The Truth About Cars » automatic transmission The Truth About Cars is dedicated to providing candid, unbiased automobile reviews and the latest in auto industry news. Sun, 27 Jul 2014 11:00:20 +0000 en-US hourly 1 The Truth About Cars is dedicated to providing candid, unbiased automobile reviews and the latest in auto industry news. The Truth About Cars no The Truth About Cars (The Truth About Cars) 2006-2009 The Truth About Cars The Truth About Cars is dedicated to providing candid, unbiased automobile reviews and the latest in auto industry news. The Truth About Cars » automatic transmission SAE Paper Summary Leaking 2015 Corvette’s 8 Speed Auto Gets Redacted Tue, 10 Dec 2013 13:00:19 +0000 2014-GM-Eight-Speed-Automatic-Transmission

It’s not known if the leak was intentional or not, but the summary of a paper initially published by the Society of Automotive Engineers, since taken down from the SAE site, says that a new eight speed automatic transmission, given the designation 8L90 by General Motors, will be introduced in the 2015  Corvette, on sale next fall. The all-new 7th generation Corvette is currently offered with GM’s 6L80 six speed automatic and a seven speed manual gearbox. The 8L90 is described as being designed for rear-wheel-drive applications and variants will likely be used in GM’s fullsize pickups and in rear wheel drive Cadillacs.

The 8L90 has about the same overall dimensions as the 6L80, and is said to be able to handle up to 737 lb-ft of torque. It has a shorter first gear for better launch acceleration, an overall ratio spread of 7.0 and three speed sensors for better shift response. Other benefits are said to be better fuel economy, improved performance and a quieter car with improved NVH levels. The current automatic C7 is rated at 28 mpg on the highway and it’s possible that with the new eight-speed it might be able to achieve 30 mpg. Of course, at EPA “highway” speeds, the 455 hp LT1 in the Corvette is more or less loafing along.

Also new for the 2015 model year will be a Z06 version of the new Corvette that will be introduced in about a month at the North American International Auto Show in Detroit. Previous generations of the Z06 were stick only, but now that you can’t buy some Porsche and Ferrari models with a manual transmission, it’s possible that the C7 Z06 may offer the 8L90.

The full SAE paper will be available in April. Fortunately, before the SAE pulled it, someone at managed to preserve the text:

General Motors Rear Wheel Drive Eight Speed Automatic Transmission
Technical Paper
James Michael Hart, Tejinder Singh, William Goodrich

General Motors Rear Wheel Drive Eight Speed Automatic Transmission General Motors shall introduce a new rear wheel drive eight speed automatic transmission, known as the 8L90, in the 2015 Chevrolet Corvette. The rated turbine torque capacity is 1000 Nm. This transmission replaces the venerable 6L80 six speed automatic transmission. The objectives behind creation of this transmission are improved fuel economy, performance, and NVH. Packaging in the existing vehicle architecture and high mileage dependability are the givens. The architecture is required to offer low cost for a rear drive eight speed transmission while meeting the givens and objectives. An eight speed powerflow, invented by General Motors, was selected. This powerflow yields a 7.0 overall ratio spread, enabling improved launch capability because of a deeper first gear ratio and better fuel economy due to lower top gear N/V capability, relative to the 6L80. The eight speed ratios are generated using four simple planetary gearsets, two brake clutches and three rotating clutches. The resultant on-axis transmission architecture utilizes a squashed torque converter, an off-axis pump and four close coupled gearsets. The three rotating clutches have been located forward of the gearsets to minimize the length of oil feeds which provides for enhanced shift response and simplicity of turbine shaft manufacturing. The transmission architecture features a case with integral bell housing for enhanced powertrain stiffness. A unique pump drive design allows for off-axis packaging very low in the transmission. The pump is a binary vane type which effectively allows for two pumps in the packaging size of one. This design and packaging strategy not only enables low parasitic losses and optimum priming capability but also provides for ideal oil routing to the controls system, with the pump located in the valve body itself. The transmission controller is externally mounted, enabling packaging and powertrain integration flexibilities. The controller makes use of three speed sensors which provide for enhanced shift response and accuracy. Utilization of aluminum and magnesium components throughout the transmission yields competitive mass. The dedicated compensator feed circuit, used in GM six speed designs, was supplanted by a lube-fed design in order to simplify oil routing and enhance shift response. Packaging is within that of the GM 6L80 design, allowing for ease of application integration. The overall result is a robust, compact, and cost effective transmission which offers significant fuel economy and performance benefit, over its six speed counterpart, and shall provide an attractive balance of overall metrics in the automatic transmission market.


