Does anybody have any info on running the G50 transaxle inverted for a mid engine application? My big concern is oiling. I have a chance to buy one, but would like some more info first. Cheers, Dave
Porsche G50 gearbox-inverted
- Thread starter Dave Decker
- Start date
Dave
That's a standard application for mid engine replicas.
Kennedy Engineered Products among others sells
the adapter pieces. Oiling not a problem.
MikeD
That's a standard application for mid engine replicas.
Kennedy Engineered Products among others sells
the adapter pieces. Oiling not a problem.
MikeD
Oiling..
I have seen applications where people go to lots of trouble to add oil pumps and lines to feed oil to areas of the transaxle. I have worked on many industrial and truck gear drive units and in my opinion, as long as oil is touching the bottom of the gears it will through it everywhere. Just make a new oil level, so it is a little higher, big deal. Make sure the 'new' top (which was the bottom) has a vent or the oil seals will want to leak.
Jim
I have seen applications where people go to lots of trouble to add oil pumps and lines to feed oil to areas of the transaxle. I have worked on many industrial and truck gear drive units and in my opinion, as long as oil is touching the bottom of the gears it will through it everywhere. Just make a new oil level, so it is a little higher, big deal. Make sure the 'new' top (which was the bottom) has a vent or the oil seals will want to leak.
Jim
Thanks for the responses guys. The guy with the transaxle has already addressed the vent-fill plug issue. This is the transaxle that was on ebay a bit ago. I'm encountering some difficulty prying my wallet open! Cheers, Dave
Hi Corvairdave,
I have details and pictures of G50 Inverted in one of my Ultimas , I have no special pumps but remember the following:
The filler plug is now the drain plug
The breather hoses I used need a small modification to a plug.
The slave cylinder will be at the bottom , so clearance is required.
The G50 mounts at the rear via a dounut, unless others have different ideas !
Drive shaft outlets will be higher than say a renault, watch chassis clearances.
Use the correct oil and quantities.I have never had a single box problem and I push it hard.
I currently am fitting a G50 into a GTD chassis, it's going well and I cant see any problems occuring. The G50 will handle the 640 BHP i'm putting in it.
I have details and pictures of G50 Inverted in one of my Ultimas , I have no special pumps but remember the following:
The filler plug is now the drain plug
The breather hoses I used need a small modification to a plug.
The slave cylinder will be at the bottom , so clearance is required.
The G50 mounts at the rear via a dounut, unless others have different ideas !
Drive shaft outlets will be higher than say a renault, watch chassis clearances.
Use the correct oil and quantities.I have never had a single box problem and I push it hard.
I currently am fitting a G50 into a GTD chassis, it's going well and I cant see any problems occuring. The G50 will handle the 640 BHP i'm putting in it.
Bringing this back to the top to see if anyone has accumulated an appreciable number of miles (thousands) with an inverted G50 Trans.
The input and mainshaft will be fine with running submerged as long as their seals are in good shape - the only thing I would be concerned with it the counter gear / shaft and bearings. Not having had a G50 apart - I can't speak to how they are designed. I've been through many dozens of other standard transmissions and they typically have either bronze oil-light bushings or needle bearings in them. These are designed to be run submerged to give them a constant supply of lube.
I'm thinking that I would probably need to run the gearbox a little over it's normal capacity to ensure adequate lubrication and cooling of the counter gear / shaft..
Thanks!
The input and mainshaft will be fine with running submerged as long as their seals are in good shape - the only thing I would be concerned with it the counter gear / shaft and bearings. Not having had a G50 apart - I can't speak to how they are designed. I've been through many dozens of other standard transmissions and they typically have either bronze oil-light bushings or needle bearings in them. These are designed to be run submerged to give them a constant supply of lube.
I'm thinking that I would probably need to run the gearbox a little over it's normal capacity to ensure adequate lubrication and cooling of the counter gear / shaft..
Thanks!
Fran Hall RCR
GT40s Sponsor
This spray bar mod. is absolutely NOT necessary in normal use ......only in extremely high HP or race type applications...but a higher oil level should be run to keep gear faces/surfaces lubricated....hence the reason for a good input shaft seal.
Bill D said:
Yep - that's already in the works.. What my concern is though is the bearings hidden inside the countergear assembly..
Here's a representative image of the type of needle bearings I'm talking about;
((note - these are not pictures of a Porsche gearbox))
Pete McCluskey.
