Ford PowerShift Transmission Fiascorama Extravaganza - Page 1
Forum section: electronics / general

author: soldar
author_rank: Super Contributor
timestamp: July 29, 2019, 09:37:24 am
content: I've kind of been following this for some time now but never really understood the technical part of the problem.This reminds me a lot of the Boeing 737 Max problem. The product needed to be rushed to market. Half way through the design the engineers said "this won't do" but management said "we can't turn back and start over now, we don't have that kind of time, so just get it out the door as best you can and we'll find a fix later". By the time Ford realized there was no possible fix they had already sold more than half a million units. While they could they bullshitted customers, they gave them the runaround, etc. The mess has resulted in a class action lawsuit which is under way.OK, so that part I think I have the big picture covered. What I don't quite understand is the technical part because it is not talked about much. Double clutch gear boxes are common in other cars and work well so, obviously, mistakes were made in the design. What are the causes that make these boxes bad? What is the design flaw? I mean, a gear is a gear and a clutch is a clutch, it's not like Ford invented all this. What's the problem?https://www.youtube.com/watch?v=KBfVqdo576w?t=0https://www.freep.com/in-depth/money/cars/ford/2019/07/11/ford-focus-fiesta-transmission-defect/1671198001/https://www.youtube.com/watch?v=5WDswUZcit8?t=0

author: SteveyG
author_rank: Unknown
timestamp: July 29, 2019, 10:15:08 am
content: Quote from: soldar on July 29, 2019, 09:37:24 amThe main difference is these gearboxes produced by Getrag use dry clutches in the interest of efficiency. Wet clutches add drag to the drivetrain so therefore don't achieve the same levels of efficiency.The downside of the dry clutch is there is no rotational coupling until the clutches engage, thus the actuators and control system has to be very accurate to offer smooth shifting. Wet clutches offer better coupling prior to engagement so they can tolerate poorer control.The problem is mainly the American market which is used to torque converter type automatic transmission. The dual clutch transmissions are already badly received in that market.

author: soldar
author_rank: Super Contributor
timestamp: July 29, 2019, 10:19:15 am
content: Quote from: SteveyG on July 29, 2019, 10:15:08 amWhat's the problem with using dry clutches? All my (manual box) cars have had dry clutches and worked fine.

author: SteveyG
author_rank: Unknown
timestamp: July 29, 2019, 10:38:32 am
content: Quote from: soldar on July 29, 2019, 10:19:15 amThe problem is the controller and actuators they are using are based on those from their wet clutch boxes. They don't appear to be suitable for the job.Manual gearboxes are a separate entity.I've driven with the gearbox in question and it's fine, but it doesn't feel as smooth as a torque converter.The experience in the UK is that this gearbox has no future maintainability. When the clutches wear out, no one is equipped to exchange them so the cars are being scrapped or people are forced to pay many thousands for a new gearbox.

author: voltsandjolts
author_rank: Unknown
timestamp: July 29, 2019, 11:18:12 am
content: Is this another dry clutch versus wet multi-plate clutch thing, like the VW/AUDI gearbox debacle?Wet multi-plate seems to be much more reliable, AFAIK......(touches wood...)

author: SteveyG
author_rank: Unknown
timestamp: July 29, 2019, 11:22:03 am
content: Quote from: voltsandjolts on July 29, 2019, 11:18:12 amYes. Although the reliability is basically the same, just no one can do a clutch replacement on these gearboxes. I've seen DSG boxes needing replacement clutches at 40k miles

author: coppice
author_rank: Super Contributor
timestamp: July 29, 2019, 11:28:02 am
content: Quote from: soldar on July 29, 2019, 09:37:24 amDouble clutch gearboxes seem to be settling down now, but Ford is not the only company to have serious problems with an early version of a double clutch gearbox. Early adopters usually end up as long term testers of new technology, but sane companies avoid introducing major new technologies on their highest volume products.Its interesting to compare car adverts in Europe and Asia. In Asia every slightly revised car gets advertised as "the all new....". In Europe people are so jaded about problems in new designs that car makers tend to emphasis the solid history their new product is built upon.

author: SteveyG
author_rank: Unknown
timestamp: July 29, 2019, 11:40:01 am
content: Quote from: coppice on July 29, 2019, 11:28:02 amFord (and Volvo) have been using Getrag wet dual clutch automatics for over a decade with no issues. The dry clutch is a more recent attempt to improve economy, but only made it to a very limited number of vehicles (in the UK at least) due to the low power handling capability.