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Trackday Diaries: The idiot’s guide to left-foot braking. Mon, 24 Jun 2013 13:15:01 +0000 Picture courtesy the author.

There was some mild consternation among the Best&Brightest when I admitted to left-foot braking the Focus SE in traffic. To a man (or woman), our readers were not pleased at the thought that I might be bumbling along a freeway at ten miles per hour or so, alternately pressing the brake and accelerator with one foot per pedal. One wonders what they might have made of LJK Setright’s famous assertion that he occasionally drove cross-footed, pressing the accelerator with his left foot and the brake with his right, “to ensure that driving is a conscious, not unconscious, activity.”

In any event, I would suggest that there is one scenario where you may left-foot brake, one scenario where you should, and one where you absolutely must not, and I’ve detailed them below.

Before we discuss all the different ways in which you can left-foot brake, let’s make sure we understand how the pedals are “normally” operated in a street car. The driver sits down with his left foot braced against the floor — or the dead pedal, where such a thing can be found. The role of the left foot is important here. Consider this: when a car accelerates, the driver is held in place by the upright portion of the seat. When a car corners, the driver is held in place by the seat bolsters, the seatbelt, or, in worst-case scenarios, by the door and the center console. When a car decelerates, however, what holds the driver’s body in place? A reasonably fit individual might be able to resist 1g of braking force by pressing his hands against the steering wheel; that’s kind of like doing a pushup with your hands close together. Some seatbelts will inertia-lock and hold the driver in place, but that’s not a mechanism on which the driver can count.

Ninety-nine times out of a hundred, when a car slows suddenly the driver is retained in his seat by applying pressure with his left foot against the floor or the car or the dead pedal. You could test this yourself by driving across a parking lot with your left leg tucked under your bottom, hitting the brake pedals with your right foot hard enough to engage ABS, and then observing what happens. Make sure there’s nothing around for you to hit, of course, because chances are you’re going to slam against the steering wheel pretty hard and lose some or all of the control you have of the car. You’re certainly going to lose any ability you have to modulate brake pressure during the episode; the weight of your body will be transmitted through the brake pedal and you won’t be able to stop braking until you’ve come to a halt.

The above scenario is why your high-school driving instructor wouldn’t let you left-foot brake. It’s not a reasonable way to operate a vehicle on the street at any kind of speed. If you’re in a car as a passenger and you see the driver using the left foot to slow said car, you should speak up. It’s dangerous and not advised, period.

What about when you’re crawling in traffic, however? In situations like that, I left-foot-brake all the time. I wouldn’t say there’s anything wrong with it. At five miles per hour, it’s pretty tough to get yourself killed with even a full-pressure random brake application. I also have no reason to believe it’s particularly hard on brake linings or torque converters. The forces involved are a fraction of what the car can generate. I just swapped out the front brake pads on my Town Car for the first time — at 93,500 miles. I haven’t changed the rear pads, because they don’t need it yet. If driving said Town Car in traffic with both feet is hard on the brakes, I have to wonder how long they last if you don’t drive the car with both feet. 200k? Forever?

Professional drivers — as in professional livery drivers, not LMP2 pilots — use both feet in traffic to smooth the passenger experience. If the brake is applied as the accelerator is released, and vice versa, it’s possible to creep through traffic without jouncing the VIPs. As some of the readers noted, however, most modern cars are considerably more sophisticated than Panthers. They’re engineered for legal considerations as well as mechanical ones, and one of those considerations is that the brake must always stop the car immediately even if the accelerator is being pressed. Therefore, to avoid being the subject of a “60 Minutes”-style hatchet job, nearly every car you can buy today closes the throttle the minute it thinks you’re operating the brake. As I noted in my Focus test, double-clutch automated manuals are also confused by operating both pedals at the same time, even briefly, and they’ll misbehave as a result.

