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Background:
Since I've purchased my car 6 years ago now the desire to change the gearing has come and gone some throughout the years. I've been on a quest to optimize this car for this track hobby I seem to be obsessed with. This past off season I finally decided to make a change because I had nothing else that "needed" to be done to the car other than basic fluid changes and plugs.
Ring and Pinion vs. Re-gear:
A hotly debated topic here for some time early on, based on my research it was of my solid opinion that for ultimate performance Re-gearing of at minimum 3-4-5 and placing 5th into 6th would have been the ideal solution. Actually, re-gearing 1-6 WITH a ring and pinion is the ultimate ultimate solution if budget is truly unlimited. Either way for ultimate performance do the re-gear.
HOWEVER... , also in my opinion from research, to get the proper short 3rd gear ratio into the transmission that 3rd gear then becomes a vastly accelerated wear item. I know one individual who has broken 3rd gear twice in the last 3 years in his car. Conversations with people smarter than I on this topic lead me to believe that 3rd gear would be around a 25-50 hour wear item if I were being preventative about things. I pulled the transmission myself in a 1 car garage with no lift...I can tell you that I'd rather stab my eyeballs out than attempt that every 50 hours of use.
To be fair, shorter Ring and pinion will also be a shorter wear item than the OEM ring and pinion, particularly the 4.00 : 1 unit (always hitting the same teeth on every rotation) That interval is not nearly as short as the short 3rd gear though.
So, I decided that ring and pinion was the route to go for me. Now to study gear charts and figure out which one was best. Mid Ohio is my home track and as such it got the most attention when looking at gear charts, but I also go to a couple of tracks with slightly higher speeds so I had to consider those as well. I really liked the 4.125 Guard option but was worried it would be too short for the Glen and VIR possibly requiring a shift to 6th gear that I didn't want to make. I then looked at the 3.89 and it would have been a great option too but was just a touch too tall if I'm going through all of this effort. So I went with the Porsche Motorsport 4.00 gear set. As I described before this is also probably the shortest lasting of any of the ring and pinion options but it was the right choice for me here given my personal criteria. It's also rather inexpensive comparatively at ~16XX euros through Carewal currently.
What you need to be prepared for:
If you are going to break into the transmission, you need to be fully prepared to do a compete freshening up of the largest offenders in the box. My car has 38k miles on it and there was nothing wrong with the operation of the box, no noises, no shifting issues, gear oil changed every 10-12 track hours yet upon opening up and inspection many of the critical bearings were starting to show wear that could not be ignored. My experience with Brian Copans was great, he's not far from me so he took the time to go over everything in details with me, but my spend was about 2x what I thought it was going to take for the install plus minor refresh.
Full refresh later my gearbox is better than ever, has steel syncros in all gears and is ready to rock.
Track Results:
Results for me come in time gained on the track and driving experience at the track. I still drive my car a good bit on the street (drove it today as a matter of fact) but that wasn't the primary concern.
My first outing at the track was in poor weather with really poor air (85 degrees and nearly 100% humidity) My best lap that weekend was off the pace of all of my previous bests. I left deflated the car wasn't quicker. I poured over data ignoring the weather conditions trying to understand how I'd made all of these changes and the car was slower!!!
2 weeks later I went back in near ideal conditions and within 2 sessions on good tires had not only posted a lap 1.1 seconds quicker than my personal best but I turned 4 laps in a row under my old personal best. I also made a couple of alignment tweaks to the car that based on the data allowed for a little more grip in a couple of places so everything said and with as much data analysis as I'm capable of (I'm no expert) I'd say the gearing was worth around .6 - .7 second per lap at Mid Ohio which is around a 95 second lap give or take.
There are 2 shift points on the lap now that were not previously there where I give back time so I'm excited to get to the Watkins Glen and other tracks soon to see how much of a gain I get at those facilities.
My Mid Ohio club lap...cause I'm pretty darn proud of this one...
Street Results:
Your results and or preferences might differ, but for me the gearing is just "Meh" on the streets. That said, I live in central ohio where there aren't any good driving roads so there's only soo much spirited driving you can do on the streets. If I had somewhere to go drive canyons or better roads I might feel differently, but for me I wouldn't do gearing mods for a street only car. Freeway cruising is the biggest thing to consider. If you're thinking about making gearing mods go drive your normal highway drive in 5th the whole time. If it doesn't bother you you'll be fine, if you don't like the RPM's for extended periods then you'll know. For me, these conditions were secondary but I though it important to point out here.
