930 transaxle puking fluid?

Alex

Active Member
#1
I have a non-inverted 930. At the top towards the front of the unit there is a swivel fitting that vents fluid. The fititng does not connect to anything, it just sits exposed there pointed rearwards. Any time it's really hot outside, driven hard or on the dyno the vent fitting pukes fluid out.

Instead of just having a fitting that vents into the air (and thus all over everything :/ ), should I be routing a hose to a catch can?

If so, what size line should i be using between transaxle vent and catch can(e.g., -8?) and what is the threat pitch and type of the fitting on the top of the 930 (again, non-inverted)?

Also, should the catch can be a sealed unit or vented to atmosphere (i.e., open with a filter)?
 

Randy V

Administrator
#2
I think you answered your own question.
I would say that a -6 should be sufficient, -8 would be overkill.
Knowing you, there will be a -10 installed.... :D
 
#3
I didn't want to add yet another catch can to the rear of my car, so I instead inserted a 1/2" fine-thread stud into the 1/2" hose attached to the vent tube (close to that tube), which is attached to a filter-breather mounted higher than the vent. This allowed the air to expand out when the case gets warm, but has kept the case clean of oil as compared to it doing the exact same thing you've noted. I'm thinking if you use a can, it should be vented, otherwise, you've negated the purpose of the vent (at which point, you might as well seal off the vent).
 

Alex

Active Member
#4
I didn't want to add yet another catch can to the rear of my car, so I instead inserted a 1/2" fine-thread stud into the 1/2" hose attached to the vent tube (close to that tube), which is attached to a filter-breather mounted higher than the vent. This allowed the air to expand out when the case gets warm, but has kept the case clean of oil as compared to it doing the exact same thing you've noted. I'm thinking if you use a can, it should be vented, otherwise, you've negated the purpose of the vent (at which point, you might as well seal off the vent).
but by having it vented arn't you exposing the fluid to air (moisture) and thus reducing its life?

If you just sealed it off then the fluid would have nowhere to go and start pushing out seals and stuff .... a non-vented catch can the fluid would push out of the transaxle and into the can. But then on the other hand as heat causes air to expand I think it needs a vent to vent to atmosphere to release pressure?

I can see arguments for both a vented and non-vented solution. I think the vented solution would be ideal, but not certain because of effects of exposing gear oil to air


I think you answered your own question.
I would say that a -6 should be sufficient, -8 would be overkill.
Knowing you, there will be a -10 installed.... :D
I'm scared of using too small and accidentally causing a restriction that causes seals or whatever to blow out :O
 
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Randy V

Administrator
#5
I have not heard of any hygroscopic gear oils. Filtering the vent would be a good idea. Sealing the gearbox up is just begging for a blown seal...
 

Alex

Active Member
#6
I have not heard of any hygroscopic gear oils. Filtering the vent would be a good idea. Sealing the gearbox up is just begging for a blown seal...
that's what i was thinking, but in Alex's wonderful world of engineering everything is a potential hygroscopic/abrasion/ fire risk ;)

now i just need to figure out what the thread type/pitch/etc.. is of that fitting and i'll be in business.
 
#7
but by having it vented arn't you exposing the fluid to air (moisture) and thus reducing its life?

If you just sealed it off then the fluid would have nowhere to go and start pushing out seals and stuff .... a non-vented catch can the fluid would push out of the transaxle and into the can. But then on the other hand as heat causes air to expand I think it needs a vent to vent to atmosphere to release pressure?

I can see arguments for both a vented and non-vented solution. I think the vented solution would be ideal, but not certain because of effects of exposing gear oil to air

I'm scared of using too small and accidentally causing a restriction that causes seals or whatever to blow out :O
If the entire system is truly sealed (by having a non-vented catch can securely hosed to the transaxle without leaks), then there would be no pressure differential between the case and the can, to push fluid all the way to the catch can (even for the unlikely event that the tube is completely filled with fluid, and not a combination of fluid and air). Every transmission/transaxle/engine has a vent, so I'm guessing that the limited exposure to air (moisture) is not a concern in the manufacturer's design.

My box is inverted, and mine pushes oil out because oil is constantly being slung by the ring gear straight at the vent tube. Adding a pressure differential due to transaxle heating, the fluid is pushed on up the vent tube and to the filter. The tiny restriction in the tube allows the slow release of that pressure, and keep oil from being thrown out after the temperature peaks, and allows any oil that has passed, to drain back into the case after temperatures have stabilized.

I believe a proper fix for me is to relocate the vent tube to a location that is fairly docile in regards to oil movement, but that's a different story.
 
