Great thread Mike.
I just had my Sachs Stage 2 upgraded by Clutchmasters since it started to slip after Tony's EPL custom tune.

The new clutch is more on / off but drivable on the street . pedal grab is very high....but it holds the power.

At the same time i changed the trans fluid to Delvac and I notice that the LWFW clatter is much much quieter. That would lead me to think that it has much better lube and cooling qualities. Are you using Delvac for track work ?

Elliot

 

my $.02 worth here.....as I see a few critical points "unmade" as I also am wrestling with how far I need to go with the planning of my "preventative" rebuild to handle at least my crappy driving.

apologies in advance for the excessive use of emoticons. couldn't find bullet points.

note the differences between the tt box and the gt2 box and consider the relatively minor performance differences of the whole drivetrain.....if one were in the Porsche warranty department/design team meetings....one may have suggested that a cooler should be placed on a 'box that had an LSD and was theoretically aimed at a more hardcore driver's vehicle. (i.e. "hey boys we're near the ragged edge on what the tt box/gearlube will cope with as it sits @ 415fwhp!")...

in a similar meeting elsewhere in the building(s)....."yep, we could make the transmission as overbuilt as the 930 transaxles but we have the constraints of space/ease of shifting for an average-underskilled driver/fuel economy/strict EU noise regulations/price point/weight/ and eleventeen other items to consider- so we'll have to wait until we build a car that retails closer to $200k USD before we can even do some of this cool stuff"


this week, a Porsche reman box currently runs about $9000 with a $1700ish core charge...50+/- on the shelf in Germany didn't see one here stateside.

short shift kits even/especially on these wonderful cable shift transaxles will shorten the life of synchros & operating sleeves because anyone can easily shift faster than the synchros can do their job

the motorsports cooler and squirters can be installed in these gearboxes without much drama. Seemingly two good ways to do it...and the less expensive one is about as much as a pretty nice watch.

an aftermarket cooler elsewhere in a good airstream will cool very well....sometimes too well for those of us who drive our cars on cold days...unless you run a thermostatically controlled cooler.....or with a coolant interchange to help with warmup.....

Porsche engineering really shines in their racecars.....look at what they did on the 935/917/956's to help those boxes live with power levels not unlike what some/most? of us are running!!!! in cars that weigh effectively half of what ours do....with an expectation of longevity listed in double digit hours!

easily available US gearlube is mediocre at best...

despite all this...they are pretty friggin sweet gearboxes in a pretty friggin sweet car!

 

Mike it is a big deal, been there done that.

But I really want to be honest ( been through three trannies until my ultimate rebuild) I think the hardest thing on any tranny is the driver and his skill and style on heel toe shifting and rev matching. if this is done well I doubt any real tranny problems will creep up. in the heat of battle we all miss shifts or screw up rev matching or whatever, that is probably harder on the tranny than anything else

also lets be realistic the tranny and whole car is a consumable. **** wears out and faster at the track so upkeep and rebuilds are on the menu look at the Cup car care, why do they do that so they dont have failure.

weekend warriors tend to run their stuff into the ground and then complain about gee I cant believe my R+P gear gave out (did that also)

I am open for therapy

my baby.....(and on the other side since my super rebuild tranny has been flawless but yes before next season I will open it up and freshen things, that my friend is the way of the car and track)

 

Tom, That is exactly WHY we should have a cooler on this car... It's heavier than the GT2/GT3, and MUCH HARDER to heel/toe shift with the dual mass flywheel. I look at the trans cooler as a preventative measure to help prolong the need for a rebuild... Any rebuilds will be the only option, now that our gearbox is OUT OF PRODUCTION (according to both my indy and Kevin at UMW), which means you can't just order one from the dealer.

Also, I'd say with few exception, most guys here don't view their whole car as a consumable... You're in the minority because you've taken the steps to become a race car driver of a 911 turbo. It's a consumable to you. It's a treasure and joy that most of the rest of this group like to enjoy on the track once in a while... If they can stave off a $5K rebuild, it makes perfect sense to spend the money on the parts for the cooler to have a competent mechanic instal it.