Lifetime Supporter
Big foot, I have done 8,000 klm's with an inverted G50, about 4000 miles
no problems at all.
no problems at all.
Normally (running uninverted) there is some extra space in the bottom of the trans housings for a larger pool of gear oil. When inverted, that changes, since clearance up top was minimal to begin with, so now it doesn't hold much oil. What happens now is that the gears of the input shaft will be largely submerged, perhaps entirely. If you run the "same" oil level as before, or higher, you will probably submerge the pinion shaft & gears as well. So there could just be some friction losses for the gearteeth slogging through thick oil.
What determines the "same" oil level is an interesting question. "Normally" the correct level is 5mm below the oil filler opening. When inverted, that specification is meaningless. Uninverted that equates to roughly 3 liters.
Note that despite what appeared earlier in an otherwise excellent reply, the filler plug does not become the drain plug. The filler (on the side) is still the filler, but the drain is now the breather, and the old breather is now the drain. Terminology I suppose, since you could in theory remove the breather when uninverted to fill it, it's just that you can't get at it in a 911, nor is there any reason to when the 'real' filler is on the side, and more importantly, the correct level was being determined by taking a reading there during filling. A lot of shops fill them to the point of overflow, which is incorrect, and can cause annoyances.
What determines the "same" oil level is an interesting question. "Normally" the correct level is 5mm below the oil filler opening. When inverted, that specification is meaningless. Uninverted that equates to roughly 3 liters.
Note that despite what appeared earlier in an otherwise excellent reply, the filler plug does not become the drain plug. The filler (on the side) is still the filler, but the drain is now the breather, and the old breather is now the drain. Terminology I suppose, since you could in theory remove the breather when uninverted to fill it, it's just that you can't get at it in a 911, nor is there any reason to when the 'real' filler is on the side, and more importantly, the correct level was being determined by taking a reading there during filling. A lot of shops fill them to the point of overflow, which is incorrect, and can cause annoyances.
Lynn Larsen
Lynn Larsen
As to the fill hole, I agree with your terminology JM, some have gone as far as drilling a new fill hole at one of the webbing crosses. I saw no good reason to drill another hole in a perfectly good transaxle case. I simply made an L shaped dipstick and, as I filled the transaxle with specified amount of lube, marked the dipstick at the 1 pt. from full and full marks. The measurement is made with the dipstick resting on the lower threads of the existing fill hole. As I did this the first time, I made certain that the oil level was at least level with input shaft; as mentioned, it is actually just above it. (The real issue with fill level is that enough oil gets up on the pinion and into the diff more than the gear sets themselves. Some have even suggested that the proper way to fill an inverted Porsche transaxle is to loosen one of the output flanges and fill until oil leaks out around it.)
Bigfoot, DRB/GT40 Australia cars have been running inverted G50s for years (probably getting close to 10 now) with no problems other than the input shaft seal leaking (possibly) prematurely because of being submerged. Lesson here is, if you have the transaxle out and it has significant time on it, replace the seal - it is not a difficult task.
Bigfoot, DRB/GT40 Australia cars have been running inverted G50s for years (probably getting close to 10 now) with no problems other than the input shaft seal leaking (possibly) prematurely because of being submerged. Lesson here is, if you have the transaxle out and it has significant time on it, replace the seal - it is not a difficult task.
A basic way of achieving the correct level would be with the box in its designed for position, to draw a theoretical horizontal line from the bottom of level bung hole accross to the output drive flanges (90' to the bellhousing face), measure the distance between this line and the centre of the drive flange.
Invert the box, apply the same measurement now from the centre of the flange, on its other side up the box. Draw a line back towards the level bung.
This gives you the level that the diff bearings an pinion need the oil level to be set to.
If its below the current filler bung level make up a little piece of welding rod or old dipstick to go inside the filler bung for checking.
Read this 3 times now,
still cant think of an easier way of explaining it.............
Invert the box, apply the same measurement now from the centre of the flange, on its other side up the box. Draw a line back towards the level bung.
This gives you the level that the diff bearings an pinion need the oil level to be set to.
If its below the current filler bung level make up a little piece of welding rod or old dipstick to go inside the filler bung for checking.
Read this 3 times now,
still cant think of an easier way of explaining it.............llarsen said:
IMHO this is a rapidly spreading urban myth. If oil is leaking it is because the seal is faulty, not because it is submerged. If the trans is in the normal Porsche position, when driving EVERYTHING inside is covered and splattered in oil, with a faulty seal it may not leak out when standing still but certainly will when being driven.