author: amyk
author_rank: Super Contributor
timestamp: July 29, 2019, 12:07:44 pm
content: ZF makes some of these new type of transmissions for buses and they are horrible to ride in. There is a torque converter but it locks up almost immediately, giving very jerky and slow acceleration complete with throttle dips like a manual transmission would shift. Normal automatics can keep the engine at the RPM for peak torque when they shift, making for faster and smoother acceleration.

author: coppice
author_rank: Super Contributor
timestamp: July 29, 2019, 12:15:44 pm
content: Quote from: SteveyG on July 29, 2019, 11:40:01 amPretty much every double clutch gearbox has had at least one problem due to marketing departments. They don't want to tell the customer that they shouldn't drive their new double clutch car like their old torque converter car. The result for many people has been early clutch replacement due to them allowing their car to creep for long periods in heavy traffic, as they always have, with the clutches slipping and wearing. People who need to regularly crawl on slopes (like those with inclined drives) seem to have suffered a lot through this.

author: coppice
author_rank: Super Contributor
timestamp: July 29, 2019, 12:17:57 pm
content: Quote from: amyk on July 29, 2019, 12:07:44 pmThat sounds like bad implementation. The smart systems now tie the gearbox control into the engine control system, so they can do rev matching as they change gear.

author: soldar
author_rank: Super Contributor
timestamp: July 29, 2019, 12:44:05 pm
content: OK, so the answer is "good gears, bad clutches". Wet or dry issues aside it seems to me the clutches then are just too small for the task because I have seen dry clutches on big trucks and handling a lot more power. So the clutches are too small for the power being handled? is that it?

author: coppice
author_rank: Super Contributor
timestamp: July 29, 2019, 12:56:17 pm
content: Quote from: soldar on July 29, 2019, 12:44:05 pmThat seems to be a major factor in the wear and tear issues related to creep. A wet clutch has much better cooling. A dry clutch can get super hot creeping up a slope unless its quite substantial. "This is not a torque converter gearbox" said loud and clear might help a lot.

author: NiHaoMike
author_rank: Super Contributor
timestamp: July 29, 2019, 01:09:56 pm
content: Quote from: coppice on July 29, 2019, 12:15:44 pmHyundai has an innovative solution to that problem in their Sonata Hybrid by adding an electric motor to one of the intermediate shafts between the clutch pack and transmission itself.

author: soldar
author_rank: Super Contributor
timestamp: July 29, 2019, 01:12:46 pm
content: Well, yes, I understand. You can burn the clutch with a manual transmission if you set yourself to it but this problem with Ford does not seem to be a few people who were driving badly. It seems like everybody and his brother were having problems so it does seem like the clutches were just under-engineered. And why would they choose dry clutches if the knew wet clutches would work better?

author: SteveyG
author_rank: Unknown
timestamp: July 29, 2019, 01:15:43 pm
content: Quote from: soldar on July 29, 2019, 12:44:05 pmNormal clutches on a manual gearbox are a completely different entity, so shouldn't be compared.There were some automatic gearboxes that were a just manual gearbox with a mechatronic unit (I think the BMW E60 M5 had one of these), but otherwise a human manually controlling a clutch will give very different results.We are taught not to ride the clutch excessively, however someone driving an automatic has no idea what the gearbox is doing. As mentioned, people creeping in traffic are the worst to suffer with the dry dual clutch boxes. The answer may be, good clutches, good gears - but not enough of them...Too many variables for different driving styles, engine types and emissions targets.

author: SteveyG
author_rank: Unknown
timestamp: July 29, 2019, 01:16:25 pm
content: Quote from: soldar on July 29, 2019, 01:12:46 pmEfficiency, cost etc. already mentioned.

author: voltsandjolts
author_rank: Unknown
timestamp: July 29, 2019, 01:43:25 pm
content: Quote from: SteveyG on July 29, 2019, 01:15:43 pmNeed to take cabin air from the clutch bell housing so you can smell when you are torturing the clutch.

author: soldar
author_rank: Super Contributor
timestamp: July 29, 2019, 07:12:41 pm
content: Quote from: voltsandjolts on July 29, 2019, 01:43:25 pmThey used to teach us to not ride the clutch and we wouldn't ride the clutch.Now everything is supposed to be fool-proof and yet, as someone said, "If you make something idiot-proof, someone will just make a better idiot."

