I can’t really remember exactly why we were talking about it, but for whatever reason David and I ended up talking about front-wheel drive layouts. I think it was triggered by the realization that the Dodge Intrepid was a longitudinal FWD design, which, buy modern standards, is pretty unusual. That, of course, made me think about other longitudinal FWD cars, like Audis and Citroën 2CVs, and then the other kind of longitudinal FWD, where the transmission is in front, like Saabs and Citroën Traction Avants and and Cords. Anyway, it got in my head, and the only way to exorcise thinking about this is to rope all of you poor bastards into it. So, with that in mind, now I’m curious and desperately want to know this: do you have a favorite FWD layout?
Here, let’s walk through all of the FWD layouts I can think of; I tried to include all of them, including at least one that I don’t think has ever been tried, because of stupidity. So, here we go, time to evaluate and see what grabs you, deep and tight:
Okay, these two transverse-engine versions, just mirror images of one another, are by far the most common FWD layout – and, most likely, the most common drivetrain layout of any kind on the road today. I suppose the original Mini is a bit different, in that it has the transmission below the engine, but it’s pretty much like these. Their biggest advantage is most likely packaging; it’s a really compact and space-efficient design.
This layout is perhaps most commonly seen now in Audis, and lends itself well to having all wheel drive variants. It does push the engine very far forward, making the car pretty nose heavy, but there are plenty of great-handling cars that use this method despite the seemingly very understeer-y layout. It’s less space efficient than the transverse version, but you still don’t need a driveshaft, so it’s not too bad.
I always liked this sort of layout, probably best known in Saabs, because it forces a front-mid engine layout, which I’ve always been a fan of. It also lends well to a sloping hood and easy transmission access, though getting to the spark plugs on the rearmost cylinders can be tough.
Okay, those are the mainstream options. Let’s look at the weirder stuff:
Now, this just seems bonkers: rear engine, front drive. This seems like a layout specifically designed to find the worst qualities of every layout: you still need a driveshaft, you have to deal with rear-engine oversteer, and you get none of the traction benefits of putting the engine over the drive wheels. There seems to be zero reasons to try this, yet it has been tried a few times! Never successfully, but I did once catalog all the loons who tried this for The Old Site:
Why do this? I have no idea. Maybe some kind of latent distaste for rationality, I get that. I suppose you could also do this with the transaxle up front:
Would that be any better? Maybe a little, but not much. At all. It’s still ridiculous. I suppose technically the Dymaxion may have actually been rear-mid, front drive? Oh jeez. Fine, let’s make one of these for that absurd layout:
I’m not making a transaxle front version of this, though, because it’s never been done since, you know, it’s just that stupid. It’s got all of the problems of the rear-engine/front drive layout, but with worse packaging. It’s kind of achingly beautiful, in that miserable way.
Okay, one more weirdo, this one was actually attempted:
The legendary T-Drive! This was a design attempted by Ford to accomplish something I can’t imagine anyone actually asked for: shoving a straight-eight engine transversely in a Ford Tempo.
They did manage to do it, by tapping power from the middle of the crankshaft instead of either end. It’s bonkers. If there was a good reason to do this, I can’t figure out what it might be. But I’m glad they did it?
Everyone got all of these? Take a moment to really consider which one moves you the most. Technically, emotionally, erotically, all of it. Time to vote!
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I prefer the diagonal FWD option where the crank has a bevel gear on it’s output.
Jason, you seem to have forgotten about the UPP systems in Oldsmobile Toronado (1966–1985) and in Saab 99/90/900 (1968–1998).
Both have longitudinal-mounted engines with gearboxes and differential gears mounted in parallel along the length of the engines while Oldsmobile uses the heavy chain and Saab series of gears to transmit the power to the gearboxes. The former has the flywheel in the rear with the differential gear in front of gearbox while the latter has reversed their positions.
I think this system is the best compromise of offering the ideal front-rear weight ratio, eliminating the torque steer, reducing the massive “overbite” common with the transverse-mounted FWD cars, allowing the ease of maintenance, and so forth. I despised my Buick Skylard (yes, spelling is intentional) and Chevrolet Celebrity for their nose-heavy handling and braking, frustrating experience of replacing the spark plugs in the rear bank of V6 engines, etc.