If any of you guys are going a full trans rebuild, you should seriously consider upgrading to the setup Tom has... Yea Shyte wears out... Yea, people are abussive on the tranny box. But Porsche intended this car as an executive GT car and NOT a track car... Now it's being tracked in ever increasing numbers... To each, his own, but when my box finally gets a rebuild, it'll get a cooler and sprayers at the 5/6 nose cone...

Mike

 

duel mass flywheel get rid of that!!

and to the guys that track "once in a while" I wouldnt do anything other than change the fluid once in a while, the rest for them (not you Mike) would be overkill IMO.

 

so even tracking once in a while is ok without cooler? even if the heat builds up during the event, it isn't that big a deal?

 

Tom would definitely know with his experience, but I would think it depends on the track and your power level, from what I am seeing is a simple flash could be enough power to heat up the 5/6 gears, if it's a small track heavy on 1/2/3, probably would be ok, but with our UMW 2's and the driving we do, I think it's just a matter of time.

From lengthy conversation with out local indy, I'd say at least the GT2 spray bar and scheduled changes.

 

Tom, How many times was your gearbox worked on while you DE'ed the car?

If a guy is doing 4-6 DE days per year, I'd say just change the fluid after a weekend. However, If you're doing 10+ DEs per year and running in the advance groups running the top 5% of the participants, my comments stand, and by all means, if you're having that tranny dropped for ANYTHING, spend the cost of a reasonably nice watch (less than $3K) and get it done... It's CHEAP insurance...

DEers stand a much better chance of "missing gears" and botching heel/toes than racers with lots of experience. It just makes more sense to me that those "learning" would stand a better chance of stressing their boxes and although I agree that hamfisted shifters will cause more problems than anything else... I just think those who are dealing with high temps will increase the wear significantly...

Mike

 

I agree. and nothing protects from mistakes. ok I will change to if you are still DEing with street tires you are ok??

and yes over several years of DE without any mods I needed a few new syncros so I would call that "normal" wear and tear.

 

FWIW. In industrial gearing heat is a big factor in gear life. As oil heats up it will carbonize losing its lubricity and film thickness. Another factor is drive line shock. For the sake of gear life a 'little' give in the clutch dept. would help the gears. Fresh cool clean oil and nice smooth loads are gears best friends.

 

what temp is considered too hot for tranny fluid?

 

The question you need to answer is, what temps is the tranny oil seeing. I use to know the number where they started to break down, but for the moment I can't remember. I do know I exceeded the not to exceed number when I tracked my car without the oil cooler being on. I installed a tranny temp gauge and a manual pump. When I got close to the temperature I flipped a switch and the temperature came down into the acceptable range.











Bottom right LCD is the tranny temp. It displays the temp and blinks when oil temp reaches five degrees below set point.

 

How bad of an issue is this for spirted street driving and 2 DE's per year? Do we need to get a Trans cooler as well?

 

Tom. Don't forget this info was for industrial gears which are subject to lower stress and expected to last, but off the top of my head at 140F-150F no problem for 2000 hours, beyond 180F oil life degrades and would be best changed at much lower hrs. indicated by colour. Our rule of thumb was if you could touch the gear case for a full second you were probably ok.

 

No.

You're just as well served practicing your shifting as well, because even and ugrade and cooled tranny can still brake with improper shifting. Cooling is neccessary for longer and extended runs at high temps mostly on the track. Most times you will be focused on other things than shifting and going through the gears the fastest you will. That's when mistake occur. On the street, unless your shifting is really bad, you shouldn't see many problems, even long mountain runs which I've done before. The track also comes into affect by providing more traction especially with sticky tires, that tax the tranny and gearbox all the more.

The TT gearbox is tough and with the lag of an FI engine, the delay of the rpms on the blip make it little tougher to time. Much easier to blip in a GT3 IMO.