So, let’s review. Driving down the freeway? Put your left foot on the floor and leave it out of the proceedings. Stuck in traffic? If you have a torque-converter car without the latest in paranoid electronics, feel free to use both feet. If you have a DCT or, say, a modern Audi sedan, your experience might vary.

That covers all possible experiences on the street. What about on the racetrack? Here we have a different set of rules. On a racetrack, we have a five-point harness holding us in the car. We don’t need the left foot to support the body during hard braking. If we don’t have a five-point harness, a CG-Lock also works very well. It holds the lap belt in a fixed position and retains the driver’s body in the seat during deceleration. Every Stock-class autocrosser worth his salt uses one. I brought one to the CTS-V Challenge only to find that Bob Lutz’s car, which he shared with me, already had a heavier-duty variant of the CG-Lock installed.

Once properly belted and restrained, we are free to use the left foot to brake. In stick-shift cars, we can only do so when we aren’t downshifting for the turn, and that doesn’t happen very often. In an automatic-transmission car or an automated manual, however, we can left-foot brake for each and every turn, as I did in my recent on-track test of the Camry SE.

Noted IndyCar driver Alex Lloyd wrote a column about why you should brake with your left foot at all times. He points out that you can lose up to one second every time you move your foot from the accelerator to the brake and vice versa. That’s totally legit, and it’s the biggest reason to LFB on a racetrack. (The second-biggest reason is the additional ability you get to adjust your car in the midcorner if you’re free to use both pedals in sharp succession.) It’s safe to say that there are very few professional drivers (in the non-livery sense) using their right feet to brake unless they’re concurrently using their left foot to operate the clutch.

His claims that you should use the left foot to brake on the street so you can go faster on said street, however, should probably be disregarded. If you’re braking hard enough to really make time on a fast back road, you need your left foot to brace your body. I forgive Mr. Lloyd for forgetting to mention this, since my guess is that he’s been too busy racing IndyCars and doing exciting stuff like that to put in a couple of thousand laps in the right seat of student-driven cars at open-lapping events. Unfortunately for me, I have not been too busy to do exactly that, so I’ve seen the negative outcomes that happen when people try to use their left feet to brake the car while wearing a traditional three-point belt. I do agree that you can theoretically brush your left foot on the brake in fast street corners to adjust the car, but what happens if you’re in the middle of doing that and a deer runs in front of you? You’re going to max-pressure the brake pedal with that same left foot, and then, as Al Pacino tells DeNiro in Heat, “brother, you are going down.”

It’s best to think of left-foot braking as the equivalent of biting your girlfriend. You can do it softly when you’re just messing around, and you can go for it when you’re full-throttle, but in everyday situations it might be unwelcome. No, wait, that’s a terrible analogy. Let’s just say this: that when it comes to left-foot braking, as with everything else, the answers aren’t as straightforward as they might initially seem.

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Ask The Best And Brightest: When Are Two Pedals Better Than Three? Fri, 06 Apr 2012 13:00:17 +0000

A scheduling conflict led me to be booked into a 2013 Mazda CX-5 SkyACTIV. With Jack and Brendan having already driven the car, I’ll spare you all yet another review discussing Mazda’s latest crossover. But a week in the CX-5 raised an interesting question; when are automatics better than a stick shift, even if it’s a vehicle that (arguably) has some appeal as a driver’s car?

The Mazda3 SkyACTIV, as well as the CX-5, both use Mazda’s newest SkyACTIV powertrain. As my review of the Mazda3 revealed, the SkyACTIV powertrain is better suited to the 6-speed automatic, even though the manual is a great gearbox. Driving the CX-5 confirmed this. The CX-5 seems to want to upshift to the highest gear ASAP, but when commuting, I don’t find it so bothersome. The transmission kicks down when needed, shifts are beautifully smooth, and the manual model enables nearly unfettered use of all six forward gears.

