5 / 6 Speed gearbox differences

[Giff]

My '06 2.7 5 speed needs a clutch.

Rather than simply replace it and seeing that I will have the gearbox off anyway what parts would i need to convert to the 6 speed?

I see the clutch is different so I think I would also need the 6 speed flywheel, are the cables and gear selector the same?

There also seems to be G87.1 and G87.2 6 speed gearboxes, how are they different?

Cheers.

 

[Buddy]

Giff, I'm not sure if this will be of help as it doesn't seem to differentiate the 2.7 well at all and the 3.4 Gearbox may well be different on the final drive or maybe the input. 6 speed was a rare option taken on the 2.7 the link below takes you to the Porsche website where you can select the PET from 2008 for the 987c I also have the PET for 2006 it may be a little large for emailing but if you email me your address I'll try to send it. For whatever help it may be as usual it can be a case of searching lots of sources to put the info together. http://www.porsche.com/uk/accessoriesandservice/porscheservice/originalparts/originalpartscatalogue/

 

[Buddy]

A bit more info I gleaned off one of the multitude of websites. A 5-speed manual transaxle is standard on the normal Cayman (G87.01), while a 6-speed manual (Getrag 466) is the default for the S (G87.21) and an option on the normal (A87.20). An electronically controlled 5-speed automatic transaxle (Tiptronic) was also available on the S (A87.21) and the non-S version (A87.02) So it would seem that you need the A87.20 unit. As ever hoping this helps[]

 

[Motorhead]

Giff, clearly you're the sort of chap who enjoys a challenge but I don't think that you'll be able to convert your 5-speed 'box to 6-speeds. The 3.2-litre engine used in the 987.1 required a gearbox with a higher torque capacity than that used in earlier models and a new 6-speed gearbox was produced by Getrag to Porsche's specifications (this 'box was different from the earlier 6-speeder in both construction and ratios). This 'box is entirely different from the 987.1 5-speed gearbox which was a development of the earlier unit. Note that the Cayman and Boxster have different gear ratios too. Even if you were able somehow to convert your 'box to 6-speeds, the cost probably would be prohibitive because you'd be changing shafts, gearsets, selectors, bearings, flywheel, diff, etc. and the car could turn out to be a pig to drive because the ratios are ill-matched for the 2.7-litre engine's torque. If you're determined to go ahead, I would have thought that it would be better to source a second-hand 6-speed gearbox and flywheel. That way you could could check compatibility and driveability and, if necessary, revert back to the 5-speed unit. Good luck with your quest. Jeff

 

[Giff]

Thanks for the replies, I will pm my email address as I would appreciate the '06 PET. To summise, the Boxster/Cayman Getrag box does seem to have been used on the 2.7 as the option so I'm making an assumption that a 3.4 box will bolt on directly to the 2.7 block. What I need to find out is if the different make gearbox also uses different engine moutings and if the driveshafts are also different, so the '06 PET shoud be invaluable! I do plan to source a low mileage second hand boxster or cayman getrag.

 

[Buddy]

PM is notoriously poor for contacting people but I've generally found that emailng through the profile pages does work at least most of the time[] As Jeff says, to convert a 5 speed box isn't practical but to swap a 6 speed into the 2.7 should be good. Anyway it's a case of identifying a secondhand box.

 

[Giff]

Email sent. Only other problem I can think of are speed sensors, I wish you could get a decent workshop manual for these cars!

 

[Motorhead]

Giff, here are some ratios for the G87/200 6-speed gearbox introduced in 2005 for the 3.2-litre Boxster (3.4-litre Cayman variant in brackets): 1st 3.667:1 (3.308:1) 2nd 2.050:1 (1.950:1) 3rd 1.407:1 4th 1.133:1 5th 0.972:1 6th 0.882:1 Reverse 3.33:1 (3.00:1) Final drive: 3.875:1 Some comparative figures for the G86/01 5-speed gearbox fitted to the MY2000 2.7-litre Boxster and the 6-speed gearbox (developed from the 5-speed) for the same year : 1st 3.500:1 2nd 2.118:1 3rd 1.429:1 4th 1.091:1 5th 0.838:1 Reverse 3.440:1 Final drive 3.560:1 1st 3.820:1 2nd 2.200:1 3rd 1.520:1 4th 1.220:1 5th 1.020:1 6th 0.840:1 Reverse 3.550:1 Final drive 3.440:1 I wouldn't have thought that an adapter plate would be required to fit the 6-speed 'box to your 2.7-litre motor but it's important to confirm that your transmission mounts and driveshafts are compatible. Jeff

