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Is there a benefit to an AWD system without a transfer case?

For example, the Audi Quattro AWD system appears to direct power to the front wheels directly from the transmission. enter image description here

Whereas the Jaguar AWD system pictured makes use of a transfer case.

enter image description here

Aside from a hump inside the cabin floor, is there a downside to having a transfer case? Is an AWD system without the transfer case superior in any objective measure since the AWD system is internal and conceived at the time of design rather than bolted on later? This may include benefits in size, balance, performance, front-rear drive split, reliability, efficiency, etc.

For example, it seems to be that one of the negatives of the Quattro design shown is that the absence of the transfer case means the front driveshaft must pass through the transmission, pushing the engine ahead of the wheels and yielding a nose-heavy car, which may not be desirable for handling. However, the AWD components are integrated in the transmission possibly yielding more legroom in the cabin.


Here, Subaru has offered some of the pros and cons of the different layouts as part of a promotion for their system:

enter image description here

  • The job of a transfer case is to split the power, front and rear. On vehicles without a true (separate) transfer case, isn't the job handled by the transmission? Meaning, the transfer function is built into the transmission instead of having a separate piece of equipment. At least that's the way I was thinking ... maybe someone else has a better perspective. – Pᴀᴜʟsᴛᴇʀ2 Nov 15 '16 at 17:04
  • My main question is if having that functionality integrated confers a benefit over bolted on exterior units – Megatron Nov 15 '16 at 17:19
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    Maybe someone has something for you, but would bet it has to do with space and engineering concerns from the manufacturer. I like the question, though! I personally don't have a definitive answer for you. – Pᴀᴜʟsᴛᴇʀ2 Nov 15 '16 at 17:31
  • One benefit of no transfer case is that there's no need for a front driveshaft. Not sure what you are looking for here man. There sure has been a lot of theory questions here instead of the usual broken car questions... – cory Nov 15 '16 at 18:16
  • Thanks for the suggestion - edited. Since you suggest a few objective measures, do you by any chance know of benefits in these areas (eg. torque handling, durability, etc)? – Megatron Nov 15 '16 at 19:25
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Pros and cons of an AWD transaxle vs a separate transfer case:

transaxle pros

  • more compact system
  • lighter
  • less moving parts in general
  • less parasitic drag
  • allows the car to be lower to the ground

transaxle cons

  • less flexible
  • harder to repair
  • transaxle is not cost effective to use in a 2wd car (a lesser model of the same car for instance)
  • less flexibility in engine placement vs axle location
  • limited cross model usability, you probably won't see this system in a truck or SUV
  • added cost through design, development, tooling, testing, etc.

t-case pros

  • you can disconnect the front drive shaft and keep driving if there is an issue
  • easier to work on as all parts are usually individually accessible
  • allows greater flexibility in engine placement
  • uses standard transmissions for the production cars which can be used in cheaper 2wd models making the entire line less expensive
  • tcase and front axle can be used in many different product lines including SUVs and trucks
  • less expensive because usually its already designed, developed, tested, etc. not to mention its a small addon module to the back of the trans rather than an entirely new transmission.

t-case cons

  • heavier
  • more parts
  • more parasitic drag
  • axle needs to be outside and usually below engine and or trans raising the center of gravity
  • takes up more space overall
  • @Megatron you are welcome :) – Cc Dd Nov 16 '16 at 3:55
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There's no inherent increase in parasitic drag with a tcase vs an all-in-one setup. Assuming that you're comparing independent suspension full time awd you'll just have transaxles attached to the tcase somehow and also covering the job of a front differential . Solid axles with a tcase will require another differential but that's getting more into the 4x4 vs awd arena. I can see why it might seem significant, but in reality the difference in question is comparable to asking if a computer with a CPU built into the monitor is better than one with a separate tower. The answer is always "it depends". All the moving parts are essentially the same between both options. They're just either mounted in different aluminum cases, or instead sharing one. I prefer them separate so they can be more easily be replaced because usually the oem offerings Include weak performing lsd's if not open diffs, or some other money saving work around nonsense piggy backing on systems like traction control and automatic breaking to send power to the appropriate wheels. Most current awd systems are only good for slick roads and light snow. In the u.s. you're reasonably priced (<50k) quality options are limited to the lancer evolution, Subaru wrx, and a handful of basically impossible to find celicas, or imported rhd cars. That's just based on my personal requirements, and preferences for an awd system.

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