The SkyACTIV isn’t the only instance of a two-pedal gearbox being the one to get. The E60 M5 was famously set up to work best with the SMG gearbox. U.S. gearheads complained until BMW relented and offered a six-speed manual. It turned out that the stick shift was a poor choice for the car, no matter how much enthusiast cred it added. Most of the time, I’ll take a stick shift, even though I engage in a lot of stop-and-go driving. But my memory doesn’t extend far enough to remember the muscle car era, when an automatic was often preferred. Best and brightest, fill in the gaps in my knowledge. When is an automatic the gearbox of choice? Or am I just plain wrong?

InteriorTac 2013 Mazda CX-5. Photo courtesy Adam Wood. CX-5_3 CX-5_4 CX-5_5 Zemanta Related Posts Thumbnail InteriorTac CX-5_1 CX-5_2 CX-5_3 CX-5_4 CX-5_5 CX-5_6 CX-5_7 CX-5_8 CX-5_LOGO CX-5_SKYACTIV Interior1 Interior2 Mazda CX-5 Automatic. Photo courtesy Adam Wood. Interior4 Interior5 Interior6 Interior7 Interior8 Interior9 Interior10 InteriorNav ]]> 123
Piston Slap: Justy-fied Freestylin’ over CVTs, Part II Wed, 19 Oct 2011 19:06:23 +0000  


Brian writes:

Not sure if this would be appropriate “piston slap” fodder or not, but here goes:
Our blossoming family recently expanded to five. My wife and I, and a three year old, a 20 month old and now a 2 month old fill up the house. We occasionally travel with our 75 lb dog. Knowing the Volvo Turbobrick would not handle the cargo/dog/people, and the PT Cruiser remains the most reliable vehicle ever built (even if the timing belt changes are a big pain) we decided to sell the Volvo for something more appropriate, if a lot slower and FWD.

Enter the Freestyle. We routinely get 28 mpg on trips, parts are cheap, we have lots of cubbies for kid’s junk and the car seats fit easily. I purchased a high mileage (150k) example that was a one owner (ish) with all receipts. It was a fleet car for some guy who then bought it when his company was done with it. It had the CVT replaced at 118k miles with a remanufactured transmission from Ford, installed at a dealer.

A few weeks ago the CVT died on us. At 153k miles. There was just over 1,000 miles left on the warranty. We all got home safe and sound, and the transmission was replaced. Again. With a remanufactured unit. Again. It’s apparently the only thing available. No new ones exist and nobody rebuilds them. I have a connection with the transmission rebuild world. I’ve called transmission parts suppliers and they don’t even sell a manual for it.

I’m not what you’d call ‘shy’. I do all my own work on my cars with the exception of this, flashing the ECU for a TSB on the aforementioned PT Cruiser, putting tires on wheels and replacing windshields. I’ve done a fair amount, but I’ve never owned anything this expensive. I fully expect this remanufactured transmission to die in roughly the same amount of time. My theory is that while the original certainly seemed to fare decently (118K on a conventional transmission is not terrible for a heavier people mover), the reman probably was rebuilt by the same folks who do the $34.99 starters for small block chevies that seem to last just a day over the one year warranty that you find in the local pep-advanced-zone’s. The choices are basically as follows:

Take a big depreciation hit and attempt to sell it (we bought it in March) and buy a Taurus X with the conventional automatic and the better 3.5L engine. We cannot afford this now, but I have a few years to see that mileage on the reman CVT.

Replace the CVT in the Freestyle with the 6F in the Taurus X. I know this isn’t easy. The engine should bolt right up, and the mounts should be pretty close (I have a welder and a hammer) but the ECU is the tricky part. This is not a slam dunk.

Replace the CVT in the Freestyle with the Aisian in the 500. This is only slightly more of a slam dunk, because it’s probably the same ECU. I just need to find out how to flash it.

Learn to rebuild the CVT myself and build a great one and keep it onhand as a spare. My neighbor has a lathe and Bridgeport in his basement. I am a degreed engineer. It would take a while, but it could work.

