Boxster S gearbox
Discussion
Hi All
I sold my Boxster S many years ago, always loved the gearbox... anyhow Ive been doing research into a project Im planning to build a mid engine car with a BMW V10 in the back and a porsche gearbox.
Now I have a 996GT3 cup racer box in the garage and a 996 GT2 box both of which would be great on the M5 engine... however they are big money boxes and I have them for other projects so would have to replace them....
In my research I have found someone putting the V10 in the back of a lotus exile and they have used a Boxster S gearbox... this gets me to the point as this box would be perfect for me, I know its a sweat gear change and its actually the right way up to start with (I have to invert the 911 gearboxes, not an issue but leave less room for sump) and its a much much cheaper box.
So how much torque has the Boxster S gearbox been reliable to... can it take 390ftlb and 500bhp at 8500rpm?... my booster S was 252bhp and similar torque seems a big jump but then Ive run 500ftlb in an old 4 speed 911 box made for a car with similar power to the booster S.
Any feedback or links would be appreciated
I sold my Boxster S many years ago, always loved the gearbox... anyhow Ive been doing research into a project Im planning to build a mid engine car with a BMW V10 in the back and a porsche gearbox.
Now I have a 996GT3 cup racer box in the garage and a 996 GT2 box both of which would be great on the M5 engine... however they are big money boxes and I have them for other projects so would have to replace them....
In my research I have found someone putting the V10 in the back of a lotus exile and they have used a Boxster S gearbox... this gets me to the point as this box would be perfect for me, I know its a sweat gear change and its actually the right way up to start with (I have to invert the 911 gearboxes, not an issue but leave less room for sump) and its a much much cheaper box.
So how much torque has the Boxster S gearbox been reliable to... can it take 390ftlb and 500bhp at 8500rpm?... my booster S was 252bhp and similar torque seems a big jump but then Ive run 500ftlb in an old 4 speed 911 box made for a car with similar power to the booster S.
Any feedback or links would be appreciated
I can't really comment on the transmission's ability to handle the extra torque but....
I run mine with Millers transmission fluid and the shift has been much smoother, especially when cold. As you may remember they are occasionaly a bit difficult until warm. I have 278lb/ft 290hp from mine so half of what you are planning. I also run a Carbonetic LSD, this made a great improvement to getting the power down and there are a few other LSD options now, when I did it, things like the Quaife were not yet available.
Renegade hybrids in the US are running LSx engines in the Boxster now and claim that the transmission can take it, I don't think they add any extra oil cooling or anything to make this happen. Maybe worth a call/email to them too?
I believe that the Audi 01E box is very similar/the same as the Boxster one and are even cheaper. I looked at using one of these for another mid engine project a while ago, might be worth a quick look
I run mine with Millers transmission fluid and the shift has been much smoother, especially when cold. As you may remember they are occasionaly a bit difficult until warm. I have 278lb/ft 290hp from mine so half of what you are planning. I also run a Carbonetic LSD, this made a great improvement to getting the power down and there are a few other LSD options now, when I did it, things like the Quaife were not yet available.
Renegade hybrids in the US are running LSx engines in the Boxster now and claim that the transmission can take it, I don't think they add any extra oil cooling or anything to make this happen. Maybe worth a call/email to them too?
I believe that the Audi 01E box is very similar/the same as the Boxster one and are even cheaper. I looked at using one of these for another mid engine project a while ago, might be worth a quick look
noone986s said:
I can't really comment on the transmission's ability to handle the extra torque but....
I run mine with Millers transmission fluid and the shift has been much smoother, especially when cold. As you may remember they are occasionaly a bit difficult until warm. I have 278lb/ft 290hp from mine so half of what you are planning. I also run a Carbonetic LSD, this made a great improvement to getting the power down and there are a few other LSD options now, when I did it, things like the Quaife were not yet available.
Renegade hybrids in the US are running LSx engines in the Boxster now and claim that the transmission can take it, I don't think they add any extra oil cooling or anything to make this happen. Maybe worth a call/email to them too?
I believe that the Audi 01E box is very similar/the same as the Boxster one and are even cheaper. I looked at using one of these for another mid engine project a while ago, might be worth a quick look
This is excellent information thanksI run mine with Millers transmission fluid and the shift has been much smoother, especially when cold. As you may remember they are occasionaly a bit difficult until warm. I have 278lb/ft 290hp from mine so half of what you are planning. I also run a Carbonetic LSD, this made a great improvement to getting the power down and there are a few other LSD options now, when I did it, things like the Quaife were not yet available.
Renegade hybrids in the US are running LSx engines in the Boxster now and claim that the transmission can take it, I don't think they add any extra oil cooling or anything to make this happen. Maybe worth a call/email to them too?
I believe that the Audi 01E box is very similar/the same as the Boxster one and are even cheaper. I looked at using one of these for another mid engine project a while ago, might be worth a quick look
If your running 278ftlb then you are only 100ftlb less than the 5L V10 engine as its the torque that would kill it... and if they are running LS engines on it now without issue then they are all running over 400flb so higher than what I will (amazed an LS would fit in a booster engine bay tbh)
All sounds like good news and shows this is certainly a very viable option.... not sure about the Audi option, quick search seemed that they were around £1k and the Boxster S ones are from £500 which is pretty much a bargain imo.
