When we talk about a four-speed auto or a five-speed manual, we’re using shorthand. We’re talking about the number of forward gears these transmissions have. Really, though, they have five and six gears respectively, if we include the reverse gear. Indeed, the vast majority of automotive transmissions ever built have a reverse gear.For Mercedes-Benz, though, that wasn’t enough. They built a significant number of transmissions with two!
Yes, the Mercedes-Benz 5G-Tronic transmission, also known as the 722.6, was built with two reverse gears from its debut in 1990. Revered as a stout and capable automatic transmission with five forward speeds. Its successor, the 7G-Tronic (722.9) debuted in 2003, and also featured two reverse ratios in addition to seven forward ratios.
You could be forgiven for thinking Mercedes was attempting to build some kind of crazy autocross transmission for faster driving in reverse, but that couldn’t be further from the truth. In fact, these were commodity transmissions featured in a wide variety of the company’s models, from humble four-cylinder compacts to turbocharged V12s.
The purpose of the extra reverse ratio is explained by a single detail in the cabin. Many Mercedes models of the late 1990s featured a switch by the shifter labelled “W/S.” This is the winter/standard mode selection switch. As explained in the manual, it’s for switching between driving in slippery, snowy conditions (winter mode, W), or regular dry conditions (standard mode, S).
In winter mode, the transmission will typically start in second gear when setting off, both in forward and reverse. This reduces the likelihood of wheelspin and bogging the car in snow. The transmission also shifts earlier in this mode. In contrast, in summer mode, the vehicle will start off in first gear, and the engine will be allowed to rev out more before the transmission shifts up. In some later applications, the two transmission modes were designated as “comfort” and “sport” instead.
Mercedes sold these transmissions to a number of other automakers. You can find the 5G Tronic (722.6) in everything from certain models of the JK Jeep Wrangler to the Chrysler 300 and the Dodge Charger. This cross-pollination continued to occur long after the dissolution of the Daimler-Chrysler merger, and the transmissions also showed up at other automakers too. Another notable user is the Jaguar XK from 1998 to 2002. Ultimately, other automaker were happy to use the 722.6 because it could handle the torque output of high-performance engines, and it had favorable driving characteristics. The 5G Tronic actually remained in use until 2020, with its last application being the Dodge Charger Pursuit.
Perhaps the most interesting user of the 722.6 was the Porsche 911 Carrera and Turbo from 2001 to 2010, in automatic models. These models used a special transaxle version of the 722.6 that had a hole in the bellhousing beneath the input shaft. This allowed the driveshaft to pass underneath for driving the rear wheels in the 911’s rear-engined configuration.
It took me an hour of specific research, but I was able to find proof that the Porsche 911’s version of the 722.6 got two reverse gears, just like all the others. Feast your eyes on this excerpt from the 2008 Porsche 911 owner’s manual, referencing the Tiptronic S transmission:
It’s unclear to me under what circumstances the Porsche version of the transmission might use either reverse gear. It doesn’t have a “winter/summer” switch as per the Mercedes models. However, it does run the 722.6 in a more aggressive shift mode when the vehicle’s Sport mode is engaged. It may be that outside of Sport, it enables the use of the lower-ratio second reverse gear which would be better for slippery conditions.
The later 7G Tronic (722.9) transmission didn’t see quite the same wide level of usage as its predecessor. Indeed, the 5G Tronic actually remained in use in several of Mercedes’ V12 models due to its ability to handle immense amounts of torque. The 7G Tronic would eventually transplant the 5G Tronic, though, across most Mercedes models. It would also show up in the Infiniti Q50 for a few years, and the SsangYong Rexton as well.
When the 7G Tronic was replaced with the 9G Tronic, Mercedes no longer saw fit to include two reverse ratios. It’s likely the engineers decided it was not really necessary, given no other automaker was pursuing the same solution to snow driving. Plus, by the time the 9G Tronic was released in 2013, computer drivetrain controls were mature. Traction control could instead solve the problem rather than simply gearing down the engine.
While having two reverse gears is a neat feature, it’s also a pretty obscure one. Moreso than that, it seems likely that many owners were never even aware they had multiple reverse gears. Unless you paid close attention when driving your vehicle in the snow and flicking between modes, you’d probably never pick up the difference in reverse gear ratios.
These days, it seems unlikely any automaker would go with such a mechanically complex design, when modern electronic engine and drivetrain controls can do a better job in traction-limited situations. Regardless, we have Mercedes to thank for producing a stout and highly unique transmission that ended up in a ton of excellent cars. If you’re driving around in a vehicle with the legendary 722.6 or 722.9, see if you can identify the two reverse gear ratios on your vehicle. Report back to us whether you think this feature is fantastic, or folly. Happy driving!
