5 vs 6 speed pros/cons
 

I know the 5 speed has a lower final drive ratio.
And I know the 5 speed is much lower cost initially

This is for my 914 project so very light car. Will have around 250 - 300 HP.

6 speeds are known to have 2nd gear pop-out / synchro issues, also well known in the 996 series which uses the same transmission albeit inverted. Go with the 5 speed.

six speeds have reverse in the wrong place on the shifter! all the years of muscle memory have confirmed that fact to me. allegedly the six speed is a more durable gearbox, but I have not had any problems with my 5 speed so that is an unconfirmed rumor as far as I am concerned.

6 Speed has one more speed than a 5, so more is always better.....right?

The 6 speed driveshafts are at a rather steep angle compared to the 5 speed. So the boots wear .The 6 speed is a very expensive/difficult gearbox to repair.Just do a search and you will find mention of very expensive tools and massive force required.Not a great diy proposition.
In your case the gearing of the 6 speed is unhelpful unless you plan to remove tree stumps with 1st gear :-)?Your car will be so light/powerful,the 1st gear would be somewhat useless except for generating tire smoke.

300 hp may be too much for the lil 5spd which was only rated for 250 or so. It may survive with a good trans cooler. I do think the ratios are better for track work though.

as a previous owner of a 01 boxster S with 75K miles 6 speed.
and a current owner of a 99 boxster base with 160K miles 5 speed
i'm telling you, go with the 5 speed. its a night and day difference.

Hey there Guys,

I have quite a bit of experience with both of these gearboxes, so I can answer some of the questions that have come up here.

The 5 speed would certainly work well for you. It is geared pretty low, but then so is the 6 speed. It is however far less durable than the 6 speed.

It really depends on which of the 6 speeds you decide to use though. There are two of them to chose from. The 986.20 and the 987.20 one is out the Boxster S and the other is out of the Cayman S.

If it was my build, I would try to find a good low mile G86.20, do the detent mod on it and rebuild it prior to installation. It is a very strong gearbox, and with the detent mod done along with the rebuild, it will be very durable. You will want to make sure to take care of the 1st and 2nd gear as much as possible, but 3rd -6th are pretty strong, and can be beat on without fear of breaking them. I would also recommend a good differential. My personal favorite is the OS Giken, but there are several out there to choose from.

Feel free to give me a call if you have more questions, I would be happy to discuss the pluses and minuses of your choices out there.

Erik Johnson
(970) 344-7761 phone

Erik,
Thanks for giving your expert advice. The gearbox gets very little attention on the Forums. As the cars age, the gearbox issues will become more of an issue for Forum members. So your comments are useful and most welcome.
The cost of repair/rebuild for the 6 speed will also become more of an issue as the value of the cars declines but the cost of parts and labor increases.
So people will understandably try to do diy repairs . There have been very few diy gearbox repair threads here.
http://986forum.com/forums/performance-technical-chat/52817-transmission-repair.html
Second gear problems on the six-speed gearbox - 986 Series (Boxster, Boxster S) - RennTech.org Forums
This was the best link- a long pdf of a complete 2nd gear repair and even a photo of the Kukko puller they used. but sadly it is now dead:
http://itguynetworks.com/articles/boxster/2002BoxsterSTransmissionRebuildDecember2011Revisio n3.pdf

Run the 2.5 5sp. Want to upgrade later? Use the 987 BoxsterS 05-06 6sp. Shorter ratio's than the CaymanS 6 sp. I have multiple cars with 300-340hp through the stock 2.5 and 2.7 5sp transmissions. We can break them, but so can a 201hp 2.5. No need for coolers/etc. Cooling the trans does not stop the teeth from sheering off of 3rd gear :)

I have a 2004 986 S and want to investigate a lower final drive.

What are the ratios on the 2005/07 987S?

Brad - when you say use this box do you mean transplant the gear set or will the box just bolt up?

The 6 speed is "1" faster.

http://986forum.com/forums/uploads01...1444655611.jpg

What's the weight difference between the 5sp and the 6sp?

You have never driven an early 911.

You want to talk about a messed up shift pattern.

R 2 4
1 3 5

I think the 986 5-speed is about 50 lbs lighter than the 986 6 speed. the 987 unit is a bit in between the two. if I recall correctly from when I looked into it, the 986 and 987 6-speeds share the same slave cyls and hubs so are a relatively easy swap. the 986 5-speed is different. all have unique axles and shifter cable arrangements. you can use 5-speed axles with 6-speed hubs but will have less axle thread to nut on to. other than that, there are variations in the 986 5-speed gearing and flange dimensions over the years, and even more variation if you start looking at the interchangeable audi 012 units. the 987 boxster and cayman 6-speed also differ in gearing. also, I think that, in the case of these transmissions, mass is proportional to strength - the 986 6-speed is quite strong, the 987 unit less so, and the 5-speed is easiest to break. however, being lighter/smaller (shorter) they have better axle geometry than the 986 6-speed.

My 1998 3.6 has the original 2.5 5 speed, no issues, over 100K on the gearbox...

What's the detent mod and what's the reason for doing it? I'm planning on running 400+bhp on a G86.20

Here's what I have read. The modified detent allows the 2nd gear selector to engage a bit more deeply, reducing synchro damage and gear pop out.
I fit one to the transmission because of a minor crunch on the initial 1-2 up shift of the day before the gear lube warmed up. That was 2 years ago, and it hasn't recurred since.

I installed the detention a few months back to address the same issue and it has not happened since.

The 6sp trans has a 2nd gear pop-out issue. I had to rebuild mine at 142k. I did the G-box detent, I'm at 180k no issues.