While reading the 'Mercedes Truck Front Axle Systems'


I was confused as to what a 'through-drive axle' means. This has led to some exhausting research, and the only related thing I've been able to could find is this:

Use the lock position only when you approach conditions where one or both wheels of an axle may slip. The valve locks the differential and causes it to act as a “through drive,” transmitting power equally to both axles.


Speaking of which, what is an 'interaxle differential'? Is it a physical part? If not, do 'interaxle differential' and 'interaxle differential lock' mean the same thing?

Kindly note I know absolutely nothing about trucks (and close to nothing about vehicles and their mechanics altogether). Simpleton language would be more than welcome :)

  • Welcome to Motor Vehicle Maintenance & Repair! Nov 16, 2018 at 22:41

2 Answers 2


A drive-through axle is the rear axle of a front pair of axles (or front axle of a rear pair of axles), designed so that the input to the first or front axle is also sent to the second or rear axle. This avoids the movement restriction and extra weight that is involved if there are two propellor shafts from the gearbox.

The interaxle differential allows for the difference in rotational difference between the front axle compared to the rear axle that is found on a twin axle set up. Same idea as a differential between wheels on the same axle.

An obvious example was the RangeRover that had the centre differential located as part of its transfer box - allowing for the difference in rotation between front and rear to be accomodated.

  • So just to make sure I understand correctly: if the vehicle has a dual front axle, the rear one of the pair would be called 'drive-through'? And if it has a dual rear axle, the front one of the pair would be called 'drive-through'?
    – Jawad
    Nov 16, 2018 at 22:25
  • Also excuse me because I have apparently made a mistake: it's 'through-drive' rather than 'drive-through'. I hope this doesn't make any difference.
    – Jawad
    Nov 16, 2018 at 22:29

If you click back one tab on your link on "Aggregates" the picture that appears explains a lot.

Also click on the subcategory "Axles" and "Integrated Drivetrain" for further details.

@Solar Mike was correct, but some of these MB vehicles have some AWD/4WD capability. The "interaxle" differential for the front axle is actually contained in the "sump" region below the engine.

The "interaxle differential lock" I believe in this case to be a system to "lock up" the entire axle and bypass any differential action. This is useful in low-traction situations, or if one front wheel in mud or ice or snow. It's a very popular Mercedes "European" kind of thing, and has been going on at least since the Unimog.

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