Newer auto transmissions

[CBR.worm]

I have actually wondered if some of these 6 and 8 speed transmissions are actually CVT's with preset ratios and a torque converter.

I know it's a stretch, but it seems like with the exception of DSG and SMG type things the transmission housings aren't big enough for all the extra planetary gear sets.

It does seem like modern elecronically actuated valve bodies have got to be a lot simpler than days past when they relied on regulators and springs and balls, etc.

 

[XS650]

Originally Posted By: CBR.worm
I have actually wondered if some of these 6 and 8 speed transmissions are actually CVT's with preset ratios and a torque converter.

I know it's a stretch, but it seems like with the exception of DSG and SMG type things the transmission housings aren't big enough for all the extra planetary gear sets.


Nope, they use planetary gear sets.
The examples I found
4 speed = 2 planetary sets
6 speed = 3 planetary sets
8 speed - 4 planetary sets

 

[Gary Allan]

Originally Posted By: alphasparky353
Is it just me, or automagic transmissions getting very very complicated? 6 speed, 8 speed, duall clutch....kinda scary out of warranty...


What decade did you wake up in Rip Van Winkle? Automatic transmissions haven't been simple since the 70's where they handled power that is only dreamed of in a common passenger car. After about 2 decades of fixing the flaws ..they managed to make them reliably complex. Since they're now stable, it must be time to reinvent the sophisticated wheel.

 

[JHZR2]

Kind of on the note of the CVT in disguise post above, my main concern is kind of the same... Power density. There really isnt a huge amount of additional space in any modern car compared to any other car. Yet we are cramming more and more gears, and other stuff in there. What gives?

We are getting ever-more powerful engines, all the time, and the ATs get more gears in roughly the same package. At some point the contact surfaces, etc. need to shrink, which can only have a negative effect on life using current standard materials. Of course advanced fluids are being used, but how much does that actually help the mechanics of it?

 

[rslifkin]

It works just fine when the typical driver who never presses the gas pedal more than 1/3 of the way down is driving. When they get driven hard, it's anybody's guess how well they'll hold up.

 

[SteveSRT8]

just watch. Dozens of new makes and models are using the fancy ZF 8 speed. It's very trick and can even stand up to real horse pressure.

No cvt's in any high torque applications. Can't take it.

 

[OVERKILL]

Unless you are Nissan, and then the regular transmission can't take it either

 

[The Critic]

The newer Nissan CVTs in the V6s have been holding up great. That is, 07 and newer with the 6th or 7th generation ?? units.

 

[OVERKILL]

I was just poking a little fun at the GT-R transmission actually

 

[The Critic]

That ain't a regular transmission. That's a Borg Warner DCT!

 

[exranger06]

Back in the mid-90s, Ford converted the 4-speed 4r55e transmission into a 5-speed 5r55e (have one in my Ranger). The two are almost identical, and IIRC, completely interchangable. The way it works is instead of shifting from 1st-2nd-3rd-4th, it applies overdrive to 1st gear and goes 1st-(1st-OD)-2nd-3rd-4th, essentially creating a fifth gear. Just about everything mechanical is exactly the same, the only difference is the computer controlling it. I wouldn't be surprised if a lot of these 7 and 8 speed transmissions do something similar.

 

[Gary Allan]

They've already sorta done that, haven't they? I mean, don't some transmissions use the lock up converter as intermediate (effective) gear changes? Turns a 4 speed into an 8 range trans??

I would think that one could merely have progressive locking converters with various stall speeds and have an engine with a very narrowly tuned power band ..and manage the full range of sensible operation. I dunno what the hp penalty is, but it could manage with a much smaller engine ..or so I would imagine. So it may not be particularly efficient but may be economical with sensible performance characteristic.

I think we need more MIG designers getting advanced manufacturing access. We must keep finding F22 wannabe's

 

[SteveSRT8]

Mercedes has had infinitely variable lockup for over a decade. Works in any gear but first and reverse.

It works great with huge torque capacity. Like 500 foot pounds!

