Tbred911

for sure it would... I try to change my tranny fluid every 12 track hours to mitigate premature wear

SH || NC

So the 4.0 is used already by the factory. Any additional maint required for the accelerated wear? Anyone know?

I think most of us here already change our tranny fluid at least once a year already.

Tbred911

it's not a 4.0 they use in the RS... I believe it's a 3.89

Rob S

I agree that the best reason for changing to a 4.0 is for tracks where you need 2nd gear in certain turns, and 2nd gear is too tall in a stock box. That describes every track I know of around here. In fact, one nearby track had me in 2nd gear six times per lap. And there's nothing more frustrating than bogging in 2nd because the engine has dropped out of its usable torque range. Had it not been for my desire to have a lower 2nd gear, I would have been happy to stay with stock gears.

On my previous track car, a 500+ hp 930 with a 4 speed, I changed 1st gear to be much taller (equivalent to a Carrera 2nd gear) in order to make 1st a "track gear." I would regularly shift into 1st for the slower turns. It revved out at 72 mph in first gear, which was perfect for coming out of the hole on the slower turns, but it was hell for starting from a stop. In that car, I ran with a stock 2nd and greatly reduced 3rd and 4th gears, so all gears were active on the track.

But I'm surprised to hear that someone reported slower lap times in a GT3 on a track just from changing to a 4.0. The GT3 has such a broad torque and rev range, with so much overlap gear to gear (whether stock or not), and six ratios, that these all conspire to create an enormous "sweet spot" for track usage. I'm not suggesting that the 4.0 is the necessarily the best way to go for everyone, but I can't imagine that the overall lower ratios of the 4.0 would make it "slower" anywhere, unless it's limited by the reduced top speed in 6th gear (or possibly some fluky, uncomfortable gear changes unique to a specific section of a certain track, which could happen no matter what gears you have). There's no disadvantage to running up a gear if that's what the track demands, and that's where the the drivetrain is producing its maximum benefit. Even if you have one track in your stable where the 4.0 doesn't buy you much, it's likely to buy you quite a bit at other tracks you might visit.

As several have said, everything is a compromise...

SH || NC

Slower maybe because of the increased volume of shifting required?

At least for me, I know I am faster through certain sectors if i stay in a particular gear and ride out the torque, instead grabbing 2nd perhaps in a couple slower sections.

996FLT6

The tracks here in NorCal I use 2nd gear on tite turns on stock r/p. With 4.0 r/p I keep it at 3rd. Thill it's basically 3/4/5 . ls and sp is 3/4. If stock r/p it's 2/3/4 for all tracks mentioned. 3rd gear feels like a 2nd gear pull. Mike

Rob S

I agree that's the other tradeoff -- each shift takes time. But depending on exactly where the shift points occur for a stock vs. lowered-ratio gearbox on a particular track, the shorter ratios may or may not cause you to have to shift more frequently, but they will cause you to shift at different places on the track, which might not be as comfortable. But this problem occurs whether you've lowered overall gear ratios by changing the R&P, or you've done so by changing individual gears.

Back when I was racing a 911 with a 901 gearbox, we'd change the individual gears for every track, to optimize everything. I can't imagine doing that now!

88 Club Sport

Thanks for all of the feedback on wear etc. I generally get 10 days in per year and change fluid at the begining so I think I'll be good in regards to wear. As for whether the 4.0 is good for HPR, I just signed up for the DE that is conjunction with our Club Race in August so I will find out soon. Can't wait to experience the GT3!

Tbred911

Going from 2-3-4 to 3-4-5 with a 4.0 would increase your laptimes! ThIs is what to want to a avoid. A 3.77 would have served you better at that track as you still would have been in 2-3-4 but shorter gears and more accel! Having said that gearing is never perfect. U need to look at the tracks u drive on and analyze entry speeds taking into consideration gear range with your new r&p and see if your staying in same gear or going higher and where in the Powerband you are in the new gear setup on exit.

996FLT6

^there's only one section at thill that I go to 5th gear(straigtaway into t1). Rest is all 3-4. But I agree everything is a compromise with what tracks u run. Can definitely tell u I'm faster because of r/p at ls/sp but thill not much at all maybe no difference. Only one area I'm faster in thill is through the esses. If I had to do it again I would regear vs r/p for longevity or not do it all. Stock ratios aren't bad either. Mike

Tbred911

it either really works on some tracks or there is no difference than stock... short tracks with 2nd gear corners.. it's great! depends what your application is... on a 996 3.6 I would go 3.77 3.4 I would go 4.0 or 3.77 and GT3 I'd be tempted to go 3.73 or slightly less than 4.0 if you wanted to avoid having to move up to the next gear... it really depends on application and track here as so many have concluded.