Sajeev answers:

Oh yeah, this is totally a Piston Slap worthy article. Not like we haven’t done this before, ya know. And while I am (a little) surprised that a Ford Reman transmission does this poorly, who knows who actually did the rebuild! It’s an orphan design, which is never good. The ideal transmission for the long haul of ownership is something with tons of support, and GM transmissions have usually done the best for decades, for this reason. And if you can’t procure a 100% new, never rebuilt CVT assembly, I agree with you.

Having done transmission swaps before (and truly hating myself during that time) and knowing a bit about Ford electronics, here’s my recommendation: do that 6-speed swap. Get a Hollander Interchange manual to find out which Fords used the same vintage 6-speed as the same year of your Freestyle. If you can easily snag that gearbox from the same vintage Five Hundred, you are set. But who knows, maybe there’s a cheap wrecked Fusion nearby that has the same part for much less! It all depends on the market and availability.

From there you will need to see what’s different in the mounting and wiring of the transaxle on the subframe. Maybe you need a different mount, maybe not. Perhaps there’s an extra wiring harness, or a completely different one! Maybe a new shifter in the console too. Hopefully not, and a factory shop manual with wiring diagrams will help.

Once you clear that hurdle, the final part is easy. The ECU’s are pretty simple, as Ford hasn’t made a significant change in them during this era. Odds are you can take any one of them and re-flash the correct transmission logic with a brilliant person and an SCT tuner in his pocket. Which will set you back up to $500, I suspect. That’s your fallback, because I suspect getting a matching computer from a donor Ford Five Hundred will make it all work great…but if not, the SCT-tune is the way to go.

It will be a ton of work, both in research and sweat equity. But I suspect a smart dude like yourself can get this done for under $1500, if you get lucky with the cost and quantity of parts needed for the swap.

Best of luck.

Send your queries to . Spare no details and ask for a speedy resolution if you’re in a hurry.

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Piston Slap: Nissan Matic J Worth The Trouble? Mon, 04 Jan 2010 15:09:46 +0000 Matic-depressive?

TTAC commentator Kericf writes:

First, an update: I submitted a question on my Rodeo ABS and brakes before. It was just a bad sensor (probably from driving in high water). And I chose not to replace the brake lines yet after inspecting them.

Now, my new question comes way of a transmission fluid change on my wife’s 2005 Pathfinder. As usual the manual calls for only using official Nissan Matic J at almost $13 per quart. The local auto parts store sells Castrol Tranny fluid that says on the label it is a replacement for Matic J. I do not have any warranty left so I’m not so much worried about fighting over what was used, I just don’t want to have to replace the tranny because the fluid wasn’t the right spec? Am I worrying too much about it? Should I just dive right in and go?

I would also like to get some suggestions by the B&B on the best way to flush more fluid out than the standard drain 5qt out of the pan method. Is there a way to really get it all out on your own? I saw the product review on the oil extractor and was contemplating trying one out for the tranny fluid as it seems a lot easier and cleaner.

Sajeev replies:

Congrats on the easy fix on the Rodeo! On the Pathfinder, use any fluid that meets the manufacturer’s specifications, and I suspect the Magnuson Moss Warranty Act agrees with me too. So yes, dive right in and go.

I seriously doubt the engine oil extractor (per TTAC review) has the balls to vacuum through the guts of a torque convertor; only the pressurized flushing systems can pull that off. If you’re lucky, you can pull the pan (and whatever trim covers the torque converter) and spin the converter 360 degrees and hope that Nissan gave you a drain plug. If not, I suspect the flushing machine is your best bet.

As previously mentioned on Piston Slap, your best bet is to do both a filter change and a flush of all the old fluid. Try to find a shop that can do both, unless your Pathfinder has well over 100,000 miles with original fluid, you might want to reconsider flushing the varnished fluid (filled with clutch material) with new slippery stuff, as that could wear out the transmission much faster. Fluid changes on old automatic transmissions are a tough personal choice, so think before you act.

Off to you, Best and Brightest.

(Send your queries to

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Piston Slap: Another Honda, Another Busted Autobox Mon, 23 Nov 2009 17:02:35 +0000 Oy!

