Gearbox inversion - Precisely!
Discussion
Like many of us here building our (hopefully) precious monsters, and not being experts in any one element of the build, we rely on others to give a helping hand or advice...
....which often freely given and priceless. I thank you all!
Now to the point...
Oft brought up I know and that is the choice of Gearbox, suitability and its various mods and usage.
..And there appears to be many opinions out there, and is a well worn subject on this site, however my question is all about inversion.
Once we have plumped for a gearbox (I for one the GT2 6 speed box - for better or worse), which is not an inconsiderable cost, greater or lesser, depending on its exotic qualities, we naturally want to protect this investment from as much premature wear/ failure as we can. On this point, and since all these Porsche derivatives have to run un-naturally inverted with far more stress that they were originally built for, it seems that advice ranges from no mods at all, to a full rework of oilways and internal magic and black science to which I have no inkling!
Can anyone who has good experience and expertise out there settle this subject for us and recommend what in their opinion actually should be done in detail?
I for one would love to know, as I suspect others will!
Yours hopefully....
Keith
....which often freely given and priceless. I thank you all!Now to the point...
Oft brought up I know and that is the choice of Gearbox, suitability and its various mods and usage.
..And there appears to be many opinions out there, and is a well worn subject on this site, however my question is all about inversion.
Once we have plumped for a gearbox (I for one the GT2 6 speed box - for better or worse), which is not an inconsiderable cost, greater or lesser, depending on its exotic qualities, we naturally want to protect this investment from as much premature wear/ failure as we can. On this point, and since all these Porsche derivatives have to run un-naturally inverted with far more stress that they were originally built for, it seems that advice ranges from no mods at all, to a full rework of oilways and internal magic and black science to which I have no inkling!
Can anyone who has good experience and expertise out there settle this subject for us and recommend what in their opinion actually should be done in detail?
I for one would love to know, as I suspect others will!
Yours hopefully....
Keith
Well, I'm definitely not an expert at all, and am more than happy to stand corrected, but I'm pretty sure that (at least some of) the Porsche gearboxes were derived from the 956/962 racers, which of course were mid-engined. So the development of these for the 911 meant the box was inverted for the rear engine layout. I have read this somewhere, possible via the Ultima forum (Stig's build site perhaps?) so in theory the inverted gearbox should be fine.
I'm sure an expert will be along in a minute!
I'm sure an expert will be along in a minute!
I have just had my 996 box back from GBOX in the states, after having it reworked. ( see my thread 'My Box is back!)
They advised that as the box will be running inverted that the oil ways need to be adjusted / modified accordingly. They believe that that if the oil ways were designed for one orientation it makes sense to ensure that the oil gets to where it is required when the box is placed in a different orientation i.e. inverted.
By doing this modification I now have a proper oil filler whole and not a small whole where the original breather was and I do not now need a breather and associated tank (however I may still fit one, just to be sure).
I am sure there will be different opinions but for what it's worth this is the one from GBOX.
David
They advised that as the box will be running inverted that the oil ways need to be adjusted / modified accordingly. They believe that that if the oil ways were designed for one orientation it makes sense to ensure that the oil gets to where it is required when the box is placed in a different orientation i.e. inverted.
By doing this modification I now have a proper oil filler whole and not a small whole where the original breather was and I do not now need a breather and associated tank (however I may still fit one, just to be sure).
I am sure there will be different opinions but for what it's worth this is the one from GBOX.
David
I know it was always roumoured that the older version of the porsche box that was designed to run inverted, but its not confirmed and it certainly doesnt apply to current boxs... I dont know about the std 996 box but the G50 and the GT2/3 boxs have an issue with 3rd gear not getting oil when its inverted... to get over this you need to overfill the box or modify the oildways to spray the gears.
Now almost all Ultimas out there just have the box inverted and overfilled with a simple mod to the breather... this works perfectly well and has proved very reliable, its what I did in my canam and I abused that at the strip etc and its still going 5 years later.
Its not optimum though as it does produce additional drag losses that additionally heat the oil (thus it strongly recomended you dont panel under the engine of gearbox to help cool the box)... so you loose some wheel HP and the gearbox runs hotter.
So the optiumm thing to do is add in spray bars to the box and not overfil it and maybe add an oil cooler.... but its not a must do in the same was as fitting a winged sump with accusump etc.
PS
Want to make it clear, Im not an expert on porsche boxs and this is purelly knowledge I have gleamed from the research I have done for my car.
Now almost all Ultimas out there just have the box inverted and overfilled with a simple mod to the breather... this works perfectly well and has proved very reliable, its what I did in my canam and I abused that at the strip etc and its still going 5 years later.
Its not optimum though as it does produce additional drag losses that additionally heat the oil (thus it strongly recomended you dont panel under the engine of gearbox to help cool the box)... so you loose some wheel HP and the gearbox runs hotter.
So the optiumm thing to do is add in spray bars to the box and not overfil it and maybe add an oil cooler.... but its not a must do in the same was as fitting a winged sump with accusump etc.
PS
Want to make it clear, Im not an expert on porsche boxs and this is purelly knowledge I have gleamed from the research I have done for my car.