Actually a variable displacement pump is one of the coming innovations. Cuts the parasitic drag, a lot like GM's new Ecotec with variable displacement oil pump.

Too many of us are assuming that all manufacturers make similar transmissions. They don't. There will be a HUGE wave of standardization across brands as ZF and others "gear" up for America and other markets.

 

[440Magnum]

Originally Posted By: Gary Allan
They've already sorta done that, haven't they? I mean, don't some transmissions use the lock up converter as intermediate (effective) gear changes? Turns a 4 speed into an 8 range trans??


First such application I know of was the 1989 Chrysler 41TE (first called the A604), although others may have done it before that in lower production volume units.

Partial lockup began in 2nd gear, with progressively more lockup applied in 3rd and 4th (which of course ended in 100% lock).

That one function was the genesis of ATF+3 (aka type 7176), because the TC clutch would tend to shudder at high lock percentages. The sensation was like driving over a gigantic washboard. Earlier automatic trans TC clutches that were either engaged or not simply passed quickly through the "shudder zone" on the way to full lock so shudder virtually never happened, but the 41TE would hang out for several seconds in a regime where shudder was likely. ATF+3 twiddled the static and dynamic coefficients of friction to be closer together so there wasn't a sharp spike in friction coefficient just as slippage stopped, which prevented shudder.

 

[CBR.worm]

I had an A604 in a 3.0 '89 grand voyager. I heard they were problematic, but ours was perfect until the head gasket in the second motor blew at. 289k. And we towed a boat through the mountains with it regularly.

We had a great one. The AC, not so much.

Proper oil made a huge difference in shift quality. Seems like there were a number of software updates as well.

 

[440Magnum]

Originally Posted By: CBR.worm
I had an A604 in a 3.0 '89 grand voyager. I heard they were problematic, but ours was perfect until the head gasket in the second motor blew at. 289k. And we towed a boat through the mountains with it regularly.

We had a great one. The AC, not so much.

Proper oil made a huge difference in shift quality. Seems like there were a number of software updates as well.


The A604/41TE was definitely put into production before it was ready. They had TONS of problems through 1992, lots of problems through about 2000, and finally got pretty reliable around 2003 or so. It PO'd a lot of consumers and put them off Chrysler minivans, but the truth is that it was a very groundbreaking design and totally new philosophy of how to operate an automagic. Everyone does it pretty much that way now, and with much better finesse. But back then it was a big and fundamental change to eliminate all the overunning clutches, eliminate all the bands, shrink everything down, and control it all with software.

 

[CBR.worm]

It truly was amazing at the time.

Once it adapted to your driving style (or did we adapt to it?) it worked incredibly well. I drive different rental cars every week, many of them do not shift as well as those did. It was the only domestic auto that I have ever really been a fan of.

 

[Gary Allan]

Quote:
Partial lockup began in 2nd gear, with progressively more lockup applied in 3rd and 4th (which of course ended in 100% lock).


Never quite saw that as a reliable process. I can't imagine (I'd never pull that one out of my behind in a million years) a "slipping clutch" being used as a virtual variable gear. Too much fine management and too much wear. It would, naturally, provide those velvety smooth shifts that we all pounded our fist on the engineer's desks for ..but ..hey, they're getting paid the big bucks. Simple 6 or 8 range transmissions should have managed well enough, or so I would have thought.

I do admit that my son's 96 Caravan has totally invisible shifts for the most part. I just don't see it as an issue one way or the other. What's it for, providing a better platform for putting on makeup on the way to work?

 

[Gary Allan]

Quote:
Mercedes has had infinitely variable lockup for over a decade. Works in any gear but first and reverse.


Is that ala Chrysler method of transitioning?

 

[SteveSRT8]

Originally Posted By: Gary Allan
Quote:
Mercedes has had infinitely variable lockup for over a decade. Works in any gear but first and reverse.


Is that ala Chrysler method of transitioning?


Wish I knew what you mean.

But in my car they did copy the trans design directly from Mercedes. In fact, my cars trans and rear end have 'made in Germany' stamped on them.