"02996ttx50

i dueled one of those on mulholland's "snake", and we couldn't get away from each other and live to tell. he was older than me kinda dude ( if such a person exists ) i think his walnuts shriveled a bit after a few....we traded spots a few times as well. no slouch, that car...and mine 13 years older and maybe a cpl 1/10's faster? i'd like to think so LOL

ScottKelly911

First thing, see if there's anyone in the area also with a 996TT and maybe ask to switch cars for a short drive. Good place to find said person, either here on RL and set up Sunday morning canyon drive or you can go to a Cars and Coffee where there most likely will be another 996TT. This will have you see how another one handles and you can also get the other person's opinions on how your car handles, whether it's the same or feels different. That is the first and most cost effective. Then, if it still feels "weird", time to start diagnosing. You've gotten some pretty good advice already, alignment, are the tires old? etc. But another thing that may be an issue is if the LSD has gone out. I know it's a common problem in the 3's and 2's, so wouldn't surprise me if it's also a problem on the Turbos. A lot of times, people don't even realize that it's gone out, it just "feels weird".

Good advice on the track, for the streets getting onto a freeway or turning onto a 2 or 3 lane urban street, not so much. I can just see someone doing that while turning from La Cienega onto Sunset, then promply putting their car into a light pole lol

Olemiss540

Come on. I think Carlos was trying to illustrate why the 996tt would "feel" different to a new owner. Maybe it would be different if he suggested trailbraking deep into the intersection!

"02996ttx50

that is a bit confusing? the lsd went out in his stock car? umm...

but hah! that corner at la cienega and sunset is a real clutch burner!! i would avoid that top of the hill red light at any and all costs! i know that corner all too well!

996tnz

^^^^This! And coming out of the corner, mentally aim a yard or so inside the track out point and let the gas pedal carry you out to the edge.

Coming back to Walleye's impressions, when driven at the limit the viscous front diff does make for some unusual handling. Depending on how well you've ensured your rear tires rolling diameters are a bit smaller than the fronts (think about 2% or so is optimal but it's a while since I looked at it), you will have greater or lesser lag in torque transferring forwards when the rears spin up. Up to 40% eventually goes to the front according to Porsche. I've never been able to track down performance graphs for that front diff, but having done about 35,000 miles in mine, including some circuit race miles each year, I don't believe the 996T can sustain sending much torque forwards for too many seconds before overheating and reverting back to essentially rear while drive again. My front diff is working but there is no way the gas pedal pulls you straight at the end of a sustained drift in the way that say an Audi quattro system does. But despite that inconsistently variable torque split (probably behind your front-rear axle disconnect impression) I still prefer the 996T system for road and track as it ensures the standard dynamics of the car are pretty much 2WD most of the time.

Found some more info on that after wrote the above so have added it to this post. If following the link, just note that the Golf has the wheel diameters staggered the other way but that's because it is primarily FWD versus RWD for our Turbos:

"The disadvantage of a viscous coupling is that it engages too slowly and allows for excessive wheelspin before transferring torque to another wheels. This is especially critical in automatic all wheel drive systems - when cornering under acceleration, the rear end is engaged with a slight delay, causing sudden change in the car's behaviour fron understeer to oversteer." http://www.awdwiki.com/en/viscous+co...r_differential

The PSM can also make for some weird handling. Once past 7 or 8 tenths on track, it will serve up increasingly odd (read awful feeling) gas cut and understeer behaviors while trailbraking unless fully disabled by unplugging the connector under the brake fluid reservoir. Doing that does also take out the e-LSD and e-biasing of the brakes but is still the lesser of the evils in my book.

Along with the Turbo's AWD understeer under power on exit, that lack of a proper LSD means that seeking to carve corners doesn't deliver as much speed out of the Turbo as it might in say a GT3 as the inside wheel starts spinning up before the limit. So yes, in slow and medium corners I aim to rotate the car with trail braking to allow earlier gas and a straighter exit as Carlo_Carrera suggests. And/or look to jump the kerbs more deeply to straighten the whole line, though this works best on track tires as they generate enough G to unload the inside to the point where doing it doesn't unsettle the car more than its worth.

If your car is feeling seriously weird, you may well find that your rear tires have a bigger effective rolling diameter than the fronts instead of the other way around - whether through specs, wear or inflation pressures. I don't know if that front diff is symmetrical and throws torque the other way too, but if it does then any over diameter rears are effectively trying to brake the fronts under normal running with, say, 5% negative torque. Then when those oversized rears start to spin up the front would go through a neutral patch until positive torque finally flips forwards. Again, I've never been able to find response curves for the front diff but having driven her the odd time with slightly oversized rears (eg 265-40-18s IIRC on 10 inch rims or else new rears with worn fronts, but not more than a few percent oversize so as not to damage the coupling), it's a pretty certain way of getting a Turbo to feel as weird as you describe.

And yes, the Turbo feels far more lively and responsive with zero front toe or even a smidge of toe out.