Conclusion:
I couldn't be happier. I'm glad I made the change for my situation. Hopefully this write-up helps those considering gearing modifications in some possible way. Feel free to ask questions on anything I may have missed.
The same tooth thing is an internet myth about the 4.0 CWP sets. It's all about the root count on the pinion gear. The ratio is how many times per rotation of pinion it takes to do the ring once. It's all about 8 teeth instead of 9 and that it just spins around more times.
If the matched ratios were a real issue not only would Porsche have done a 4.125 decades ago but they wouldn't use a 2.0 in 996 Cup. Porsche's 2.0 is 20:40. Our 2.0 is 16:32. I can't remember anyone ever calling me and saying the 16 tooth fixed gear broke. It is always the dog on the idler gear.
Congrats on the mod. You'll learn some new shift points on the tracks you run but once you settle in you will be faster.
When I bought my 996.1 it came with a cup diff and LSD. All i know is that it is a quick car and competitive with 997 cars (including 3.8s) at the tracks I run at which include short 60-67 sec/lap circuits through to Bathurst (150m elevation change and 2.25-2.35 sec laps).
When I bought my 996.1 it came with a cup diff and LSD. All i know is that it is a quick car and competitive with 997 cars (including 3.8s) at the tracks I run at which include short 60-67 sec/lap circuits through to Bathurst (150m elevation change and 2.25-2.35 sec laps).
I have Matt's (GTgears) guard internals in my diff. A testament to his product, the diff was built over 4 years ago and was still in exceptional shape and according to Copans needed no attention at this time.
There's always bigger and badder equipment out there at track days but in my experience a well driven 996 GT3 can still hold it's own against the best of them.
Once one has done the lsd clutches and 4.0cwp it is basically a 996 Cup gearbox. The only thing it is really missing is the replaceable 2nd gear.
Glad to hear the lsd is holding up. I'm glad it was Brian who did it. It has taken me years to get him on board. 3 generations of plates ago they were super aggressive and fast wearing. Brian refused to use them. He would buy brand new GT lsds and install Cup plates in my product. He's come to see that stuff is long gone and that what we produce now is the best in the business both outlasting and outperforming Porsche's own parts.
Once one has done the lsd clutches and 4.0cwp it is basically a 996 Cup gearbox. The only thing it is really missing is the replaceable 2nd gear.
Glad to hear the lsd is holding up. I'm glad it was Brian who did it. It has taken me years to get him on board. 3 generations of plates ago they were super aggressive and fast wearing. Brian refused to use them. He would buy brand new GT lsds and install Cup plates in my product. He's come to see that stuff is long gone and that what we produce now is the best in the business both outlasting and outperforming Porsche's own parts.
Just to clarify, you built my diff for me. He just bench tested to confirm it was tight and functioning well and didn't need any attention.
Another 4.0 and cup LSD here...one of the best upgrades for a 996 GT3. Really wakes them up. Out of curiousity, what is the recommended time out on the 4.0 R&P?
Just to clarify, you built my diff for me. He just bench tested to confirm it was tight and functioning well and didn't need any attention.
I know. What is important is he took it apart and laid eyes on a four year old job. So much false information about the longevity of my parts and for many years I was on this very board arguing with people who were posting,"Brian Copans said..." as if his occasional exposure to my product was more legitimate than my thousands of diffs in the field. You see to many I can't be trusted to speak honestly about something I profit from. I'm really happy you posted. It validates me and my product independently.
Appreciate this post. Andy, one bit of feedback I'd like to hear is about the "seat of the pants" improvement in straight line speed/acceleration (for the guys like me who use their cars primarily as a fun and unique street car and who don't car about shaving tenths at a track). Would be interested in your thoughts on that, as doing a 4.0 rp or even the 3.89 effectively increases the torque of the car far beyond what can be achieved with any other "bolt on" type mods.
4.0 r/p 3rd gear trq feels like 2nd gear. 1st gear is very short. Excellent for tight technical tracks when stock 3rd felt too long. You lose top end speed but you'll won't those speeds on a track. Definitely a seat in your pants feeling going shorter r/p. Mike
06-02-2017, 12:19 PM
Gearing Change - My experience