Mercedes-Benz used the unique layout for its first two generations of A-Class (W168 and W169) and B-Class (W245): engine mounted behind the transaxle and tilted extremely forward so the whole system would slide down underneath the floor plan in an event of frontal collision.
Well, the choice of image for the article much spoiled it for everyone; that’s the unequivocal best FWD layout in its finest application ever.
Just arrived from a 100km trip at the wheel of that very front-mid layout in its 1108cc, 34hp guise. It never ceases to amaze me how nimble the Renault 4 is. Mine cruises effortlessly at 70mph, but if I step on it on flat sections of highway, like I just did, it will go a bit over 80mph. Although admittedly, at that speed, the engine is no longer running effortlessly, and I try not to drive it that fast for long stretches, but I really have to take my foot off the gas to make sure I don’t go over the speed limit.
How is this related to the engine layout? Well, I could be wrong, but in a car that light and with a drag coefficient of “no, thanks”, the engine placement probably helps with weight distribution, making the car more drivable and the ride a bit less harsh. But mostly I just went on a tangent because I can’t help myself from spreading the gospel of the Quatrelle. Front-mid goooood.
Oh, and nice touch, using that Renault 12 template for the layout examples.
Is the Lancia Fulvia longitudinal withtrans behind? With the engine canted to the right, I am not sure.
I posted too soon. Found my answer. (Yes)
Did you miss one? The classic Mini has the transmission directly under the engine, sharing the engine oil…..The Ferrari Dino did the same with a rear mid engine version.
I had an Intrepid ES as my first car bought as an adult. I loved that car. For a GenX kid who drove 130 odd hp V8 80’s Fords and K-Cars it was a marvel of power and handling. (215!! That’s almost as much as my buddies old Mustang Gt!!) Great on trips, decent on mileage. I got the auto stick for the tranny cooler and always made sure to put in the right Trans fluid. I finally traded it after 10 years and 200k miles. Only things that went bad was the tie rod ends at 110k and the water pump.
I still love that car.
I think the reference is to Saab 99/900. I thought those transmissions were underneath the engine with the engine facing backwards (power takeoff at front of car). 9000 was transverse, Sonnet and earlier longitudinal with transmission behind.
I voted transverse-transmission on the left mostly because its proven to be a relatively easy combination to do maintenance on, its nice and compact, and it doesn’t shove the engine too far ahead of the axle (at least when paired with I4 engines, which is where my experience lies).
Conceptually, I really like longitudinal, transmission front as well, since it provides the stability benefits and most of the traction benefits associated with FWD with a low polar moment of inertia, a bit more rearward weight bias, and a “wheels-at-the-corners” aesthetic. I didn’t own my Saab 900 (OG) long enough to have to do any maintenance though, so I can’t speak to that aspect of it.
For the Transverse – engine left and engine right images, typically the engine is pushed forward of the axle center line a bit and the differential is offset backwards so that the driveshafts are in line (or as close as possible) with the wheel center line to avoid large CV axle angles or that awkward jog you show getting around the engine.
That T drive has me thinking… you should be able to develop an inline 16 with a T drive. One of the limiting factors of going beyond a straight 8 is crankshaft torsionals and whip, with the load being applied at one end of the crank and farthest cylinder applying power. But, in a T drive, you’re pulling power from the middle, so each half of the crankshaft would be equivalent to a straight 8.
Pretty sure the only vehicle that would fit in is a Canyonaro, cuz it’s 2 lanes wide.
The crankshaft torsionals won’t be so bad on a straight-8 with T-drive since the flywheel inertia and power-take-off will be in the center of the crankshaft, not at one of the ends. Therefore, it’ll act more like two I4’s than an I8 since the torsional damping happens in the middle and the furthest away that the pulsating torque load (cylinders only provide positive torque during the power stroke of their 4-stroke cycle) is being applied from that damping is only 4 cylinders, not 8.
That’s exactly what I was thinking. Straight 8’s were around for quite a while with traditional flywheel placement, but going for more cylinders was problematic for all the reasons we both described. But, if you’re going to pull power from the middle, now you can essentially have two straight 8’s back to back and still only be at the engineering limits of the straight 8. I want my T-drive straight 16, dangnabit.