MotoJB

Powdrhound, 02996TTX50 & 911mhawk;

I have the engine mounts switched to 964rs sports. Should be good there now.

As far as the trans mount, my shop came back saying this:
"After we spoke about the transmission mount, the Torque solutions inserts were already purchased and installed. If you would prefer the OEM 997 mount, I can definitely replace this for you, however the labor to install the inserts will still apply."

Pretty weak but whatever. Question for you guys: should I really skip the torque solutions t mount?

Will I get a big increase in noise/vibration by going to the TS 75a street mount? I also have a UMW LWFW and clutch setup...I'm also concerned about what I read to be a big increase in noise coming from the flywheel with the TS mount.

Should I spend the extra dough to have the stock 997 trans mount put back in? My shop implores me that the TS is a better performer and that the difference in NVH shouldn't be bad at all.

Thoughts? Thanks for your continued help/input here.

"02996ttx50

if i had my druthers, i'd simply go for the oem 997 mount. but i wouldn't pay a dime more to have them swapped at this stage since they've already inserted the inserts etc.. just go with what they installed the ts inserts etc. you'll be fine, *if* they are the "street" version. that's *supposed* to be a mid level compromise in nvh.

no reason to pay to have them swap that i can think of. i predict you'l be fine as they are.

MotoJB

Thanks...and yes, the street version. Thanks also to Pwdrhound for the email/input.

Anyhow, they said they'll swap it out (during future work I plan on doing there) if I don't like it.

911mhawk

JB- Good call on the clutch kit/FW, you'll appreciate it in conjunction with the new trans for downshifts and general quick rev feel. On the trans mount, see how it feels, my guess is it will feel great compared to the worn out one!
THe NVH concerns are overboard here, you seem performance oriented and will be fine.

MotoJB

The UMW clutch/FW was already on the car...shop says the clutch still looks good. Thank goodness.

Thanks, I'm hoping that's the case.

911mhawk

I can appreciate your situation, the steep learning curve via a new trans is good for knowledge but kills the wallet. At least you know you have a keeper now!

"02996ttx50

motojb..

your setup should be great for a dual purpose driver. to 911mhwk's point about being "overly" concerned about "nvh" as you know it's cumulative.

try driving around the city in a lowered 996 turbo with oh let's say solid motor mounts, modded trans mounts, cup cables/shifter, and just for good measure throw in some solid sub frame bushings, and lastly straight cut gears for good measure to test the mettle of your ability to handle "nvh" as well as the integrity of your dental work. lol.. but i kid.

just don't think nearly every performance mod particularly those involving where the rubber meets the driveline, do not affect nvh cumulatively, and everyone's threshold for enjoyment VS performance is different.

sometimes it's one thing that can take your car over the edge from being a DD to a track car. though one thing alone isn't gonna do it? many will .. but you are on the right track and what you've added will be great.

MotoJB

Thanks...one things for sure, you spend that much dough, you pay attention and start learning.

Yeah, its a keeper. My wife won't let me buy anything else after this one.

Thanks man.

Noted...and I will stay with OEM motor mounts and skip those other track oriented mods to ensure it stays a bit more street worthy.

I sense my threshold is a bit higher than many/most, so It'll likely be livable.

Thanks for the continued input/feedback. Learning from you guys is appreciated.

"02996ttx50

we all learn from those that came before us.. then there are guys like pwdr that have tried just about every combo of any/everything..

just to clarify.. i was suggesting that you stay with the ts inserts because they won't add unlivable amount of the ( again ) nvh and for a guy like you, as you say.. you'll be fine. i think if i read him correctly ( and he has been kind enough to advise me in the past ) the 997 TRANS mount is more than sufficient for most all day-to-day needs.

if/when you DO? get back in or question the integrity of your motor-mounts? ( if they haven't been replaced yet since "new"? ) then i would suggest you go with some reputable SEMI-solids ( rss/wevo etc ) as they are more than worth the initial added nvh ( noticeable yet easily livable for a dual duty car ) and have a much more pronounced and connected driveline feel and in concert with a new t-mount, it will be night vs day over the old oem and presumably "worn" parts.

i just wanted to clarify that it was the "inserts" on the t-mount that i wouldn't wan't to pay extra to swap out given you'
ve "paid" and they're already in. you can "handle" the semi's on your mm's also, without it getting "harsh". again, just remember "cumulative" and enjoy the elimination of ALL lateral slop. i trust you have an ssk or a numeric or something planned if the car isn't already equipped with one? if not that's the last in that sequence of parts i feel needs to be addressed from stock. again dual duty. not grocery getter.

either way, you're well on your way! and cheers.

MotoJB

Thx for the continued thoughts/input.

Well they have both the 964rs and RSS semi-solid motor mounts in stock for me...I can choose to go with either at this point (in conjunction with the TS 75A t-mount). I simply have to make my decision!

Car supposedly has a 997 ssk on it right now...