Keith, Sorry I do not have the specifics but if you talk to Josh at GBOX I am sure he will give you the information.
For completeness GBOX details:
5757 Arapahoe Ave.
Unit C1 East
Boulder, Colorado 80303
Phone: 303.440.8899
Fax: 303.440.0994
And just in case your thinking, no I am not on commission !!
David
For completeness GBOX details:
5757 Arapahoe Ave.
Unit C1 East
Boulder, Colorado 80303
Phone: 303.440.8899
Fax: 303.440.0994
And just in case your thinking, no I am not on commission !!
David
(Sigh!)
You see...
..the situation is far from clear-cut...
...The factory bless-them, have already suggested my choice of box is not recommended
, so asking them for advice on the oiling is somewhat superfluous.
The third-gear thing is useful to know...
Pity I don't live in the states as GBOX would be worth talking to, but I don't.
Not sure who in the UK?
Then there is the sticky subject in whether the advice I would be getting is somewhate bias towards spending dosh I can ill-afford on a mod that actually does nothing to enhance longlevity. I have no problem contributing to someones profits, provided their service is beneficial to me in equal proportion.
More comments please!
cheers
You see...
..the situation is far from clear-cut...
...The factory bless-them, have already suggested my choice of box is not recommended
, so asking them for advice on the oiling is somewhat superfluous. The third-gear thing is useful to know...
Pity I don't live in the states as GBOX would be worth talking to, but I don't.
Not sure who in the UK?
Then there is the sticky subject in whether the advice I would be getting is somewhate bias towards spending dosh I can ill-afford on a mod that actually does nothing to enhance longlevity. I have no problem contributing to someones profits, provided their service is beneficial to me in equal proportion.
More comments please!
cheers
Keith, phoning GBOX in the States is no big deal, in fact I wouldn't mind betting that they would phone you back if you left a message in their voice mail, or drop them a mail, that's how I first got in touch. Their customer service is very good (something other company's could learn from!), and their knowledge of Porsche box's second to none.
Captain Slog said:
I would take Stigs' comments as a benchmark, before I would splash out any hard earned coin I would want to know if its a known problem, are boxes continuously failing ?, I seem to have seen very few threads about Boxes failing in an Ultima
That was the point I was making. Not sure I can ever remember a box failing in fact?As you correctly point out, gearbox specialists are in the business of recommending modifications. They may not be necessary at all.
Still no harm in doing some research into it I guess
Edited by Stig on Thursday 11th September 12:36
There are plenty that have failed (graham Ps in last few mths).... but these are usually the weaker std 996 box not the G50's.... and I dont think these failures are down to the inversion!
The GT2/3 box is just a certain G50 (biggest diff one) with a different casing to change it to cable shift and make gear changes easier.... The G50's are pretty much bullit proof... and if your looking to increase reliability then I'd save your cash and just do what everyone else does and overfill it with a good breather kit.
I know Ian E modified the G50 for spray bar himself... not spoken to him for a while or seen him on here but I have some pics I took of his when it was on the bench.
The GT2/3 box is just a certain G50 (biggest diff one) with a different casing to change it to cable shift and make gear changes easier.... The G50's are pretty much bullit proof... and if your looking to increase reliability then I'd save your cash and just do what everyone else does and overfill it with a good breather kit.
I know Ian E modified the G50 for spray bar himself... not spoken to him for a while or seen him on here but I have some pics I took of his when it was on the bench.
andygtt said:
There are plenty that have failed (graham Ps in last few mths).... but these are usually the weaker std 996 box not the G50's.... and I dont think these failures are down to the inversion!
The GT2/3 box is just a certain G50 (biggest diff one) with a different casing to change it to cable shift and make gear changes easier.... The G50's are pretty much bullit proof... and if your looking to increase reliability then I'd save your cash and just do what everyone else does and overfill it with a good breather kit.
I know Ian E modified the G50 for spray bar himself... not spoken to him for a while or seen him on here but I have some pics I took of his when it was on the bench.
Oops - I'd forgotten about Graham's. Still, I can't recall any others!?!? Certainly not 'plenty' Andy?The GT2/3 box is just a certain G50 (biggest diff one) with a different casing to change it to cable shift and make gear changes easier.... The G50's are pretty much bullit proof... and if your looking to increase reliability then I'd save your cash and just do what everyone else does and overfill it with a good breather kit.
I know Ian E modified the G50 for spray bar himself... not spoken to him for a while or seen him on here but I have some pics I took of his when it was on the bench.
Surely overfilling it is just going to fill the breather catch tank and then spray oil all over the engine bay!??
Re. the GT2 box - that has a pawl-type-diff doesn't it? I recall reading a report where it was fitted to a Lola T70 that said that if you lifted off mid corner the tail got loose VERY suddenly, then when you loaded it up again the front pushes alot
Edited by Stig on Thursday 11th September 13:47
Stig said:
Still, I can't recall any others!?!?