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Alex

Active Member
#8
i think my issue is the proximity of the exhaust - it hugs right ontop of the transaxle (a finger width clearance, not enough to do a heat shield) ... my exhaust is titanium and it's changed color from the liquid silver to rainbow hue by itself, so definitely hot.

I'd like to position my catch can where it fills from the bottom and then drains back in, but the challenge is the only location that is viable would basically have it spewing onto the headers and onto the clutch (because of that open area on the 930 where you can see the clutch and flywheel) if it ever pushed out of the catch can somehow.

So I guess my safest best would be to run a hose straight up and then down into a catch can that I manually drain. I only drive it like 50 miles/yr, so it's not that much of a pain to do.
 

Jack

Bronze Supporter
#9
AN-6 line is plenty. Original vent is a little smaller than that. Upward, then down to a vented catch can with a drain spigot at the bottom.
You'll have to drill & tap the case for the fitting though. Use grease and go slowly, the grease will trap the shavings. IMO, of course. I've done similar with an inverted 930.
 

Alex

Active Member
#12
I pulled out the oem vent today ... kinda disappointing - I thought it was going to be some fancy setup with a ball valve or whatever and it's just a piece of pipe that necks down to a smaller size and then a straight shoot out the rear. not ball valve or anything
 

Randy V

Administrator
#13
I pulled out the oem vent today ... kinda disappointing - I thought it was going to be some fancy setup with a ball valve or whatever and it's just a piece of pipe that necks down to a smaller size and then a straight shoot out the rear. not ball valve or anything
Measure the diameter of the threads top and bottom to see if tapered (pipe) or not.
My G50 was not. It required an ORB fitting as I recall..
 

Jac Mac

Active Member
#14
If its non - inverted & in your SLC then you must have flipped the Ring of the R&P to have correct direction in which case the lube getting thrown off R&P is likely to aim at that fitting... I assume fitting above R&P in attached pic is what your on about.
 

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Alex

Active Member
#15
Measure the diameter of the threads top and bottom to see if tapered (pipe) or not.
My G50 was not. It required an ORB fitting as I recall..
it's definitely not o-ring. CMS told me m14x1.5 ... I screwed one in and it went in properly, so I'm pretty sure that's the right size.


If its non - inverted & in your SLC then you must have flipped the Ring of the R&P to have correct direction in which case the lube getting thrown off R&P is likely to aim at that fitting... I assume fitting above R&P in attached pic is what your on about.
yes, that's the vent fitting. my r&p was flipped
 

Jac Mac

Active Member
#16
it's definitely not o-ring. CMS told me m14x1.5 ... I screwed one in and it went in properly, so I'm pretty sure that's the right size.
yes, that's the vent fitting. my r&p was flipped
Right, then you need to modify that fitting so that the hole or tube extending into the trans is pointed toward the right and forward. If you imagine the nose of car is North/tail South then it should point NE. That should ensure oil thrown from R&P wont enter fitting.
 

Alex

Active Member
#17
Right, then you need to modify that fitting so that the hole or tube extending into the trans is pointed toward the right and forward. If you imagine the nose of car is North/tail South then it should point NE. That should ensure oil thrown from R&P wont enter fitting.
that would have it poisitioned right at the clutch & headers ... not ideal if it decides to burp fluid :/

i don't think there's anything wrong with my current plan - run a -6 line straight up and then down into a vented catch can?

now that I see it's the flipped r&p slgining fluid that's causing the issue and not the transaxle venting fluid for an unknown reason, I shouldn't find anything in the can....
 
#18
Hi, in my inverted race application, I have a Moroso catch can (with top mounted breather) receiving oil puked from the top of the trans that is directed into the top side of the can. This drains directly back to the trans from the bottom of the can through a modified fitting in place of the filler plug on the side of the trans. Obviously the can sits above the trans. Until i installed the drain-back, the catch can would overflow in race conditions. As Jac has mentioned, the vent is prone to oil slung off the ring in inverted situations. Cheers, Andrew
 

Jac Mac

Active Member
#19
It gets slung off the Ring Gear toward that vent anytime its fitted with mid engine/trans at rear in both standard & inverted applications, any difference would be the oil level which is usually lower in the inverted application. The BEST cure would be to block that fitting and place the vent in an area of the case where there is minimal oil spray/surge etc.
 

Alex

Active Member
#20
It gets slung off the Ring Gear toward that vent anytime its fitted with mid engine/trans at rear in both standard & inverted applications, any difference would be the oil level which is usually lower in the inverted application. The BEST cure would be to block that fitting and place the vent in an area of the case where there is minimal oil spray/surge etc.
unfortunately some of us arn't brave enough to poke holes in our transaxle :stunned:

I'll have to settle for next best alternative - -6 hose that goes up, then down to a vented can.
 
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