901 or 915 gearbox

[Fishcop]

Ditto Cam's advice. The closer you get to how Porsche built it, the better/more desirable the car will be in the future. And if you end up on a path to full-blown restoration sickness, you're one more step closer.

Why on god's earth you'd jemmy a G50 onto the back of a vintage 911 engine is beyond me.

The 901/911 boxes are exactly what they're meant to be. Super simple to work on and you can comfortably rebuild one in your garage over a weekend. They can be strengthened, ratios changed, Group Sb cars race with them - and as far as I can recall, no one has blown a 901 through normal use (over-rev engine damage has occurred, but not just with 901 boxes ). The "weakness" is a cantilevered 1st gear, and once again I know of no one who has managed to damage first in a road oriented car or even a 2.0 race car.

For the record I have a fully sorted 915 in my 69 that is like butter to use. Those that have driven it will agree it is nearly like driving a Corolla box But there is $8k in it with all new synchros, Wevo internals - shifter - PSJ- and Wevo/AP clutch.

[Bremith]

Yes the 901/11 is ok and the sensible option in this case. But the G50 series is a much, much better box, (which is why it is used in so many non Porsche applications), folks like Patrick make bolt in kits (no jemmying required) and by the time you buy a 901/11 box and rebuild it with all the trick gubbins from wevo etc to make a 901/11 box work better, it would interesting to see how it matches up cost wise to a G50, the only downside to which (apart from it not being "period") is it is a bit heavier, by a quarter of a tank of petroleum. But unless you do something really, really (really) stupid with it, it will last forever, and work like new the whole time.

[Fishcop]

Ash's question was 901 or 915 specific... And now we've introduced the G50?

Yes the G50 is a good box, and it's used in a whole lot of other applications - for 400+ HP. Porsche purposely brought it in at the end of the G series era to dial up it for the forthcoming 3.6 964 and other forecast models. The other thing that makes the G50 'special' is it is actually a ZF based unit and uses superior synchronising. Porsche's 901/915 "energiser" bands are indeed antiquated and destined to wear quicker than the systems we see in Asian and later Euros. But they do last 200k comfortably when driven as meant in road oriented conditions.

Another reason the G50 box is popular in other applications is that it the diff can be 'flipped', or the entire transmission can be installed and plumbed inverted so it becomes a mid-engined transaxle, pretty cool.

The cost of putting a G50 into an early chassis matched to any engine from the era just because it's stronger is fiscally stupid and mechanically pointless. To get a shortened G50 made or to cut up an early chassis is going to cost far more than using a professionally rebuilt (or otherwise) 901/911 or 915 gearbox with upgrades (and only if needed).

Think we're muddying the water for Ash over a modification that no one would recommend for an early 911.

[Bremith]

Ummm...I only referred to G50 because Ash mentioned in his first post, so if he's expecting G50 shift, reliability etc he simply won't get it from a 901/15, no matter how many aftermarket bits you throw at it because, frankly, they're not very good gearboxes, only partly because they continued using Porsche synchromesh long after the rest of the industry moved on to better things. No it wasn't around in 1971, but neither was a 915, so a 915 in a car that originally had a 90X sporto wd be no more correct than a G50. The fact they are such a good gearboxes that they will easily handle 964 power and torque is hardly an argument that rules them out. I would be interested in the cost of buying a 901 box and then rebuilding vs installing a G50 kit. Be surprise if there was much of a cost penalty, so the only difference is originality. And minor weight difference.
But like I have said Ash, sounds like 901 for you.
All other things being equal, the G50 is a much, much better box. If anyone can find me someone who took a G50 out to put in a 901/11/15 with a cable operated clutch because it is better, cheaper or lighter I will be very, very Impressed.
Back to you Ash.

[Fishcop]

Yeah I'm lost now Mitchell. You're right, Ash referred to the G50 off the bat. And I didn't set out to pick a fight

I never argued you'd rule out putting a G50 into an early chassis because it was a good box and could handle power. I personally rule it out because it simply doesn't fit in a 911 chassis from 64 to 86. That's the best answer to the question.

A missing 905 sporto may well make Ash's car incorrect, but Porsche designed the car to also take the 901/911 manual.

The cost of changing the torque tube and pick ups, and the sourcing of a 2 year only TT and TBs, a G50/00 box (and reconditioning it - because it's 29 years old) would be seriously expensive. However, sourcing a G50, reconditioning it, machine work and shortening conversion, supporting cross member, and the flywheel/clutch has me conservatively thinking $12-15k.

