Does Hypermiling Damge Your Vehicle???

[MaxxMPG]

Originally Posted by jkp1187

Thanks for the advice.

You're sure about there being no issues going from "N" to "D"? I went through two transmission in this awful old Chevy Beretta I had, so I'm a bit paranoid about automatic transmissions -- they always seem to me to be just so much witchcraft. The Impala has been strong so far, but I wouldn't want it to die prematurely because I was trying to eke a few more MPG's out of it.

No issues shifting between N and D. The Impala is not flat-towable, so keep the engine running. Remember that shifting to N doesn't provide vastly better fuel economy, but rather just helps to keep the speed of the car up when coasting. The only time I use N is when crawling from light to light in a congested area, where a quick goose of the accelerator will get the car moving at about 15mph and then bumping to N helps to maintain that momentum to crawl to the next light.

For GM automatics, you don't need to rev match, just move the lever from N to D with no throttle and then when drive engages, you're good to go.

The old Beretta, if it was a 3 speed, probably developed a few known quirks as the miles accumulated. The most common was a sticking torque converter clutch. When you stop the car, it stalls. My dad and my brother both had different cars with this issue. The solution, raise the hood, unplug the TCC connector, close the hood, and drive the car trouble-free for another 100k miles. There was never any serious change in FE, either. That trick doesn't work for the 4 speeds, but it was a great way to keep the 3 speeds going long after they should have been repaired. If your Beretta was a late 80s (early build) car, it could have also had a worn accumulator bore (causes slippage in 2nd gear), but that was "fixed" a long time ago in the endless revisions of the old transaxles. Even on those old TH125C transaxles, N to D and D to N was harmless. The easiest way to kill them was to shift from R to D or D to R with the car moving above 3 or 4mph. Enough people drive that way, and it caused GM some warranty fits back in the '80s. When GM reprogrammed their "Transaxle Designer for Windows" program with the added line of "our owners don't bother stopping before shifting, so beef up the rear sun shell so it stops cracking", and "They only change their transmission fluid when they see Halley's Comet", the perceived reliability improved greatly.

The only automatic transmission that actually uses witchcraft (and behaves as though it was possessed) was the "Roto Hydramatic" transmission of 50 years ago. It, along with the later "Super Turbine 300" are credited with putting AAMCO and Lee Myles in business and making millionaires of the shop owners.
The Roto-Hydramatic was installed only in 1961-1964 full size Oldsmobiles and Pontiac Catalina/Ventura/GrandPrix models in those four model years. It had a tiny fluid coupling (that worked similar to a torque converter) built *inside* the transmission, where you had to disassemble the transmission to remove/repair/replace it. And also, stalling the converter caused severe damage in a short time, since the location - deep within the transmission - meant the extreme heat couldn't be radiated away properly. And if that's not bad enough, the car shifted by draining and refilling the torque converter. For first gear, the converter filled and transmitted power through gear reduction to the rear wheels. For second gear, a separate friction clutch applied and the fluid was dumped from the converter. For third gear, the converter refilled, providing two separate paths for engine torque, causing the two power paths (the friction clutch and the fluid coupling) to spin at the same speed, resulting in 1:1 direct drive. It is the only transmission I know of that shifts into 3rd gear by applying 1st and 2nd at the same time.
If you think it sounds like a bad idea so far, it gets worse. First gear was 2.93:1 and second gear was 1.56:1, which is a fairly steep gear change. But as second gear applied via a friction clutch, there was no longer a fluid coupling to smooth out the shift. The car would lurch on the upshift and lug (and sometimes stall) the engine - a feeling similar to shifting a MT car from 1st to 3rd and bringing the clutch pedal up too fast. And if the throttle rod adjustment wasn't perfect (and that's where more witchcraft was needed), the car would shift very early (killing the engine on the 1-2 shift) or very late (overheating the transmission), and might not even shift up to top gear.
The transmission became known as the "slim jim" back in those days, as it was much narrower than the cast iron Super-Hydramatic (ie; "Controlled Coupling Hydramatic") it replaced in those Olds/Pontiacs. Any mechanic who knows "old cars" will tell you to "stay the hell away from it".