Image credits: Mercedes-Benz, Porsche, Favcars.com, eBay
Fascinating stuff. Of course the Aussie 60s Lightburn Zeta had 4 gears, which could run backwards
A lot of tractors have multiple reverse gears which is really nice for backing up equipment slowly or having the option to go a bit faster.
I sometimes used low range on my previous manual truck for backing trailers in tight spaces without having to slip the clutch so much. Doesn’t work good on pavement though.
I have an old Jeep CJ with the manual hubs and I do the same thing, put it in low range but leave the hubs unlocked so it is essentially 2wd low. Makes it a lot nicer moving around in tight spaces.
911 wasn’t only Porsche model to “borrow” the Mercedes-Benz gearbox.
928 had a gearbox with Mercedes-Benz internal components inside the Porsche-designed housing and transaxle. An unusual move given the fact that Audi had a suitable automatic gearbox from 100/200/5000 (C2), used in 924.
That was the 722.3 transmission, a 4spd non lockup. I know this because my W126 also has a 722.3 and all the info for re-sealing the case I got from the 928 forums.
The 722.6 was pretty bombproof, but I never knew about the two reverse gears. I always wondered what the W/S switch on the dealership’s W163 was all about.
It also saw use in V6 Sprinters until the rollout of the 907/910 chassis vans in 2019. 4-pot vans had the 722.9 7-speed and was a bit of a PITA to service. If we weren’t replacing 642 oil coolers that were puking all over the valley of the block, we were throwing conductor plates at those 7-speeds.
I will say, having gear ratios printed in the owners manual was helpful with a stick shift Cavalier with no tach – do a bit of math one evening, and I had the rough max speed per gear,so less worry about overrevving
My Subaru just straight up lists the max speeds in the owners manual, no math required. I wonder why Chevy didn’t do the same.
The accountants at GM, who also happen to be the technical writers, decided that printing the max speeds for each gear would have taken up far too much precious, and costly, ink in the manual.
I learned to drive manual on a car with no tach. My old man just told me to listen to the engine. Obviously it was not a performance car and I wasn’t revving it way up.
This wasn’t a performance car either, but it sounded a little thrashy no matter what. I just found it a reasonably useful application of the data.
This is interesting, but a remarkably dumb engineering decision by Mercedes(surprise surprise).
I have never once taken off in 2nd as a means of preventing wheelspin. It is so easy to just not press the accelerator hard enough to spin the wheels. I have extra never done that in reverse. The very significant extra cost and weight of a 2nd reverse gear is so not worth the absolutely miniscule benefit that 92% of drivers won’t use even once.
Using the weight and financial budget spent on the 2nd reverse had to add another forwards gear would have undoubtedly made for a better all around car.
I’ve used higher gears to avoid wheelspin in really bad conditions, eg a 2wd hatchback in deep snow. It always worked really well for me.
I love love love cutaways, especially detailed cutaways. Any chance we can flip a switch to make tapping on images open in a temporary popover?
My 2009 CLK350 has the 7 speed – and yes, the switch is C/S.
I was going to say that my car has only seen snow twice in the years I purchased it CPO – and was purchased in Beverly Hills….
….but it’s really about what mode the transmission the car is switched to, isn’t it?
I keep it in “Sport” 99% of the time. Set it in S and forget it. Unless a valet or mechanic switches it to “Comfort” for some unknown reason – like they do with the headlamps from “Auto” to “Off”…
yeah! exactly.
Speaking for me, but I still strongly dislike “auto” headlamp switches. I want to see the car’s headlights off when I leave it as reassurance, and the only way I way I get that is by turning them off myself.
Conversely, I always turn on my headlights when I’m driving, so I need to force them on rather than rely on “auto” (….even though the two vehicles I’ve owned don’t actually have that option).
Here’s an oldie but a goodie:
https://www.cartalk.com/radio/puzzler/speedy-saab
Where a completely stock 1960s Saab three-cylinder beat a contemporary American muscle car in a drag race.
Now I’m wondering… would using the winter all the time mode also save some fuel? Anyone know?
In theory, maybe, if your driving style suits!
From what I’ve heard though, standard mode is usually better; I suspect second gear may be a bit tall for starts and you end up burning excess fuel.
If I had a spare week and a couple of tanks of fuel I’d do a test but my Merc is dead and it’s probably not worth it at $2.00 a liter for gas
As an American $2/liter sounds awfully expensive. Not sure how the AU dollar converts but I’m paying about $3/gallon right now. A gallon is very close to 4 liters.