GTgears

Missed the bump until now. I don't subscribe to threads...

Both a regear and the short ring and pinion have wear and tear trade offs. They do accelerate wear.

The short ring and pinion makes every single gear in the gearbox spin faster. More rotations, more wear. Trying to empirically capture that with a number is a bit of a challenge though.

Doing gearing has the same issue, since short gears, again, are spinning faster. However, they carry with them their own burden, in particular 3rd gear. Take a look at this picture:


See how much that idler gear overhangs the dog and just how little meat there is between the root of the gear tooth and the inner bearing surface of the gear? We only give our super short ratio 3rd gears a 25 hour servicelife as a result.

For a while, it was super popular to put short little 1.789 or 1.750 3rd gears into DE cars with stock mainshaft and stock ring and pinion. I have actively discouraged this practice because the popularity of track days has skyrocketed and people started blowing up those short 3rds because they never timed them and didn't rebuild their gearbox and throw away that 3rd gear annually in the way that they should.

Porsche has partially resolved the problem for me by making the .7 GT3 run a 1.64 3rd. That's a pretty good ratio. The .6 GT3 runs a 1.56 3rd. I now sell a lot of 1.65 and 1.632 3rd gears to .6 GT3 owners.

If you go back to page 3 and look at what PJ did on his .7 GT3 it will make sense. He did the short ring and pinion with a taller 1&2. We kept his 3rd gear really close to stock, but changed it to one of ours just for strength reason. But it solves the whole 2nd gear debate you guys have been having. But that doesn't come without an obvious cost, however the reason he, and the factory, do it this way is to keep a more reasonable 3rd gear in there that is strong and durable. .6 GT3 Cups got the same 1.56 3rd that were on the street cars, with a 2.00 2nd and the 4.00 ring and pinion.

pete95zhn

Now beating an old (but hopefully not dead) horse here, but what would be a proper gearing for a tracked 996 turbo? Specs below:
-redline 7200
-available fwTq 700 Nm+ 3250-5750
-Available fwHp 500 Hp+ 5250-7000
-CUP LSD

3rd is toast now, so I anyway need to open the box.

Options:
A. Longer 1 & 2 with 4.0 R&P
B. Shorter 2-5 and save the long 6th for Autobahn blasts
C. Shorter 2-5 and move the 5th to 6th.

pete95zhn

OK, maybe this new question is easier to answer...?

Is there a longer final drive available? Like 3.00:1 Anyone?

GTgears

Hello Pete,

I missed your first bump but see your 2nd...

No, there's isn't a longer final drive.

Now for a turbo, you want very different gearing than with an NA engine. An NA engine revs around 1000rpm higher and has a much peakier powerband. The turbo engine revs lower and has more arear under the curve. If you gear a turbo gearbox tight and short like an NA gearbox you end up shifting way too many times and any and all gains you make on acceleration through mechanical advantage are lost in the time it takes to shift. Just yesterday Betim of BBI and I were talking about this on Jeff Zwart's car. 2 years ago he had it geared like a GT3. Last year we changed it over to taller more spread out ratios and Jeff got into the sub 10 minute club with the car at Pike's Peak.

So, to that end, you need to start by looking at your 2nd. You do not want to make it shorter. Many guys even make it taller and go with the GT2 RS mainshaft with a 1.89 ratio. That's less expensive by far than using my parts.

You have a 1.41 3rd in there right now. We often just replace that with the same, but like to look at the tracks you run (with in car video if you have it) and see if we can gain any time by avoiding shifts in awkward places. And then we largely treat it the same way we would a GT3, reviewing your top speed at your fastest track and building in the ratios from there based on what we pick for 6th.

Regards,

Matt

PS. Since this thread was bumped I think it a good place to mention that I am out of the ring and pinion business. I have ended my relationship with Ricardo and won't be making a new batch of them in the future. For the foreseeable future anyone wanting a 4.00 ring and pinion should get one through PMNA, or the RS 3.89 option through the dealership has proven to be a good midline to the stock 3.44 and the Cup 4.00