Six Speed Swap Questions

[WizardSmokey]

Okay guys, I'm tired of blowing up 5 speed transmissions. Looking for some advice for going to a six speed. I'm running a Kennedy Engineering custom flywheel/clutch/adapter kit to a Maserati 4.2l V8. I'm looking to go from the stock Boxster G86.00/01, and am looking to go to a G86.20

My questions are simple: Does the six speed use the same clutch location as the five speed? Would I be able to just bolt the six speed where the five speed was? Are the axle couplings are the same distance from the bellhousing, so it won't ruin the axle alignment?

[Gilles]

Wow, what a beast..! For what I heard, the 5 speed gearbox is actually stronger than the 6 speed gearbox..

Perhaps your solution be an inverted G50 Porsche transmission that is designed to handle way more torque than the gearbox you are using, but those gearbox are pricey..

You may want to ask CMS as they have a lot of experience with these gearboxes https://californiamotorsports.net/

Good luck, and please share more pictures of your Boxster (..?)

[elgyqc]

That looks like the rear end of an old F1 car welded to the front half of a boxster... cool.
I can't answer all of your questions, but I can say the 6 speed bolts to an engine just like a 5 speed (I temporarily had a 2.7 engine in my Boxster S and there was no problem attaching the transmission). In your case I assume there is an adaptor plate in there. On the other hand the half shafts are further back then on the 5 speed, that's why Boxster Ss have a longer half-shaft that runs at a greater angle. The flywheel position is the same, but you need at least a clutch plate for the 6 speed because the splines on the transmission input shaft are different. If I remember correctly I ran the complete clutch (flywheel, clutch disk and pressure plate) from the S when I had the 2.7 installed, it bolted to the engine with out any problem.

[WizardSmokey]

I've never heard anyone claim the 5 speeds are stronger, lol. The 6 speeds are way more robust. They've just been more expensive than I want to pay, until now.

I have a whole build thread for the car! it's just hidden over in the Racing section.

http://986forum.com/forums/boxster-racing-forum/73840-joining-porsche-family-track-rat-style.html

[WizardSmokey]

Thanks, elgyqc, that's what i was afraid of. We situated the engine and trans so the axles are almost exactly straight with the hubs. I'd hate to ruin that.

[gonz]

IIRC itsnotanova said the 6 speed Cayman transmission was the stoutest of them but I'm not sure if he was ever able to confirm it.
Your car looks cooler every time I see it!

[78F350]

To supplement what elgyqc said, I put a 6-speed and 5-speed side by side to compare. A rough one-handed measurement while holding my cellphone in the other hand shows:
The 5-speed measures just over 7 inches from the face of the bell housing to axle center.


The 6-speed measures just over 8 inches from the face of the bell housing to axle center.

(note: the angle of the photo distorts the point I was measuring from)



If you are interested in a Cayman 6-speed transmission Woody held onto one for quite a while and may have it available cheap. His phone number has not changed, shown in the first post of this thread: https://986forum.com/forums/boxsters-cayman-cars-sale-wanted/81718-2000-s-3-4-%2416-000-a.html

[WizardSmokey]

Thanks for the help! I'll definitely keep that in mind. What's the designation for the Cayman 6 speed?

[nuvolari]

Beautiful car and would love to hear that if you have any online videos! As a huge fan of Italian engines, a Maserati/Ferrari V8 is just what the car needs! But before you commit to a 6 speed, check out what I've learned about these transmissions.

I have a 00 986S with a bad 6 speed and after lots of research, I've found that the 6 speeds have problems with two things:

1) 2nd Gear - Many Getrag 6 speeds suffer from 2nd gear problems which are twofold and obviously related. First, they will pop out of gear due to a flawed detent. There are aftermarket detents with different designs as well as one company that makes a different internal detent fork to solve this problem but the online info about their effectiveness isn't exactly clear. Of course, the detent problem tends to cause grinding of 2nd gear and damage to synchros and cones which eventually ruins them and will need replacement at about $900 for the cluster. Again, there are aftermarket products of strengthened materials but not much detail on whether they solve the problem or not. All this can be replaced by someone with patience and money; you can do it yourself with lots of the former and a fair amount of the latter. Youtube videos exist of a couple people who have done this and it looks doable although I have not done it myself.

2) Pinion Bearing failure - The 6 speed uses sealed bearings just like everyone's favorite Boxster engine feature and they aren't much good in the tranny either. And in order to replace the pinion bearing, the entire gear cluster on the output shaft must be removed. This is a lot of work but the main problem arises when removing the bearing. Apparently the shaft is hollow on the 6 speed and as a result, it requires an internal tool for support when using a press to remove and install the bearing. One person online has used an old shock hardened steel shaft to good results for this tool and another has posted online the exact specs needed in order to make this tool. But another problem is that a standard hydraulic press is not strong enough and a special press must be used which apparently is very difficult to find. The actual specs for the press are online somewhere but I can't remember them exactly. Then you have to find someone willing to do this and who knows how to do it.
Oh, and if that doesn't scare you off, Porsche specifies that the hollow shaft can only be reused twice and after that, you must replace the shaft which if you have to ask the price, you can't afford it! So, how long should a pinion bearing last? Some people do get many miles but one Porsche transmission expert told me the pinion bearings are only good for 60,000 miles. I suspect that's worst case scenario but for the kind of power you're using, it's a serious concern.

Then there's the cost to buy a used 6 speed, which generally runs from $2000-3500 and definitely more towards the high side. And you never know the quality and condition of the internals, compared to around $500-1500 for a 5 speed.

The pinion bearing can be checked for failure by draining the oil and reaching into the transmission with one finger towards the internal magnet to check for the grey grease and metal shavings from the bearing.

Here's some YouTube about all of this:

https://youtu.be/i6m4b7D5HEE?si=CRt-zN4dNFD1huUO

https://youtu.be/1cdbNDdnp_M?si=hMMYjHl0QkcB9kxG


https://youtu.be/AveToZsaBeM?si=rWrhdSuhE0bZgfDu

And here's one of the better step by step instructionals I've ever found with much info:

https://rennlist.com/forums/attachments/996-forum/1100690d1477169951-996-transmission-rebuild-and-pinion-bearing-replacement-diy-996-g.96-transmission-rebuild-guide.pdf