I have to say I think a 390 lb ft engine risks rapid destruction of any Boxster gearbox. Boxster is hardly a high torque car. Turbo 911s would be a much better comparison.
As for LS series engines, they are usually run with very robust transmissions indeed in GM applications. Corvette has a rear transaxle installation but it's probably too long for a mid-engine car. Additionally, in that application it is fitted with an oil cooler.
Like many modifications I'm sure that yours will work out fine so long as you keep a heavy right foot off the throttle pedal, especially in low gears.
In summary, high torque engines are enthusiastic in their appetite for eating under-specced transmissions. It's no accident that the big AMG cars are all automatics, where the computer can implement clever torque management to protect the transmission from an ape at the wheel! Same applies, of course, in Porsche PDK applications....
You could try to find out what Lotus were using in the back of their V8 Esprit but even that twin-turbo car only had 295 ft lb. Again the engine was probably restricted to avoid transmission problems.
As for LS series engines, they are usually run with very robust transmissions indeed in GM applications. Corvette has a rear transaxle installation but it's probably too long for a mid-engine car. Additionally, in that application it is fitted with an oil cooler.
Like many modifications I'm sure that yours will work out fine so long as you keep a heavy right foot off the throttle pedal, especially in low gears.
In summary, high torque engines are enthusiastic in their appetite for eating under-specced transmissions. It's no accident that the big AMG cars are all automatics, where the computer can implement clever torque management to protect the transmission from an ape at the wheel! Same applies, of course, in Porsche PDK applications....
You could try to find out what Lotus were using in the back of their V8 Esprit but even that twin-turbo car only had 295 ft lb. Again the engine was probably restricted to avoid transmission problems.
anonymous said:
[redacted]
That's interesting to know. Nonetheless, gearbox internals can be built to assorted specifications - and, of course, prices. I'd be surprised if Porsche have generously over-engineered the gearbox of Boxster just in case owners decide to double the torque of their engine. Hence my comment about the turbo 911 perhaps being more comparable.One thing about torque in a driveline is unquestionable. Big torque capability will only do damage if you use it. So it's fine to park outside the pub and get enthusiasts "oohing" and "aahing" over a flashy installation, and quite another thing to go jumping on the throttle in second gear.
Recall Porsche's poverty in the days when the S was first designed. The 996/986 saved them but the S design had to happen when they were still struggling so off the shelf parts use was the norm, not custom designs for uncertain and limited quantities of items that could be obtained as already designed items. I doubt Porsche did much more than minimal adaptation for using the 6-speed.
Some of the racers have built high horsepower engines but how much torque they produce I'm not sure. Jake Raby in the US at Flat6 produces 400HP flat-6 engines for the Boxster, might ask him.
Some of the racers have built high horsepower engines but how much torque they produce I'm not sure. Jake Raby in the US at Flat6 produces 400HP flat-6 engines for the Boxster, might ask him.
I still haven't decided... often boxes are actually a lot stronger than people think... my current mid engine car has over 700bhp and 600ftlb and I am still using the ford mondeo box (designed for 230ftlb) no real mods other than a quaife LSD and multi plate clutch, I abuse the car on road and track for many years and I've not broken it yet which is surprising.
Here is a vid link to show the kind of abuse it gets.
https://www.youtube.com/watch?v=d-23Wdq4etU
What i was looking to find out is if its a known weak box or if people had run it on high torque applications... of cause my car will be lighter than the booster which helps a box take more power than spec'd for.
Here is a vid link to show the kind of abuse it gets.
https://www.youtube.com/watch?v=d-23Wdq4etU
What i was looking to find out is if its a known weak box or if people had run it on high torque applications... of cause my car will be lighter than the booster which helps a box take more power than spec'd for.
Edited by andygtt on Friday 19th December 09:22
Second gear selection can be a weak point, but the specialists who rebuild them (properly) make small modifications and rectify this. Hartech do it and Mike at Sports & Classic specialises in them (I've seen lots of boxes arrive on pallets from many renowned Porsche specialists). Check with him but I think if you have a serviceable box without any issues then there's probably no need to do anything. On, pinion bearings can get noisy too, but it's not a widespread problem/weakspot.
Someone in the UK has a Boxster with a 996 turbo engine fitted that's used on track days - he'd be a good person to ask about this as that engine's 420b standard.
Someone in the UK has a Boxster with a 996 turbo engine fitted that's used on track days - he'd be a good person to ask about this as that engine's 420b standard.
worth mentioning, the reason a boxster box would actually be desirable as its designed for mid engine (i.e. box behind the engine).... the 911 box is designed to fit in front of the engine so in order to run it mid engine I would have to run it upside down (otherwise i would have 6 reverse gears lol).
andygtt said:
Dear god that's got some grunt in it - 155+ down Hanger Straight. Gassing Station | Boxster/Cayman | Top of Page | What's New | My Stuff