GT4 final drive discussion
#256
Again, I can see where the gearing in the GT4 is fine for track use and possibly Germany...but I felt the GT4's gearing let the car down on the street in the U.S. and still do. Maybe fixing the flat spot in the powerband would help, or adding hp as some here have stated. But after selling my GT4 and then logging nearly 10,000 miles in a 991.2, I find the latter has perfect gearing for the street and that I'd love a GT4 with 1-5 from the 991 and 7th from the 991 in 6th for freeway cruising.
Wow. So 2nd gear in the GTS is a little closer to 1st, but overall all the gears are taller and the spread is wider as well. Using the GT4 power, you don't even make it out of 5th! I didn't even graph 7th as the sheet is only configured to go up to 6th, but no worry since we didn't even get there. You're saying you liked the gearing better, but it turns out what mattered here most was the power.
For a real comparison you'd need to add the power curve for the 991.2, but that's more work than I care to take on myself.
I suspect you would be pretty happy with a different final drive in the gt4, gearing-wise. It would "feel" more like the 991.2 as far as shifting.
#257
Rennlist Member
Wow. So 2nd gear in the GTS is a little closer to 1st, but overall all the gears are taller and the spread is wider as well. Using the GT4 power, you don't even make it out of 5th! I didn't even graph 7th as the sheet is only configured to go up to 6th, but no worry since we didn't even get there. You're saying you liked the gearing better, but it turns out what mattered here most was the power.
I can see where I might like a shorter final drive in a track-dedicated GT4—but most people I know with GT4s who track them usually have to drive them a couple of hours (or more) to and from the track. So a shorter final drive exacerbates the freeway cruising issue...more revs = more fuel for no good reason, more wear & tear on all engine parts, and more subtle stress on long drives. It's actually really hard to overstate how nice the gearbox in the 991.2 Carrera is. Not quite as nice a shifter as the GT4, but the ratios feel better chosen 1-6 and 7th is such an ahhhhhhh on long trips. In all but the shift action, it's a vastly superior contraption in use. That said, I could easily sacrifice 6th gear—and would if there was some way to import the philosophy of 1-5 and 7 from the 991 into the 981 GT4 gearbox. For use here in the U.S., anyway.
I know this will be the contrarian position in this thread—it is a forum, after all—but I view installing a shorter final drive in the 981 GT4 as a band-aid fix for a street car...one that may leave some customers very unhappy in the long run. Yes, the upside is it preserves the gear splits and improves effective torque where we all want it (out of turns), and fine if it fits someone's use/needs and they don't care about turning 3700-4000 rpm on long freeway drives. But my worry is that some will make this switch and regret it once they have to live with it.
Now, if I was trailering a GT4 to and from the track and looking for performance, I think you are precisely right...if the track(s) I favored worked well with the shorter final drive. But if I was trailering a GT4 to and from the track, it would have a six-speed PDK gearbox.
pete
#258
You are right, the main value is for the track. There's little interpretation required.
For street use, however there is still some value. Reduce the redline and pay attention to the speed range per gear bar chart. That will give you a sense of the gearbox action.
but in a street car/fun car, seat of the pants observation
And my observation is that the gearing and powertrain in general of the base 991.2 Carrera MT along a back road shred my old GT4 both in terms of fun and performance. YMMV, and that's okay.
If directed at me, yup, can't agree more. It's not something that can be disagreed with as its your personal observation, and nothing I presented here challenges that. Since I didn't do the power graph for a 991.2, the difference in gear ratio don't reflect the reality, as I made clear. The point I was making is that it's not just gears. I demonstrated that if you just plopped the 991.2 gears into the GT4, it would be worse, not better.
I know this will be the contrarian position in this thread—it is a forum, after all—but I view installing a shorter final drive in the 981 GT4 as a band-aid fix for a street car...one that may leave some customers very unhappy in the long run. Yes, the upside is it preserves the gear splits and improves effective torque where we all want it (out of turns), and fine if it fits someone's use/needs and they don't care about turning 3700-4000 rpm on long freeway drives. But my worry is that some will make this switch and regret it once they have to live with it.
If the freeway cruise is an important factor, then you are right, a shorter diff ratio is a terrible bandaid. Myself, I use the GT4 purely for recreational/pleasure drive and would just suck it up for the rare long cruise.
Last edited by mousecatcher; 08-12-2018 at 11:57 AM.
#259
Rennlist Member
^ All good, mousecatcher, and wasn't "after you" per se—just offering a different point of view, and one that might prevent someone from ending up with a GT4 they hate living with on long freeway hauls. If that's a non-issue for you, then your position makes sense to me, and I might even share it. My GT4 had to do everything, so long freeway runs were part of its use. And, even with the stock gears, I found sixth far too short with real consequences (noise, fuel consumption, and to a lesser extent wear/tear).
So making sixth even shorter shorter would be a nonstarter for me. But it sounds like we are in agreement on this point. Actually agree with all your points except exactly what can be charted and is inevitable: what a shorter effective final drive will do to (already high) revs at freeway speeds in sixth gear. That's it. As for just adding 991.2 gears to a 981 6MT, that's not what I meant. I'd be intrigued by those effective ratios...is all. What's in the GT4 isn't great, else we wouldn't be here. Actually, the shorter effective final drive would be great for me (and, I suspect) a lot of customers out there if it could somehow be partnered with a taller sixth.
Cheers,
pete
So making sixth even shorter shorter would be a nonstarter for me. But it sounds like we are in agreement on this point. Actually agree with all your points except exactly what can be charted and is inevitable: what a shorter effective final drive will do to (already high) revs at freeway speeds in sixth gear. That's it. As for just adding 991.2 gears to a 981 6MT, that's not what I meant. I'd be intrigued by those effective ratios...is all. What's in the GT4 isn't great, else we wouldn't be here. Actually, the shorter effective final drive would be great for me (and, I suspect) a lot of customers out there if it could somehow be partnered with a taller sixth.
Cheers,
pete
#261
#262
Rennlist Member
Tried a ring and pinion only once on a dual purpose car. After a Cincinnati/Road Atlanta round trip the R&P came out and I went with a set of short gears.
#264
Rennlist Member
I'd still worry about the strength/longevity of the short R&P in a GT4.
#265
Rennlist Member
Still think the "money" setup would be effectively similar gearing to 991.2 S/GTS/T transmission's 1st through 5th gear + 7th. Add that along with exhaust + tune and I suspect the GT4 would really wake up.
#267
Nordschleife Master
Be sure to buy a fixed 3rd gear while you are at it. 3rd gear should be part of every ring and pinion job a GT4 owner does and factored into the cost if comparing gears versus CWP costs.