So what is with the dog clutch transmissions?
So what is with the dog clutch transmissions?
(OP)
And how many of the future multi speed automatic transmissions in planning stages have the planetary and clutch packs
that has been around for the last 60 plus years?
that has been around for the last 60 plus years?
RE: So what is with the dog clutch transmissions?
- Motorcycle transmissions, ALL of which use dog-clutches and have done so pretty much forever?
- Aftermarket, generally rally-car, manual transmissions that use dog-clutches in place of synchro units? (these are in no way production transmissions nor will they ever be)
- Tractor-trailer transmissions, which have used dog-clutches forever?
- The ZF 9-speed front-drive transmission, which contains two dog-clutches (and four conventional clutch packs in addition to the lock-up clutch for the torque converter)?
Since you mention future multi-speed automatics, I presume you're referencing the latter situation. The ZF 9-speed has not gone over well; there are many complaints about driveability problems and slow shifting although supposedly these have been fixed (somehow) for 2016; I don't know what they've done inside, but the 2016 transmission has a different part number. The ZF has two awkward shift situations - downshifting from 8th or 9th into 7th or below, and downshifting from any higher gear into 4th or below. Both of those require the engine to disconnect output torque and "match revs" before the dog clutch can be engaged. A really ugly one is 8th into 3rd (e.g. if the driver mashes the accelerator to the floor somewhere near or just over 100 km/h) because then it has to do this rev-matching for BOTH dog clutches. I've driven a car with this transmission and found it to be fine, but I didn't try to intentionally catch it out.
I know a thing or two about the upcoming GM/Ford 10-speed rear-drive because a customer of mine is building parts for those. It contains six conventional hydraulically-actuated multi-plate clutches, in addition to the torque converter lock-up unit. This is promising to be very good.
I know there's an upcoming GM/Ford 9-speed front-drive but I don't know anything about it at this point.
The other choice is the dual-clutch transmission which uses manual-transmission synchro units. VW/Audi is likely to continue using them, because they seem to be the only ones who have figured them out properly (and even at that, some people don't like them because they have a different feel). I understand that Ford is going to be discontinuing theirs (Fiesta/Focus) and it will be replaced with some sort of conventional automatic; which one isn't known yet. Hyundai seems to be moving forward with theirs.
A big chunk of the automotive world is set on using CVT, like it or not. I don't like them, but I will grant that in a normal daily-driver vehicle driven by a non-enthusiast, they have become a decent solution.
RE: So what is with the dog clutch transmissions?
je suis charlie
RE: So what is with the dog clutch transmissions?
RE: So what is with the dog clutch transmissions?
Many of the new 7-8-9 speed autos have shift ranges that leave them hesitating and hunting for the correct shift. It is just that the ZF does it at a very noticeable speed.
My daughter worked at Allison while they were developing the new 10 for over the road trucks. A lot of broken pieces along the way (and broken budgets also).
They go back to these designs because they are robust and they work.
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P.E. Metallurgy, Plymouth Tube
RE: So what is with the dog clutch transmissions?
If you want a reliable CVT just go with a multi element torque converter, and tune the lockup clutch to better synchronize with shifts and not to go into torque converter mode so much. Initial cost of a normal automatic is more but if it is more durable its a huge savings in recalls and warranty work.
RE: So what is with the dog clutch transmissions?
Going to go ahead and disagree with that.
The Ferraris, Porsches, and Lamborghinis of the world have used pretty superb electronically controlled manuals for quite some time- the only thing keeping them from being more common has been cost, which is coming down.
That's not to say that a 'traditional' automatic is ever going to be obsolete, or is ever going to be a smaller part of the market- but the technology is going to continue to develop for both systems.
RE: So what is with the dog clutch transmissions?
The only mass production automotive transmission that I know of that uses dog clutches, is the ZF 9-speed transverse.
RE: So what is with the dog clutch transmissions?
You apparently hate CVT transmissions for some reason and believe they are completely unreliable. But, a few manufacturers have been selling them for many years now and they appear to still be doing well at their business with no indication they are going to drop them. So, you really need to put up some hard data showing how they are not reliable if you want anyone to take you seriously. Actually, you seem to think that any transmission not using clutch packs is inferior and will never make it in the marketplace.
I expect to see the popularity of computer shifted manuals and the use of dog clutches (since the computer can shift without a synchro) to increase in the quest to build vehicles that can meet the ever increasing fuel mileage standards.
RE: So what is with the dog clutch transmissions?
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P.E. Metallurgy, Plymouth Tube
RE: So what is with the dog clutch transmissions?
Be aware that Nissan has had some teething pains with the CVTs in some of their product lines, and I understand that it gets expensive when the CVT does take a dump (last I knew, replacement was the only method of repair).
Aggressive torque management when the drive pulley is at its smaller diameters isn't going to be terribly appealing to those who are looking for high performance at low(ish) road speeds.
Norm
RE: So what is with the dog clutch transmissions?
If this was my car, I'd be complaining. Fortunately, it only needs to make it another 10 miles or so back to the rental agency, at which point it becomes "someone else's problem".