author: jmelson
author_rank: Super Contributor
timestamp: July 29, 2019, 07:37:22 pm
content: Quote from: NiHaoMike on July 29, 2019, 01:09:56 pmHonda has been using a wet-pack clutch and variable speed drive in their civic hybrid for over a decade. It works pretty well. They call the clutch a start clutch, and it is used to get the car rolling at the lowest speed the VSD can handle, which is apparently VERY slow, like below walking speed. From there on up, the clutch stays fully engaged and the VSD slides to control engine speed. The only place the clutch is a bit annoying is when backing up a hill, then it acts like a guy who's just learning to drive a stick shift. There is no torque converter, and either another clutch or sliding gear or something for reverse.if not abused, the VSD/clutch generally lasts the life of the car. You DO have to change the transmission fluid regularly.Jon

author: schmitt trigger
author_rank: Super Contributor
timestamp: July 29, 2019, 08:11:08 pm
content: Welcome to the brave new world of stock market capitalism, whereas the short-term stock valuation (and its corresponding management bonuses), have priority above anything else.From the technical point of view, unfortunately there are precious few technical details, other than its development time was too short for the price and performance requirements.Having been involved in similar, although at a far smaller scale, on a previous job, I know how it could have unfolded: Management pressured to rush into production a device which was not properly validated. Long story short, the product eventually had to be recalled. Looking for whom to place the blame followed, usually the manufacturing facility.

author: edy
author_rank: Super Contributor
timestamp: July 29, 2019, 08:49:13 pm
content: Wow, I just read that FREEP article and it's pretty shocking! I had a GM Buick Century back in the 90's and I remember it didn't even last 10 years before I would occasionally get transmission "slippage" into neutral. That is, I would be going up a hill somewhere on a highway when all of a sudden the transmission would "slip" into neutral and my engine would all of a sudden RPM up against no resistance. Never had any issues on flat terrain or going down hill, because the engine torque/transmission torque differential must not have been very different. However, when pushed too hard by the engine to keep torque on the wheels.... the transmission slipped. NOT A GOOD THING!It is also dangerous as you are driving along and every time you hit a valley/hill you either accelerate like crazy down the valley so you can ride up the upcoming hill by mostly coasting, or you need to be careful how much GAS to press lest you risk "slipping" your transmission, either way you end up decelerating each time you try to climb any grade while 18-WHEEL TRUCKS are right up your tail or flying by you and honking the horn at you.Fairly shortly after that started happening, I sold the car for parts and was glad to be rid of it. I then bought a Nissan Sentra with a CVT and felt like I was driving a "rubber band" car, it was strange but it did accelerate like a demon. Then moved on to Honda CR-V which is my current daily driver... not particularly spunky in the acceleration department but it gets me from A to B. If I was to do it again, I might have bought a Subaru with a manual gearbox but then nobody in my family would be able to drive my car and the resale options/value would be dicey.At least the CR-V I can offload in a jiffy for minimal depreciation, but it's not exactly fun to drive.

author: John B
author_rank: Frequent Contributor
timestamp: July 29, 2019, 08:59:25 pm
content: Quote from: soldar on July 29, 2019, 07:12:41 pmDesign decisions can be strange. There's an emphasis on making gearshifts as seamless as possible, to appeal to the middle of the road customer, but with that comes some trade-offs in mechanical wear.Even 20 year old torque converter planetary automatics have these design compromises. Some slightly overlap the engagement of the clutch bands to make the shifts smoother at the cost of wear and heat generation.

author: Gyro
author_rank: Super Contributor
timestamp: July 29, 2019, 09:15:00 pm
content: Quote from: NiHaoMike on July 29, 2019, 01:09:56 pmYes, a Hybrid motor is the perfect solution to DSG and dry clutch.In the drive train used in the Kia Niro and Hyundai Ioinq, there's a dry clutch between the engine and the electric motor. The motor can creep the car all day if necessary, even it it needs to start the engine with the clutch disengaged to charge the battery (via the HSG). Once the shaft speed sufficient, it can start the engine, synchronise it, and engage the clutch with virtually no slip - apparently the engagement time is around 0.6 seconds.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: July 29, 2019, 09:35:28 pm
content: As an American used to torque converters, what is the proper way to drive a dry double clutch automatic transmission?When creeping along in rush hour traffic, what does one do to avoid abuse of the transmission?When crawling up a steep grade behind a heavily laden truck doing 35 km/hr and no passing zones?If the design cannot be used in these and other situations it isn't fit for purpose. Telling me not to ride the clutch when there is no clutch pedal is a marketeers kind of response. Staying stopped until a sizeable gap has developed isn't a solution. In any heavy traffic situation I have ever been in that would just result in the gap filling with vehicles from other lanes while you are being serenaded by the horns of those behind you.