Yeah, so US$3 per gallon works out around NZ$1.25 / AU$1.19 per liter. Regular gasoline is around NZ$2.80-2.90 right now, but not sure what the Aussies are paying. I suspect it’s much less.
US$3 per US gallon is a little under 78c per liter – if you were buying in Imperial gallon, that would cost you $3.52. But, the Brits are paying around US$1.85 per liter in London for regular gas.
My head hurts working this stuff out.
No.
I keep mine in Sport and I still get up to 28mpg
(the car is rated at 25mpg highway)
The transmission setting is about how the car moves off the line – not about high-end efficiency.
Yes it will save some fuel in everyday mixed driving as it does pretty much the same thing as eco mode in other vehicles. Both have up shifts that occur sooner than in normal mode, and a remapped throttle to lower throttle response. The difference with this is that 2nd gear start which is an old school way to increase fuel economy in mixed driving.
There was a brief period in the early days of the 3sp AT when it was fairly common for the trans to start in 2nd gear unless you floored it, or selected L and then shifted to D. The most famous one is probably Ford’s “Green Dot” C-4 where you put it in the White Dot position, next of N, for maximum economy in everyday driving with 2nd gear starts. The Green Dot position started in 1st for when towing or maximum acceleration was desired.
Many of the old Allison truck transmissions had a position for 2nd gear starts when running empty or lightly loaded to increase fuel economy.
Try driving a 2wd Toyota minitruck in snow. You’ll start in 2nd every time. 1st gear is about useless unless you are trying to rock it back and forth.
good insight!
Try driving a 911SC in Hollywood traffic.
First is impossible – far too low.
Starting in 2nd is the only way to go.
I drive a 2wd f150 that I once got stuck on totally level ground in my street. I also once got it stuck on level ground in a gravel parking lot on a clear dry day. It is hilariously feeble traction wise. It is also geared very short and is very torquey.
I have never felt a need to take off in 2nd, I just carefully slip the clutch.
Ravigneaux Gear Set. That’s a new one to me. Let’s have an article about planetary gear sets given that they are almost as difficult to comprehend coinsurance.
This seems like a classic German over complication, although not as bad as early 4-matic.
FWIW a lot of machinery has even more reverse gears from either a separate shuttle shift or auxiliary transmission. Some Unimogs have 4 reverse gears between high/low rage and high/low split.
Yeah, I was talking about this in Slack with a fellow Autopian!
Huh. Now I need to see if my 300 has a Winter mode. There’s nothing on the shifter…
I did have another car with two reverse gears: a Dodge Colt with the “twin stick” 4 speed manual. It had two final drive ratios, shiftable on the fly, so you could actually shift gears in reverse, if you had enough room.
There is no excuse for you not having tried this already.
Oh man, the twin stick Mitsubishis look so cool, id love to drive one. Only driven a twin stick heavy truck once but those are dope.
does it have a sport/comfort mode? Love to see what it says in the manual!
I thought W + S stood for Waylon Smithers. Or, depending on how you’re splayed across a sundial, Maggie Simpson.
COTD
My 1999 Jeep Grand Cherokee was changed from a 4-speed auto to a 5-speed auto by a TCM reflash. 2000 to 2004 were five speeds, but exactly the same transmission. For some reason, Chrysler just didn’t use 5th in the 1999 programming.
This is true, the RFE family (or most of them) of transmissions had a different kickdown gear which was only accessed after moving past it at speed, then if you put the throttle down, it would activate it.
Chrysler abandoned this approach with the reflash and all the final versions of the RFE which evolved to be true 5/6 speed autos, which they still make but only (I think) the 68RFE behind only the Cummins motor in new Rams.
The Chrysler RFE transmission was pretty unique for it’s time with how it was designed vs other automatics…ultimately the design was ruined in typical fashion by cheaping out on parts that broke and or warped in the RFE transmissions (i.e. valve bodies cross-leaking, plastic parts that should have been metal, etc..)
the 68RFE is still in OE production, but going away in model year 2025
I sure freaking hope so. The 8HP75-LCV transmission should’ve been a HD Ram staple years ago.
The ZF transmission is really good, however, I’m hearing of failures on these at 100k-150k in Rams/Power Wagons too… not sure why.
The ZF unit should be standard, but the problem is that it’s not engineered for a PTO, neither is the 68RFE, but the Aisin (Toyota HD) transmission is.
So… currently RAM supports three completely transmissions for the same platform. Not to mention that Ford/GM 10-speeds are good… so Ram needs to figure something out that supports PTO that’s in-house or ZF.