Well, looks like we’re all idiots lusting after a T-Drive.
Jason, you forgot one!!!
The Engine on top transmission at the bottom in the oil sump, both sharing the same oil used in the classic Mini!
He did mention it, but I figure if he’s going to differentiate between transmissions on the left and right, then ‘underneath’ deserves it’s own category too.
I guess it’s also pretty common in motorbikes as well?
But surely FWD motorbikes are not that common.
I think it was one of my Citroëns or Peugeots I was under to fix an oil pan leak, when I noticed a drive shaft going THROUGH the oil pan! Oh, those frenchmen 🙁
GM did this with the GMT360 trailblazer/envoy/ranier/ascender/bravada/9-7x with the outstanding 4.2L I6.
None of the above. My favorite FWD Layout is that of the Bond Minicar.
1 Wheel FWD with two undriven wheels in the rear.
With a proper steering design setup you wouldn’t even need a reverse gear, just turn the front wheel 180 degrees and you can go in reverse.
Such a layout also gets rid of one of the main disadvantages of FWD which is the limited steering angle which limits the turning circle. Turn the wheel 90 degrees for an obscene turning circle.
Drove something like this at the county fair when I was a kid. It was even an EV.
This is where I would insert a picture of a bumper car but I don’t know how to do that on this site.
I’m going for the 2cv set up. Make changing the clutch a pain but I replaced a motor in an afternoon using a Chiltons manual, on my own with no hoist.
I also loved being able to lug a 2CV engine round all by myself. And playing wheel barrow when moving the frame around 🙂
The rear engine front wheel drive layout did show up in a 60s young adult book. I think it was written by William Campbell Gault who turned out a bunch of racing themed books that filled most of a shelf in my middle school’s library.
I don’t care as long as it’s easy to work on 😀
the olds and caddy front drive with the motor over the axle seems to be the most compact and best design as a result, strange they never used this trans and made an AWD caddy back then.
The Unitized Power Package – fantastic bit of engineering. Basically eliminated torque steer from those big, torquey engines, allowed the same drivetrain components to be swapped around and shared directly between RWD and FWD applications, and was totally modular – bolt it into a motorhome if you want. Plus, lent itself well to the classical long hood/short deck proportions appropriate for luxury cars.
None of the above. I prefer FWD transverse, transmission below. Sharing the same oil as the engine. BMC Mini and its descendants used this setup.
Ah, the ol’ motorcycle-style unit construction. Did those use a wet clutch?
Subaru is longitudinal, engine in front.
Just surprised no one had mentioned it yet
Subaru isn’t FWD. It’s AWD 😀
(Yeah, I know they still make FWD for overseas markets)
Pre ‘94, AWD was an option in the US. I’m on my 4th Subaru (“Subaru”—GR86) and none have been AWD. Having driven both versions of my respective cars, the FWD ones drove MUCH better with better mileage and performance (especially important when the GLs only had 73 hp and my mk1 Legacy wagon was about as quick as the AWD turbo sedan while feeling more eager in spite of the tallest FD of all the versions). I stopping buying when they went AWD only. That and they got heavy, requiring the EJ get stretched to 2.5 liters and that engine in that displacement sucked.
My first Subaru fling was a 2wd ‘82 GLF sedan, so I easily forget that they want to be known for their symmetrical awd in the US.
Did any mfg ever do a transverse engine with the transmission in front of, or behind, the engine, in parallel? Kind of like Ford’s T-drive, but the engine could still be coupled to the transmission at one end or the other.
How did Lamborghini handle the transmission in the Muira? Since it was a transverse V12, I can’t image they could fit the transmission left or right of the engine. Yeah, I know it is mid-rear, but still a similar concept.
I believe the Miura was a T-drive as well.
Not sure how the Muira transmission was located, but its easier to do wide engine-transmission packages in the rear since the rear wheels don’t need to turn and therefore have a smaller “envelope” of motion (mostly just up-down with suspension travel, some front-back with deflection from bumps, etc).
It was underneath with the diff on the left. Originally, it shared the sump. This wasn’t a wise idea, so they were separated later.
Dammit, no edit—power takeoff on the left. Differential was centered with the block.