author: soldar
author_rank: Super Contributor
timestamp: July 29, 2019, 09:49:57 pm
content: Quote from: CatalinaWOW on July 29, 2019, 09:35:28 pmFrom everything we're seeing the answer is "don't!". Don't even think of buying one!

author: bdunham7
author_rank: Super Contributor
timestamp: July 29, 2019, 10:13:03 pm
content: Quote from: soldar on July 29, 2019, 09:37:24 amThe technical issues really boil down to bad implementation (quality) rather than a single basic design inadequacy--although the dry dual-clutch idea has inherent issues of its own. This reminds me of the all-electronic non-overrunning Chrysler Ultradrive/A604 that they introduced in 1989 that had failures requiring replacement by the truckload. I suspect the issues are similar--poor quality control and cheapened parts due to cost control rather than any real issue with a novel design. The Focus trans has multiple issues that aren't explained simply by the inherent issues with the dry-dual-clutch design. The have seal leaks and mechanical control problems. They don't just slip and judder from stops, they quit working altogether. They suddenly engage and disengage when they shouldn't. They don't get the right gear. They fail shifts and you end up coasting for a while. They leak, and then they leak again. As with the Ultradrive, the design can work well if it doesn't break.IMO, the problem is that a proper quality transmission of this design would actually be much more expensive than a conventional automatic because of the mechanical controls required to make it operate--it has to physically select the 6 gears and then modulate the clutch controls. Transmissions are expensive as it is, so I'm sure they didn't want to spend MORE than they were spending on the old TC-fronted automatics, so they came out with an untested, cheapened version and not surprisingly, it was a POS. All in all, sadly, a colossal screw up that really doesn't have a fix. Even sadder, I own Ford stock and a 2014 Focus--but mine is the Electric, so no trans issues yet.

author: Bassman59
author_rank: Super Contributor
timestamp: July 29, 2019, 11:14:10 pm
content: Quote from: SteveyG on July 29, 2019, 11:22:03 amI don't know whether the VW DSG transmission uses a wet or dry clutch or what. All I know is that the cost of routine maintenance at 40,000 miles was such that I wanted to part of it.

author: amyk
author_rank: Super Contributor
timestamp: July 30, 2019, 12:39:12 am
content: Quote from: coppice on July 29, 2019, 12:17:57 pmThe "rev matching"isthe problem --- the older automatics, like Allisons and Hydramatics, can shift under full power, giving smooth uninterrupted acceleration. The new "computer controlled manual transmissions" can't, making for a much rougher and slower acceleration more like a human driving a manual transmission.

author: John B
author_rank: Frequent Contributor
timestamp: July 30, 2019, 02:21:51 am
content: I remember a comment from an automotive engineer who stated that the shift mapping, and all the associated variables of timing retardation, line pressure control etc, was far more involved than engine mapping. It wouldn't be surprising to find that companies just run out of time and budget to sort out the transmission. Not that it's an excuse, but an explanation. Even a common transmission will require tweaking between different engine pairings.

author: Circlotron
author_rank: Super Contributor
timestamp: July 30, 2019, 02:43:38 am
content: Quote from: John B on July 29, 2019, 08:59:25 pmThat's where the General Motors Turbo 300, 400 and 700R4 series autos were brilliant. No overlap. When the next higher gear comes in it simply overruns the previous gear courtesy of a sprag. There is no lower limit to shift speed that will cause flaring. Just a clutch pack gradually squeezes up and takes over. That's my rough explanation at least. Anyone is welcome to correct me.

author: bdunham7
author_rank: Super Contributor
timestamp: July 30, 2019, 08:31:19 pm
content: Quote from: Circlotron on July 30, 2019, 02:43:38 amYou've got it right--the THM400, etc were fully overrunning, but the downshifts are what actually benefited the most. Most other transmissions were overrunning for at least the 1-2 shift, one important reason for this is to prevent the coast-up lurch as you come to a stop sign. With an overrunning gear, you can shift into first at any time and there is no back torque. With a non-overrunning design, it is difficult to time the coast-down shift-down points so as to both keep it smooth and not get caught between gears when the driver goes again.

author: amyk
author_rank: Super Contributor
timestamp: July 31, 2019, 03:11:25 am
content: The 2-3 shift on the 700R4 does involve releasing a band and applying a clutch, so if they overlap it becomes overdrive (4th), and if they both release then the engine flares up.(I have a 700R4, would've gotten a 4L80 because they're stronger but didn't find a fully mechanical conversion for them at the time. If I didn't need overdrive I would've used a TH400.)