 

[Giff]

Looks like the Boxster 6 speed would suit the 2.7 better than the Cayman variant.

 

[Motorhead]

Lower internal ratios and a lower final drive ratio would work in your favour Giff. Unfortunately, there aren't any workshop manuals available for the Cayman, but you might like to take a look at Porsche Boxster, Boxster S Service Manual 1997-2004 published by Bentley (£66.45 from Amazon). Jeff

 

[uknick]

Giff The 2.7 with a 5 speed box has a lower VED than a 2.7 with a 6 speed. Something to do with how they run the test for emissions. I assume if you make the change you will have to notify DVLA.

 

[Buddy]

On the other hand Nick I doubt they would willingly accept me paying less road tax if I took out the 3.4 and fitted either a DFI 3.4 or a 2.7 Engine![]

 

[Motorhead]

ORIGINAL: Giff Only other problem I can think of are speed sensors.....

Another thing you're going to have to address Giff is that the change in gearing is very likely to throw up ABS/TC/PSM faults because the front/rear wheel speeds are outside the limits expected by your DME. The instrument cluster also uses the average of the 4 wheel speed sensor signals for the speedometer. Jeff

 

[Giff]

Knowing the old Bosch unit fitted at that time (to almost everything) that shouldnt be a problem, it certainly works on the ABS sensors. Very unusual to have the speedo running off them though, are you sure?

 

[Motorhead]

ORIGINAL: Giff Very unusual to have the speedo running off them though, are you sure?

Appararently so Griff, according to a recent post: http://www.porscheclubgbforum.com/tm.asp?m=750037&mpage=1&key= The signal's also used to trigger the rear spoiler deployment. Jeff

 

[Buddy]

Jeff, I don't think that a change of ratio should effect how the PSM or ABS throws up warnings as both work on a comparative basis of the wheels rotations. Changing the size of one pair of wheels would effect this as they would then roll at differing rates but it will effect the engine speed relative to the road speed and unless there is some comparative reference there it should cause no problem. Last week I helped my son change a wheel bearing on his VX220 turbo, there had been a noise from the wheel checked by the garage and passed ok! But then the ABS light came on and his speedo was erratic. The bearing had the sensor built into it and a wire had broken, so, we changed the bearing and all was ok again, the bearing was quiet too. A similar thing, one sensor down things acting up! It's some time since we had cable driven speedometers but we do tend to think of these things as from one point, it's actually a benefit that they can sense the speed off any or all wheels.

 

[Motorhead]

Hopefully that will be the case Kevan. I was just thinking that for a given transmission/final drive the DME might be programmed to expect the front and rear wheel speeds to be within predefined limits for normal driving but maybe it's just looking for anomalous signals before intervening. Modern electronics - too damned clever for their own good sometimes but great to have such sophistication on-board most of the time..! Jeff

 

[Buddy]

Jeff, agreed on the modern electronics! Great unless they go wrong!!!! But, mercifully they do seem to have a good average of reliability unless they get wet which is more likely in the CC or Cayman Convertible.[] I don't see any reason for them to program in a differential comparison through the transmission unless looking to indicate for a broken driveline but that is usually quite apparent to the even the dimmest driver! I'm looking forward to how Giff gets on with his project as I'm sure others would like to do likewise.

 

[Motorhead]

Absolutley Kevan. We all wish Giff the best of luck with his project and look forward with interest to hearing about progress (and seeing some pics too?). Good to know that there's someone out there having a go at modifying his car - too many "couch mechanics" (sadly, myself included..!) on these forums. Jeff