Referring to the rear axles.
Well, I don't have W124 info. On a W123 the spec that when you inert the axle into the differential and insert the C-clip that retains it the clip should go in and out OK and there should be no erectable end play on the axle.
If you have too much end play, there is (or was at one time) spacers/washers of different sizes to take up that play.
On the wheel bearing end of the axle there should be no end play at all where the axle goes into the control arm and wheel bearings. There is a bolt, washer and sleeve setup that controls that and it comes is accessed from outside and to the side of the real wheel hub.
Looks like the W124 hub/wheel bearing end is different. I think there is info here on that.
https://www.pelicanparts.com/techarticles/Mercedes-W124/95-SUSPEN-Axle_Replacement/95-SUSPEN-Axle_Replacement.htm
DIY W124 Rear Wheel Carrier Removal (Rear Wheel Bearing Change)