Cylindrical constant accelerating both sides of the wheel

Ok so I had some troubles with making tank bogies, I need the wheels to each be on a level so they deform to the terrain, it probably easier to show you what I mean.
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Problem is when the wheels accelerate it forces them to get closer together no whatever what I try I can’t fix it. (ignore the weld you can see it just connects two mesh parts as my modeller made them separate), if its any help I want to recreate this.

My problem is what happens when I hold S, it lifts the backwheels into the air.