The HD Gas all get an 8HP75. If you get a Cummins you get a 68RFE. If you get a HO Cummins you get an Aisin box. For MY25 all diesel rams are going to get the ZF EL58 (an “industrial” 8HP).
https://www.ramtrucks.com/bmo.ram_3500.html#/build/powertrain/48306/CUT202415D23L62A/2TA/APA,PW7,X8,ESB,DFX,DME,Z3S,TCN,WBN,TX,UAA,2GA
Stellantis actually shows what transmission you get on their configurator!
Not with PTO, gas+PTO = Aisin
Crazy. So did it open up a 5th OD fear or did you suddenly find a gear in the gap between 3 and OD?
Some GM 4Ls were almost marketed as 5 speeds once they figured out how to lock up the torque converter
It added a new top gear. RPMs at 70 went from 2400 down to 2000. And this is independent of TC lockup. It was a whole new gear.
I was hoping for some gas mileage increase, but there was no noticeable improvement.
Crazy.. and weird. Maybe the sweet spot for that engine is closer to 2400 under light load.
Thanks for responding!
Looking at the diagram of the transmission, I find it hard to believe that manufacturing that as well as an engine (plus diff, cooling system & fuel system) is cheaper than making an EV. The EV has a shit ton of batteries and an electric motor (plus a cooling system unless you have a leaf) and that’s it. For those of you not familiar with manufacturing, making a dozen gears with really tight tolerance repeatably is pretty hard.
I’m no expert of course but I think it’s a few factors. The main thing is that batteries are still expensive. Costs have come down for sure, but the tech is still constantly in flux, and the raw materials ain’t getting cheaper. And even if the base cost is reasonable, manufacturers want to claw back all that R&D money they spent and EVs aren’t at the sales volume to easily amoritize it yet I don’t think.
Another thing is all the damn tech they feel the need to shove in ’em. Tis a scant selection of EVs that don’t come with every bell and whistle they can shove in and crank that profit margin.
I do agree with everything you said, except the raw materials. Lithium is down 76% since 2019. I should know, I was stupid enough to listen to Elon and bought a bunch of lithium mining stocks.
Never buy stock in the extraction companies. The real gains are further down the value-add pipeline.
Didn’t realize that, I shoulda probably checked my numbers first. And hey I was stupid enough to think I could make money on that AMC run-up even though I knew that it was gonna crater sooner than later. Turns out it was even sooner than sooner, who’d have thunk it.
Economies of scale. That’s how. Otherwise, no friggin way.
Well this is a Mercedes, which isn’t cheaper than an EV.
But in general, automotive transmissions aren’t that complicated, and you can get an idea of how much these things cost by the replacement cost: you can buy a whole drivetrain(engine, transmission, diff) for under 20k for anything short of a new diesel pickup, and probably under 10k for some cars. Obviously parts counters aren’t wholesale, and manufacturers pay less.
At $150/kWh, it doesn’t take much for just the battery in an electric car to cost as much as the whole drivetrain of a gas car, and that’s not counting the BMS, battery cooling system, or any effects regarding economy of scale.
ICE cars are cheaper at the moment because the R&D has been paid for and the supply lines are well established, benefiting from economies of scale. As EV platforms get deeper into the R&D cycle and increase volume, that simplicity will really start to pay off.
The title says its not for backward racing, but nowhere in the article does it say don’t do it.
And since you apparently have a vehicle so equipped, I think you need to see if you can get your car to do a 1-2 shift in reverse.
My theory is you start off in normal mode, then, just before redline (in reverse), you switch to snow mode.
We expect video by the end of the week.
I’ve heard that *some* will shift in reverse, MAYBE…
not sure I have a safe space to test this
Remember, safety third.
2nd gear start is weird, I’ve never wanted it in high range in my GX or my Land Cruiser. It really shines in low range letting you bypass 1st, but I’ve never understood its value as a low traction ratio for snow. In all my years with manuals in the snow, I never started in 2nd
I’ve never used the “2nd STRT” button in my GX, but I have used 2nd gear with a manual in when I lived in the upper Midwest. The specific situation was when the snow would hardpack during sub-zero temps into that odd snow/ice hybrid. Otherwise, I’m with you, starting in second wasn’t a normal part of my routine.
I use second gear in manual and auto transmissions a lot in snow. It’s great for getting through deep ruts or when the city plowed in your street-parked car.
The only time I recall starting in 2nd was with an automatic in temps so low that the snow would melt under the tires and immediately refreeze as ice, allowing the tires to spin without throttle in the little depressions they had dug out for themselves. Still needed the help of kitty litter and starting in 2nd to get out.