anders44

any high HP turbo/supercharged boxsters around?

how strong are the transmissions? I can choose from 5/6 speed 986, and the 987's really.

trying to figure out if it's a viable alternative to a GT2/996TT transmission and flipping that.

it should see 500RWHP and 7-800nm , to further stress it, it will se 335-345 hoosier/bfg R1 etc to put the power down.

god thing about boxster transmission is that it mounts pretty much directly up to my 951 torquetube. I tested with the tranny from my boxster when I was changeing clutch in summer.

easyC

the boxster S tranny is very strong..I know of a few that are running in teh 400hp range... but as far as flipping a GT2 or TT tranny, I don't think it is as easy as it used to be done for the 914's...

anders44

flipping them is not the problem, you get "kits" for that.

gt40s and other kits do it, ultima etc.

ruf has a 485hp? cayman S I think it is, with a narrow powerband, but dont know if the 987 unit is any stronger than a 986.

if I got this right

986 5 speed = aisin
986 6 speed = getrag
987 = aisin

you rarely see any talk about transmission failure in 986 forums, you do in 996 though, and the 986 unit is pretty identical, but with the R&P flipped.

the GT2/turbo unit is a G50 derivate and much stronger, also has another bolt pattern if I got it right.

kinda an expensive hobby to do major mods to car, just to have a $2500 burnout with a 986 6 speed so need to make sure first.

it will see track duty 90%, drag 5% and road 5%

Macster

be severely overstressing tranny with that kind of output and implied useage.

Run a 5 speed or 6 speed stocker to start with but budget for possible replacement. If stock tranny does not last long enough then you'll have to figure out an alternative. Not sure a 99x tranny going to be much better.

Might have to research an aftermarket "race" transmission solution.

Along with tranny figure clutch and rest of drivetrain going to suffer too. And surprisingly, some body/engine/chassis/drivetrain hard attachment points may suffer cracking from the increased forces being transmitted to/through them.

Sincerely,

Macster.

racer

iirc, the 986 6speed and 996 6-speed are the same, no? (yes i know one is "reversed" from the other).

In either case, the clutch is a weak link. I know a fella with a 986 5-speed who put in a 996 motor and cooked the clutch soon thereafter.

anders44

clutch isnt really a worry, as I use a chevy LS one. its so much bigger its silly.

thing is though, I will have 100% more power and torque than a 996 engine, and more grip than a boxster.


to macster, trouble with aftermarket trannies is the 20-40k price tag.

I know a 996 GT2 tranny will take it, but they are 10-14k usd. and lots of work to mount.

Ryan C

First of all the boxster 5 speed tranny's are the same one's found in the VW passat and some audi's, so I don't know what kind of strength you get. The boxtser S tranny is just a mirror of a 996 tranny so there is no need for a flipped diff.

I did your test fit backwards and fitted a 944 tranny to a boxster engine and I agree that it'll bolt right up. But I'm not so sure the same can be said for the six speed. They are a way different tranny and weren't made to go into as many cars as the 5 speed. They don't have as many holes around the bell housing and I'm not sure that the right 4 bolts will line up right.

Macster

needs what it needs given your intended usage.

There is some margin in the tranny. Someone posted the 5-speed same as used in VW Passat. Do a little research and find the largest engine or the one with the most torque output VW mated to the 5-speed and figure the margin's 1.5 times maybe 2.0 times that output.

Say VW mated the 5-speed to an engine that puts out 250ftlbs of torque then figure the margin is 375ftlbs to 500ftlbs. Doesn't mean this tranny will accept that much torque under standing start launches time after time without at some point spilling its busted guts all over the road as it lets go, but it means that it will take some abuse before it does this. Might be first launch, or the 1000th...

If you avoid drag start launches and power shifts tranny might actually deliver good service over a long time.

I'd certainly look into frequent tranny/diff fluid changes and maybe use some high performance tranny/diff fluid though I have no recommendations. (I run Royal Purple stuff in my GTO's 6-speed. But in my Boxster I run the factory fluid. Based on my experience and use of the car/tranny it is pretty good stuff.)

Sincerely,

Macster.

Macster

I don't recall the specifics but several times I've come across artihtcles on cars that come with an automatic and the comment is no manual is supplied because the automaker doesn't have one in its repertoire and a few times the capacity of the manual is mentioned and its not very much below the more powerful engine's output. My point is a transmission suitable for say a 200ftlb output engine doesn't have the margin to deal with an engine putting out twice that amount. It might suffice for an engine that put out say 250ftlbs.

Sincerely,

Macster.

sbelles

My 99 986 with a 996 engine puts out about 310hp. I'm on my 2nd 5speed transmission but the first lasted over 80k miles 30k of which were with the 996 engine and about 60% of those were track miles. The 2nd (used) one now has about 10k track miles. YMMV

Macster

are latest CAR mag has review of super hot Merc CL66. Engine produces approx. 760ftlbs of torque and is mated to 5-speed auto. However, engine's output is limited to save transmission.

A 7 or 8 speed auto is used in other less powerful models but doesn't have capacity to deal with this engine's torque output. A new transmssion that will handle the engine's torque output (sans electronics limiting of this which is now employed) is spec'd for the over 800ftlbs the engine can produce when unleashed.

Sincerely,

Macster.