or ATF) and raise the level significantly. The gear boxes I did this to had various problems to start with:

-so little oil capacity where even a minor leak would quickly become fatal.
-a box with a foaming problem
-a box that had a history of running hot
-a box that isn't lubricating one of the upper bearings well
-poor synchronizer function
-a box running at extreme angles

An easy way to get extra oil into an otherwise stock Vanagon box is to just run the tires on the side of the fill plug up on a curb so the box sits at an angle.

[metropoj]

interesting ponderings.

So, I thought I read somewhere that VW dropped the oil fill level to also make it easier to shift ?

So, in theory, wouldn't making the oil level higher make it more difficult to shift ?
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John.
86 TiiCo powered Westy.

[Wildthings]

[Spezialist]

The detergents in transmission oil, have two purposes to clean and reduce foaming. Need some handcleaner on the road? Fresh trans oil will clean it, then rinse with plain water.
Adding too much oil will result in seeping and probably less cooling since throwing gears will be in cavitation.
Keeping the gearbox clean and working the vehicle within specs is your best bet.
Example, don’t carry canned food or too much water on long trips. Towing? Better hit a scale.
Learning the limits of the vehicle “it’s duty cycle” will give you longevity with reliability and durability over trying to outthink engineers with billions of miles of experience in their education.
Just my opinion
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[Sodo]

[Waldi]

[zuhandenheit]

[Sodo]

[Waldi]

Sodo stop to quote things from me that i ve never sayed.

I dont care what you or others do.
Dont sound like like a "Specialist"
You are not.

[Sodo]

[Waldi]

Whats hard to understand if i say, if you want to be sure not to get broke on the street its better to check the box every 100k km than to change, cool, filter the oil, and drive it untill something breaks. Especialy with stronger engines driving without feeling.
Cheking the magnet helps here a bit, but not at all.
No need to change the oil if you use a good one. Leave it over night, fill it in again without the dirt (if there is any) on the button.

VW reduced the oil on gazer engines and on SA gearboxes with oil plates to avoid foam on high revs and for easier shifting.
Easier shifting means less wear, so less contermination.

What Specialist has sayed about cleaning with oit, counts to the new synthetic oils but not for the old or cheap oils.
Thats why you should not fill synthetik oil into a old gearbox.

[Waldi]

Lucky i am disensambling 3 boxes today. You get fresh on topic pics
Thats the 3rd one. A 16 Syncro box. Was never open but somebody changed the old oil for synthetic one. Would not surpirce me if i find something inside that they tryed to repair with oil

[Sodo]

[Sodo]

But the subject of the thread is "Manual Transaxle: OVERFILL for lower temperature & longer life?"

The subject of contamination is off-topic. There is no point in exploring methods to prolong transaxle life if you are not doing the most obvious FIRST step, which is minimize/remove abrasives in your lubricant.
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'90 Westy EJ25, 2Peloquins, 3knobs, pressure-oiled GT mainshaft, filtered, cooled gearbox
'87 Tintop w 47k 53k, '12 SmallCar EJ25, cooled filtered gearbox
....KTMs, GasGas, SPOT mtb

[Waldi]

Sodo i think not to awnser to you anymore, cause its wasted time for me.
I leave you alone with your fantasies and change to the "failures and solution" thread.

[Sodo]

[Waldi]

No we dont agree, as you mix what i say with your believings.
This is like mixing french foot with american foot saying it is better.

[Zeitgeist 13]

Cajun foot ftw!
_________________
Casey--

'89 Bluestar ALH w/12mm Waldo pump, PP764 and GT2052
'01 Weekender --> full camper
y u rune klassik?

[Sodo]

Waldi I think it’s even more clear the problem is a german/English communication error. Even though your English is good.

But I just had a sudden craving for Jambalaya....
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'90 Westy EJ25, 2Peloquins, 3knobs, pressure-oiled GT mainshaft, filtered, cooled gearbox
'87 Tintop w 47k 53k, '12 SmallCar EJ25, cooled filtered gearbox
....KTMs, GasGas, SPOT mtb

[IdahoDoug]

On the subject of overfilling, I am curious why people think it leads to foaming? I'm just trying to get some brainpower on it so I'll just give a "stream of consciousness" here as if we were sitting around a campfire.

Foaming happens when an object (a gear tooth) enters oil from air at a high enough speed it creates an "air hole" in the oil behind it that cannot collapse fast enough to avoid being drawn into the oil. Obviously, many teeth, many holes and a continuous process of creating foam.

In the Vanagon gearbox, the lowest gears would presumably be unable to create foam because they are fully immersed and their teeth don't swing up into free air. So, what if we filled it up high enough ALL gears were immersed? Theoretically, as long as there is enough air space to allow for heat expansion, seal pressure would only increase whatever the psi increase is for another - what? - 2 inches of oil? (BTW - simply put a short hose and common cheap fuel filter on the vent tip to prevent contamination. Water wading? Make it a few feet long and terminate it up by the taillights as high as you want. Common LandCruiser trick. Mine are all elevated about 4 feet high.)

Gear shifting issues would be the reason VW lowered the oil by 15mm or whatever, btw. The cold shifting issue is likely the worst of it, and its caused by the gears being spun by rotating oil and gear teeth not mating, leading to either grinding or what a consumer calls "stiff" shifting when the teeth don't line up like the synchro intends. So they must have determined lowering the oil lowered the sympathetic spinning by oil of the undriven gear you're trying to engage. It would therefore be reasonable to assume that overfilling would cause this issue, but a patient and caring driver/owner/tech savvy type could easily adapt to it.

A comment on gears. In this trans, the lower gears on the pinion shaft stay at ground speed and are always slower than the upper shaft gears. The upper mainshaft gears are engine-RPM. So worst case for the trans in causing foaming or cavitation is high-RPM hill climbing with heavy gear tooth pressure. Best case is cruising along in top gear.

A comment on gear lube. Generally in a gear case, the oil "climbs" up the partly immersed upper gears as a layer of oil you can see, most is flung off at higher RPMs and the gears are wetted all the way around. But the contact points (our main shaft to pinion shaft gears) are generally immersed and transfering heat away through the oil. With foaming, that critical heat transfer is reduced.

I like the linked article on gearcase lubrication. Switching topics slightly, I think it's wise to know that when people recommend things on other threads like putting diesel fuel, trans oil, kerosene into engines to clean sludge and the like that tiny leftovers of the wrong fluid can affect things dramatically. Such as the article's example of a company having foaming problems tracing it to a tiny residue of a cleaning solution. So be wise and cautious when trying to outsmart the engineers on fluids.
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1987 2WD Wolfsburg Vanagon Weekender "Mango", two fully locked 80 Series LandCruisers. 2017 Subaru Outback boxer. 1990 Audi 90 Quattro 20V with rear locking differential, 1990 burgundy parts Vanagon. 1984 Porsche 944, 1988 Toyota Supra 5 speed targa, 2002 BMW 325iX, 1982 Toyota Sunrader