I think on an episode of Trucks they showed a 15sp gearbox. The thing was like the size of welll you get the idea. But they need those gears since they need to stay at peak tq when pulling a couple of tons and you get peak at 1000rpms. I doubt they'll ever go more then 6gears in a car MT since ppl would't drive it due to insane amounts of shifting.
I don't think our cars will need 8 speed manual transmissions. A 6 speed manual transmission is good enough, we don't have very powerful engines, so eight speed will be a waste. CVTs are nice and smooth but they tend to let the engine run at high RPM and it can only handle V6 and four cylinder engines for now.
I think the 6-speed will be about the limit, since any more may help in fuel economy, but shifting 6 times (or more) just to get to highway speeds won't appeal to most MTX drivers.
The 7- or 8-speed ATX may become more commonplace. It'll help to better acceleration and fuel economy for ATX models, since, in general, they suffer from more drivetrain loss than MTX.
The sequential-manuals and all the new clutch-less gearboxes are slowly catching on, and I bet they are a blast to drive with, but (IMO) they'll never replace a proper 3-pedal manual. I'm sure I'm not the only one that feels this way.
As for CVT? The verdict's still out on it. Newer Nissans are using more CVTs, and (I think) Ford was to also, but has since scaled back (I know the Fusion was supposed to have a CVT, but was dropped at the last minute). I'm still leary about their long-term durability/longevity, but we'll see...
That'd be crazy if there was more than 6 gears in a manual. Heavier car, more shifting, so more clutch use which could mean clutch life is less. But you would have more flexibility such as shifting from 5th to 8th if fast enough.
8 speed. haha. ATs should just go CVT. 8 spd manual would be terrible. i cant imagine having to shift 7 times to get cruising at 65mph. trucks need the extra gears. personally, i dont want to accelerate 0-60 in 20 seconds because ive gotto shift 4 times.
But you wouldn't want that many in a car. There would be no reason to have more than even 6. Even with that many the gear ratios are so close that you have to shift about as often as you would like. You can stick 8 gears in an Auto because you don't notice the shift changes, but in a Manual you'd be running out of gear every 10mph. I like to shift and all, but that would fucking suck after a while in stop-and-go traffic. You would up up significantly slower because you would have to shift so often. That's why trucks have such a slow time accelerating up to speed, because simply getting up to 30mph can take 8 shifts.
Those trucks only have 5-8 forward gears, and a 2-speed over/underdrive unit between the transmission and rear-end(s).
They have a switch on the shifter that switches the over/under unit back and forth. So when they go through their gears, they flip the switch on every gear. So you have 1, 1-over, 2, 2-over, 3, 3-over, etc. When they aren't towing a trailer, they can skip the overdrive gears.
Some Pick-up truck owners (well the HD trucks with diesels) will install overdrive units in their trucks when towing the bigger campers or other large, heavy-weight trailers. Same thing, they don't have to use them if they are empty.
Thats cool man. I have seen it, but never new that is how they actually shifted like 1, 1 over... Round here we have big old grain trucks with like 2 speed rears. Not sure if they big rigs use that trick or not.
The main reason the trucks have so many gears is that their power band is only several hundred RPM wide. Big diesels are like that. Our gasoline engines have power bands several thousand RPM wide; no need for so many gears.