Never the less I agree the seal (all seals actually) should be carefully inspected and renewed if necessary while the trans is out.
Just my 2c
Cheers
Actually that is good explanation Joe. I guess what I was getting at, is that the original or uninverted fill level is just below the pinion shaft. Now we're going to be above the input shaft. That's all I'm saying. Obviously it's not a big problem.
Re: the seals, very good point. In the 911 the G50 shift rod seal is notorious for leaking (when parked). But then that is because people run them 100k miles or 50k and track use, and 10 to 20 years. These are reasonable change intervals, and as you said it is not all that tough to do.
Re: the seals, very good point. In the 911 the G50 shift rod seal is notorious for leaking (when parked). But then that is because people run them 100k miles or 50k and track use, and 10 to 20 years. These are reasonable change intervals, and as you said it is not all that tough to do.
Lynn Larsen
Lynn Larsen
Russ,
I don't disagree and that is exactly why I said (possibly) ;-) Sometimes it's easier to conceed an outside chance than argue the point; and then, point out that there is an easy remedy if someone is worried about it. For myself, if it starts leaking, I'll fix it.
Lynn
I don't disagree and that is exactly why I said (possibly) ;-) Sometimes it's easier to conceed an outside chance than argue the point; and then, point out that there is an easy remedy if someone is worried about it. For myself, if it starts leaking, I'll fix it.
Lynn
Thanks for the input on this guys.. It's good to hear that there are gearboxes out there thay seem to have suffered no ill effects..
Seals - There are multiple types of seals on the market. For the sake of brevity - I'll focus on rotary oil seals rather than linear seals.
1) Pressure retention
2) Double-seal submerged (typical rear main seals)
3) Double-Seal low tension (typical front seal - also generally used with a slinger)
4) Single-Seal low tension (typical trans input shaft seal - also generally used with a slinger)
Suffice it to say - most input shaft seals would fall into the Type-4 area. It's not that they are not capable of holding back the lubricant - just that they are being made to perform outside the parameters they were designed for.
Back to the transmission itself;
Does anyone know if the G50 counter-gear-set has a hole in it to allow additional flow of lube?
Take a look at this Muncie 4 speed counter gear for reference;
Thanks!
Seals - There are multiple types of seals on the market. For the sake of brevity - I'll focus on rotary oil seals rather than linear seals.
1) Pressure retention
2) Double-seal submerged (typical rear main seals)
3) Double-Seal low tension (typical front seal - also generally used with a slinger)
4) Single-Seal low tension (typical trans input shaft seal - also generally used with a slinger)
Suffice it to say - most input shaft seals would fall into the Type-4 area. It's not that they are not capable of holding back the lubricant - just that they are being made to perform outside the parameters they were designed for.
Back to the transmission itself;
Does anyone know if the G50 counter-gear-set has a hole in it to allow additional flow of lube?
Take a look at this Muncie 4 speed counter gear for reference;
Thanks!
Maybe their are some options on the input shaft seal? perhaps a race application one built to type 2 spec double seal etc. Could a seal company produce these?
Does this raise the question of oil viscosity, is a thinner synthetic likely to squeeze past the seal?
On the gearset layout I have a schematic of a G50 type box, (more a G60)
Here Specialist Car - Web Links
It might give some clues to oilways.
This sort of highlights how an inverted box would hold a different amount of oil due to the casing design.
Does this raise the question of oil viscosity, is a thinner synthetic likely to squeeze past the seal?
On the gearset layout I have a schematic of a G50 type box, (more a G60)
Here Specialist Car - Web Links
It might give some clues to oilways.
This sort of highlights how an inverted box would hold a different amount of oil due to the casing design.
That schematic is actually the G64 all-wheel drive one (first model year 1989, ran through 1994). It has an unusual double pinion shaft, one inside another. It uses unique gears because the outer pinion shaft has a large diameter. I have a couple of these available if anyone wants to try something different. They can be converted to 2wd though the result is not a standard type.
Back to the schematic, it is close enough for this purpose. The oil filler is not shown, but the "normal" fill level would be just below the pinion shaft.
Back to the schematic, it is close enough for this purpose. The oil filler is not shown, but the "normal" fill level would be just below the pinion shaft.
I'm interested in converting a G64 to G50. Any help on how to fix the rotating shaft issue?