"14 FC"s G50/03 had to be rebuilt after losing 2nd/3rd gear. This gearbox had completed the Powertour and was used as a demonstrator at the Donnington show. After it was rebuilt, I bought it (the gearbox) off the factory and it has been working fine for 6 years. It is possible to break almost any gearbox if you try, that is not to say the gearbox isn't up to the job. In my case I think I'd take the risk of a rebuild and use a stock gearbox, before paying £2.5k for a modification that might not be needed. But I am running an AS 540 engine, so maybe those with more torque might choose some modification. I assume that the people that are modifying their gearbox are also uprating their driveshafts, as there is more evidence (IMHO) that they are the weak link in the chain.
It is also worth noting that standard road tyres will also reduce the torque load on the gearbox (as they will slip first). Not withstanding shock loads from an aggressive style.
YIIHAA said:
Stig said:
Still, I can't recall any others!?!?
"14 FC"s G50/03 had to be rebuilt after losing 2nd/3rd gear. This gearbox had completed the Powertour and was used as a demonstrator at the Donnington show. After it was rebuilt, I bought it (the gearbox) off the factory and it has been working fine for 6 years. It is possible to break almost any gearbox if you try, that is not to say the gearbox isn't up to the job. In my case I think I'd take the risk of a rebuild and use a stock gearbox, before paying £2.5k for a modification that might not be needed. But I am running an AS 540 engine, so maybe those with more torque might choose some modification. I assume that the people that are modifying their gearbox are also uprating their driveshafts, as there is more evidence (IMHO) that they are the weak link in the chain.
It is also worth noting that standard road tyres will also reduce the torque load on the gearbox (as they will slip first). Not withstanding shock loads from an aggressive style.
Am I right in thinking the modifications being discussed here are related just to oil spray?
If so, then I would have to say that these will add longevity to the 'box but will give very little help in improving the amount of torque the 'box can handle.
As the mods will cost as much a a replacement box I would favour waiting until I had broken my first 'box.
Steve
If so, then I would have to say that these will add longevity to the 'box but will give very little help in improving the amount of torque the 'box can handle.
As the mods will cost as much a a replacement box I would favour waiting until I had broken my first 'box.
Steve
Sorry if I lead everyone to believe that it cost £2600 just to do the inversion, the £2600 that GBOX charged included ;
Labour to repair
Safety Wire
Driveline Assy Case Sealant
Machine shop time to modify ( incl. Inversion)
The inversion of the box and the reworking of all of the oil passages associated with this mod.
Replacement parts:
1off Main Angular contact bearing
1off Pinion bearing
1off 2nd Gear Idler
6off Shift Shaft Spiral Clamp pins
1st/2nd Shift Sleeve Assy.
3rd/4th Shift Sleeve Assy.
3off 3rd/4th/5th/6th Synchro Rings
2off Shift Rings
2 off Synchro Cone Ring
2 off Synchro Rings
2off Diff Side Seals
1 off Main Oil Seal
Media Blasting and Powder Coating
All this for less than £2600.00
Hope this puts it into perspective.
David
Labour to repair
Safety Wire
Driveline Assy Case Sealant
Machine shop time to modify ( incl. Inversion)
The inversion of the box and the reworking of all of the oil passages associated with this mod.
Replacement parts:
1off Main Angular contact bearing
1off Pinion bearing
1off 2nd Gear Idler
6off Shift Shaft Spiral Clamp pins
1st/2nd Shift Sleeve Assy.
3rd/4th Shift Sleeve Assy.
3off 3rd/4th/5th/6th Synchro Rings
2off Shift Rings
2 off Synchro Cone Ring
2 off Synchro Rings
2off Diff Side Seals
1 off Main Oil Seal
Media Blasting and Powder Coating
All this for less than £2600.00
Hope this puts it into perspective.
David
Stig said:
Oops - I'd forgotten about Graham's. Still, I can't recall any others!?!? Certainly not 'plenty' Andy?
Surely overfilling it is just going to fill the breather catch tank and then spray oil all over the engine bay!??
Re. the GT2 box - that has a pawl-type-diff doesn't it? I recall reading a report where it was fitted to a Lola T70 that said that if you lifted off mid corner the tail got loose VERY suddenly, then when you loaded it up again the front pushes alot
Wasnt saying its the norm but I know of plenty... certaily more than a few and they were hardly a secret.Surely overfilling it is just going to fill the breather catch tank and then spray oil all over the engine bay!??
Re. the GT2 box - that has a pawl-type-diff doesn't it? I recall reading a report where it was fitted to a Lola T70 that said that if you lifted off mid corner the tail got loose VERY suddenly, then when you loaded it up again the front pushes alot
But who cares, point is they are durable and reliable. not sure what you mean about overfilling, are you saying you did not overfil your boxs by the amount the factory recomend?
Not worried about the GT2 diff as I am using only the gears and CWP from my GT2 box and swoping them into my GT3 cup racer box which is already modifed to suit a 1100kgs car.
So I guess all these posts prove the OP's point... that there is a lot of conflicting advice in this area and no real clarification.
All I know is that if I have the spare cash at the end of the build I will be fitting spray rails a pump and a cooler on my box.... if the cash has run out I will simply fit a normal inverted breather kit.
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