A 901, or more accurately a 911 box can be found readily in the USA (if not here of course). Reconditioning it to factory specs and delivering it to Australia would be around $6k. The same 915 I think would run $8k.

You are also completely correct that no sane person would remove a G50 from a 87-89 Carrera and replace it with a 915.

I love that you love the G50. It's a great box and I've loved driving G50 cars. That you consider the 901/915 "frankly not very good" is interesting considering the longevity, racing providence, and overwhelming success of the transmissions over a joint 22 year production cycle and the 30 years since the production of the latest ended.

Let us know how you go Ash

[Ashbaxter]

wow that escalated quickly

Thanks for all of the insights guys I am getting the 915 rebuilt anyway and may have the option to swap for a 901 so I'll let you know what I end up with

[Bremith]

Cheers Ash.

For anyone else out there interested in understanding the full range of gearbox options for an early LWB pre 1987 911 it's worth looking at the Patrick Motorsport website as conversions like theirs (and there are others) are entirely bolt in and completely reversible and do not require modifications to torque tubes etc.

[Lyndon]

Hi Mitchell. I would be interested in seeing someone who has tried to install a G50 into an early car. Especially a pre 71 901. I think that would be impossible without some major mods. I know people who have put G50s into mid 70s cars and even with the short bell housing (25mm reduced I think) it still requires some small mods to fit. The end housing, even the small ended G50/00 is much larger than a 915. If you have seen the 2 side by side they are massively different. Guess its buyer be ware, people say many things to sell product.

[Cairns888]

I loved my 901 box. Could not ask for anything more.
It shifted as good as I could ever want. I didn't even have a short shift. It made it a lot of fun on the twisty roads and I think it took way more for skill to be able to throw your car through there and make all the gear changes bang on whilst on the absolute limit.

Maybe a G50 is a nice box but it is like putting a 3.0 fuel injected engine in a SWB. It might make you feel warm and fuzzy inside but you just don't get it.

[mrar]

Drove 901 Gbox today, they are a fun alternative to the standard style shift pattern. Thumbs up

[Bremith]

Ok I am now suitably personally "forum chastened" for pointing out the obvious that the G50 is a lot better gearbox in every respect than the 901/11 and 915 (as almost anyone who fixes Porsche gearboxes for a living will tell you) and yes you can put one in a LWB 911. Yes they are heavier (10-15kgs) and bigger and it will cost a lot. My understanding is they can go in a LWB without chassis molestation, I will check and report back for the record.

I think I should be free to point this out in the same way people should be free to enjoy whatever gearbox they like, and put fuel injected 3.0s in SWB cars if that floats their boats. Each to their own. It doesn't mean they "don't get it".

The reason I know a bit about it is because I researched options for a 911 rally car. Gearboxes are free in the Oz classic class as long as they are H pattern (not sequential) and have no more than 5 speeds. Rallying is about as tough on a gearbox as you can get. Yes people run 901/11/15s in rally cars but primarily because they are not allowed to run anything else in the particular class.

Whether an individual wants/needs a G50 is an entirely acceptable personal choice, but it is definitely an option.

[Merv]

True Mitchell. If you drive a car hard every other day and put it under constant strain or if you put 500hp on top of it, the G50 is the box of choice.

However, for most who drive their early cars less than daily and not under race conditions, it would seem in the 'sledge hammer' category. I think Vic Elford won the 68 Monte with a 901 'box?

[ELSPORTO]

Did I mention I'm still on the look out for a 901 if anyone has one lying around.

[Cairns888]

Don't feel beaten up Mitchell. I understand what you are trying to say 100%. My view is that if you put a G50 in why not go for another gearbox out of another car. I am sure if you look hard enough you find something that not only fits but it will be cheaper and stronger. Maybe I am wrong though.
Maybe another forum thread is due to see if there is any boxes that can be modded to suit early cars?

This is a 901 v 915 debate. If they were absolutely garbage gearboxes then I see no reason to fix something else. But they are not.

Enjoy your day and get that "S" back on the road so we can blow up some gearboxes!

[JulianG]

http://www.early911sregistry.org/forums/showthread.php?120321-901-Close-Ratio-Gearbox

Did I mention I'm still on the look out for a 901 if anyone has one lying around.