Unstable Unimog


New member
I have a Unimog FLU419. It's been a great vehicle but when you lift off the throttle, the vehicle becomes unstable, wanting to swerve back and forth so it doesn't feel safe. When you apply throttle again it stabilizes. The more quickly you lift off the throttle, the more radical the swerving. It used to be very stable and it used to go over 50mph but now it only goes 40mph and has this swerving problem. The only change we've made is to remove the part of the fuel filter which appears to be a bypass of some sort. If anyone knows what is causing this I appreciate your input.


Hi Pat, and welcome. Usually if things get entertaining on overrun, it's to do with bushes... When under drive load, everything is pushed tight and the wear is not allowed to move, but the moment you back off the accelerator, the axles are then just floating under the vehicle, allowing them to move about producing the effect you describe... I'd be getting under the vehicle with a big pry bar, and flexing every suspension bush and see how much movement you have. Another thing to do is have a friend drive the vehicle slowly in 1st gear low box. get him to accelerate and decelerate... while you walk beside the vehicle (emphasis on beside at a safe distance). Look for movement between the axle and suspension arms. If there's excessive play, you'll see it.

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New member
It can happen with a small 4wd too, in my Defender, as soon as a rear trailing arm bush goes, you can get rear wheel steering sensation when on and off the throttle, not the best feeling on the highway. Sometimes a bolt has loosened itself but more often then not you need new bushes.