TTAC Commentator jpcavanaugh writes:

A friend has a 2005 Acura TL which he bought as a certified used car at about 2 yrs and 40K miles on it. He bought the extended warranty to 100K. I recall thinking “its an Acura, why waste the money on an extended warranty?” It turns out he was right: at about 60K, he noticed an occasional judder during transmission shifts. The dealer informs him that the transmission is shot, and that it will be replaced under his extended warranty. After a couple of days, he gets the car back (he did enjoy the RL he got as a loaner) and the car is fine. Until now.

He noticed some fluid on the floor of his garage this morning. His regular mechanic says that it appears to be coming from the overflow tube. Back to Acura dealer, who says they have been authorized to replace the transmission again.

The car has about 68K miles now. My friend is in his late 60s and is starting to get concerned. He has been planning to keep this car for a long time, and has no other complaints with it. He really doesn’t want to get another car, but is becoming leery that at some point, another transmission will fail and he will have to write a 4 figure check.

I have heard that Acuras of the early 2000s were cursed with transmission problems (like the Odysseys of the era) but had understood that the problem was largely solved by 2004. But evidently not with this car. My flippant answer was that he could swap for a late model Town Car for no net cost, but I don’t think he wants to do this. He has had a series of stick shift Acuras and enjoyed them (the last was a RSX Type S), but he bought this to have a grown-up car that is easier on his back. So, what am I to tell him? My knee jerk reaction is to dump the car. But if there is a known fix that will take care of his problems for the next 120K miles, then maybe keeping it is a good idea. I’m sure that you and the B&B will steer me in the right direction.

Sajeev replies:

How ironic: a friend’s 2000 Honda Accord recently needed my assistance out of harm’s way after the transaxle grenaded…for the second time. As you mentioned, if everyone put long-term cost of ownership “uber alles,” we’d drive a late-model Town Cars or Crown Vics. And that’ll make the whole country look like Manhattan Island. But nobody wants that.

I’ve been in your friend’s shoes: rebuilt transmissions can need minor adjustments (new O-ring at the speedometer sensor, re-torquing some external bits, etc) a month later to fix the problems that crept up outta nowhere. But my tweaks were on a hi-po Ford AOD (not exactly a complicated unit) rebuilt locally at a franchise transmission shop, not a dealership using Honda transaxles from a shipping crate. Big difference: so your “knee-jerk” reaction mirrors mine.

I’d dump it too. Late model transmissions are black holes for your wallet, especially if it requires multiple dealership visits. The leak from the overflow tube says less about Honda’s glass-jaw transaxles and more about the people installing them. If the Acura forums don’t have the details to explain your screwy scenario, I’d sell (or lemon law) this car. If your friend really loves the Acura brand, get a 2008 TL and hope for the best.

But no newer than a 2008. Because no matter how robust the 2009 TL’s powertrain might be, friends don’t let friends drive ugly cars.

(Send your queries to

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Chevrolet Cruze’s “Flawless Launch” Delayed by Transmission Problems Thu, 12 Nov 2009 14:17:15 +0000 Cruze control. Or not.

When GM CEO Fritz Henderson promised Congress he would run the nationalized automaker with complete transparency, we knew he was full of shit. How could anyone expect New GM to do anything but lie, misdirect, prevaricate and obfuscate when the same Bozos that ran it into the ground were still large and in charge? Which GM dealers are canned? Which GM dealers have been resurrected? Why? Who is the GM executive (other than Fritz) who earns more than $500,000 per year—that the company refuses to name? What are the internal targets that GM says it’s meeting? Why did the company overestimate sales of some of its key models in its November press release? Why did Fritz and CFO Ray Young promise a 2010 GM IPO without the Chairman’s approval? And so on. To that list, add this from the AP: “But GM postponed the Cruze’s April build date about three months, said Mark Reuss, GM’s vice president of global vehicle engineering. The company, he said, wasn’t happy with the Cruze’s performance, especially with the six-automatic transmission. ‘No one was thrilled with where it shifted, how it shifted.’” Well that’s the first I’ve heard of that. And while it’s nice that GM is putting our money where it’s mouth is in its desire to ensure the Cruze’s “flawless launch,” what the hell happened? And why wasn’t anyone fired for it? Oh right, GM.

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