Don't know if this is a right place to ask this. So I know there's a difference between 4WD and AWD, and the difference being AWD has equal power distribution between front and rear axles right while 4WD might have uneven ratio (e.g. 20% front axle and 80% rear axle) right? As I understand it. Now also a car might have a diff lock - so both wheels on an axle rotate at the same speed. Usually rear diff has a locking feature right? I think I've never heard about front diff lock. Then, there's center diff lock which makes two wheels on different axles rotate at same speed. So I wanted to know if there is a "true" diff lock which locks both wheels on both axles effectively causing all 4 wheels to rotate at same speed? Has this been done at all? Or is it too compicated to implement? If I were to go to a local junkyard and pick up a bucnh of axles and diffs could I fabricate something like this?

Thanks for reading my nonsense lol

  • Unimogs have 3 locking diffs, so it can move with only 1 wheel out of 4 having traction. Are you only considering mechanical systems or hydraulic as well? What systems have you found so far? You list some terms (awd, 4wd ...) but what technologies exist in the transfer boxes?
    – Solar Mike
    Dec 5, 2021 at 14:47
  • Hi @SolarMike I'm not really "considering" or "have found" anything at all really. I just randomly had this thought casue I drive a Subaru and it has AWD but doesn't have any diff locks but most SUVs that have AWD also have diff locks (rear or center). So I was just wondering if it was possible to make a "true" locked AWD so all wheels rotate at same speed
    – J. Doe
    Dec 5, 2021 at 14:53
  • Yes, a lot of "wanna be" suv's have 4wd but not many with centre dif locks or limited slip difs... The cost compared to the use... Those who really need 4wd compared to the hairdressers in Chelsea..
    – Solar Mike
    Dec 5, 2021 at 15:07
  • Welcome to Motor Vehicle Maintenance & Repair! Dec 5, 2021 at 17:58

1 Answer 1


The main difference between 4WD and AWD is that AWD is full time and 4WD is selectable, meaning you can set it to 2WD with a flick of a switch (well, on most modern vehicles, anyways).

Most AWD/4WD options available from the factory have a bias, meaning they usually set the rear wheels to have more power than the front. Some have a direct 50/50 split, but this isn't usual. Some even have more power towards the front. It's all dependent upon how it is engineered, designed, and the need.

You can get front or back differentials with a limited slip. You can also get them with a locker, which means there's no slip between. Some manufacturers use the ABS system to modulate the brakes, which slows down a wheel with less traction, which pushes the power out to its opposite partner. There's a wide range of how any of this can work.

If you go to a junk yard, yes, you could get everything you need to make the setup you're asking for. You'd probably have to go to several junk yards to find everything. Secondly, you'd need to do your homework to figure out exactly which pieces/parts you'd need to make it happen. If you went the a junk yard and asked for a transfer case which allows for front bias, they'd look at you like your nuts and ask you, "Which vehicle are you looking for?"

You can get a lot of stuff brand new in the aftermarket, if you look for it. It will cost you money, but realistically you'll get better parts/pieces for what you're asking about. They are usually built much stronger and resilient than the OEM counterparts, plus you can fit and massage them to fit different applications much easier.

  • Thanks. So there isnt any commercially produced vehicle with this kind of system right?
    – J. Doe
    Dec 6, 2021 at 13:45
  • You mentioned a bunch of different "systems" ... which are you asking about specifically. And more than likely, yes there is one, it just depends on exactly what you're asking about. Dec 6, 2021 at 15:11

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