In comparison to those early days of automatic transmission design (you can look up other 1950s-1960s disasters such as Flight-Pitch, Turbo-Glide, Ultramatic, and Dual-Path), modern automatics are very friendly and efficient. And with recommended maintenance and sane driving, they last a long time. Most "transmission problems" today are usually not much more than bad sensors or solenoids, or at worst, worn parts in the valve body. And the repair costs, adjusted for inflation, are a fraction of what they were half a century ago when people accepted the idea that their transmission wouldn't last more than a couple of years.

[jimepting]

Well, here we go again. It seems to me that there is a strong desire by many to believe that operating manual transmissions in a manner for which they were never designed will result in no addition wear. That conclusion just doesn’t seem justified by analysis of design methods, or by analysis of the actual construction and function of manual transmissions.

It seems very reasonable to conclude that all things mechanical are designed with an “acceptable” tolerance for wear. In past years, many have complained about “premature” failures of components on American made cars, with some justification. The components of several imported brands have better reputations, and obviously have greater design safety factors for mileage and cycles. So by experience, we can say that the design engineer can and most likely does control the design “life” of components. To increase the cycles on a mechanical component, such as the transmission, is to more quickly exhaust the design cycles of some parts within, particularly the synchronizers and the dog clutches in the case of pulse and glide hypermiling methods.

As far as the actual functioning of the transmission is concerned, it is the synchronizers and dog clutches which take the lion’s share of wear when pulse and glide methods are used. If one reads and studies the references, then it is apparent that there is high relative motion between the two halves of the synchronizer assembly, the cone and reverse cone, when the car is coasting in neutral at speed. If the engine is on, then there is the opportunity to double clutch and do some rev matching, If the engine if off, then no rev matching can take place when engaging a gear, and the wear is accelerated.

Is the practice going to “kill” your transmission? It is safe to say that wear is accelerated, but there is no conclusion possible as to how much wear is too much. And, if the manufactures could be coaxed to speak, they would likely disavow any warranty protection for such a practice (assuming that they could prove it). According it many accounts here, the largely imported transmissions are pretty tolerant of excess shifting, though I think I recall a few failures. It is likely that many practitioners will not experience trouble in the period that they own the car. I don’t own an MT car, but if I did, I would risk “some” Nice-Off coasting when the coasting length was significant, but I wouldn’t engage in a lot of Nice-Off pulse and glide coupled with bump starting, which is the worst case wear situation.

References:
http://auto.howstuffworks.com/transmission3.htm
This is an excellent ref, with lots of good graphics, some animated.

http://en.wikipedia.org/wiki/Manual_..._configuration
This an extensive write-up with some interesting sections on the configuration differences between fore/aft rear drive manual transmissions and transverse transmissions, though the differences do not change the method of gear engagement.

[jkp1187]

Originally Posted by MaxxMPG

The old Beretta, if it was a 3 speed, probably developed a few known quirks as the miles accumulated. The most common was a sticking torque converter clutch. When you stop the car, it stalls. My dad and my brother both had different cars with this issue. The solution, raise the hood, unplug the TCC connector, close the hood, and drive the car trouble-free for another 100k miles.

Actually, don't recall this ever being a problem. I had a '95 4-cyl 3-speed base Beretta, bought it used in '98 from my neighbor, who'd already put ~ 60,000 miles on it. And man, they must've been hard miles. Things just went wrong with that thing left and right. The turn signal lever even snapped in half. No, the first transmission just broke when I was accelerating up a hill one day, no real warning, absolutely no power in any gear after that. I had some warning for the second one, noticing a lot of hesitation in low gear from a standing start, then one day, after driving ~ 2 hours on the highway, I parked at a mini-mart, came out, and found that I no longer had a reverse gear.

Thanks again for the information. I'll consider using "N" next time I'm in stop-and-go driving. Did you used to work on transmissions?

As an aside, I don't think I'd ever bother with NICE-off gliding just because I don't want to horse around a car without power steering.

[MaxxMPG]

Originally Posted by jkp1187

Actually, don't recall this ever being a problem. I had a '95 4-cyl 3-speed base Beretta, bought it used in '98 from my neighbor, who'd already put ~ 60,000 miles on it. And man, they must've been hard miles. Things just went wrong with that thing left and right. The turn signal lever even snapped in half. No, the first transmission just broke when I was accelerating up a hill one day, no real warning, absolutely no power in any gear after that. I had some warning for the second one, noticing a lot of hesitation in low gear from a standing start, then one day, after driving ~ 2 hours on the highway, I parked at a mini-mart, came out, and found that I no longer had a reverse gear.

Thanks again for the information. I'll consider using "N" next time I'm in stop-and-go driving. Did you used to work on transmissions?

As an aside, I don't think I'd ever bother with NICE-off gliding just because I don't want to horse around a car without power steering.

The Beretta symptoms point to a problem with the oil pump in both cases. It's a vane-type pump that doesn't have much room for abuse, so overfilling or a clogged filter can do damage (scoring of the pump body or fractures in the vanes) that will cause the hesitation and eventual failure you mention. Reverse gear usually requires the largest volume of fluid and highest pump pressure to engage, so a delayed or sloppy engagement of reverse is the first symptom of low fluid, foaming (from overfilling) or a problem with the pump or pressure valve.

Sadly, many transmission shops today sell rebuilt transaxles without properly diagnosing a problem. It is more profitable (more money for the same number of man-hours) to remove/replace a transaxle that was hastily rebuilt by an outside supplier than it does to plug a pressure gage into the different taps and nail the problem down as a bad pump or valve body or leaky clutch seal. The slapped-together reman'd units carry a 12/12 warranty because that's about how long they are expected to last. There are lots of Chrysler transaxle horror stories that are caused by shoddy rebuilds and not by an actual problem with the design itself. The other manufacturers have similar horror stories, too, but Chrysler's unique design requires a re-flash of the transmission controller before running the car for the first time. If that is not done, the transmission is damaged when the car is first driven, and will fail within a year or so.

I have done some Saturday driveway work on transmissions, but never chose it as a career path. But I have plenty of auto techs in my circle of family and friends, and some great research skills I use to look up the details, the manuals, the trade publications, and other sources of hidden gems. Just for fun and curiosity, I often research the "old" powertrain technologies (as is evidenced by the Roto-10 description above) because the "powertrain engineer" inside me wants to understand what has worked over the years and what hasn't, and why. A ride in a '62 Olds years ago led me to look up the reason why the car had such a horrible thump on acceleration and why the mechanics always said, "they all do that". It is amazing to read the engineering details of a defunct engine or driveline and then go over to another site to read about what problems people had with what "on paper" looked like an engineering marvel.

Since I'm the "go-to" guy that my family/friends/coworkers come to when researching a new or used car, I keep a mental database of "safe" and "risky" buys in both new and used vehicles. The detailed and accurate information here at CleanMPG is a great additional resource for these reliability/durability/efficiency statistics, along with the compiled wealth of safe and risky FE tweaks for the diverse assortment of cars and trucks we all drive.

[jkp1187]

MaxxMPG,

Thanks for the suggestions. I tried a little NICE-on gliding on the way home from work today. For the first time ever, my MPG average actually went up on that phase of the drive home between the interstate and my house (which is a somewhat hilly drive through a residential area involving lots of red lights and stop signs.)

And I did see on the tachy what you were talking about regarding dfco. It was wild to see the tachy blip upward just a hair after I pushed the brake pedal. Never noticed that before.

[ascribe2thelord]

Hypermiling is defined as getting higher mileage than the EPA. Some of the techniques used to do that can damage your vehicle.

Safe techniques:

1. slowing down in advance of red lights so that when they turn green you can coast through.
2. driving slower
3. driving with load (this is not the same as lugging the engine)
4. higher tire pressure (up to a point, because if bumps jar the vehicle frame too much it might cause damage)
5. taking the first parking space available instead of lingering around to find a close one
6. accelerating slowly (and braking slowly so you don't have to speed up too much later)
7. stopping the engine at red lights

Techniques that CAN damage your vehicle, or are generally dangerous:

1. going from neutral to drive in a car not designed to do so, without knowing how your vehicle handles it best (this may take a lot of time to figure out and in fact you may not be able to do it at all)
2. tailgating an 18-wheeler (thrown out of the hypermiling repertoire years ago for being too dangerous as well as not being effective enough because trucks usually drive much faster than hypermilers, plus you have to catch up to the truck to do this, thus wasting gas) ++ add on note ++ you may try drafting buses instead, but keep your distance
3. taking curves too fast for either your vehicle or your own abilities
4. turning your engine off, if your vehicle isn't flat towable and you don't know how to steer/brake with the engine off