Hiya mate, stick at it, it will be worth it in the end
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The rear springs are not attached to the car, they just sit in rubber seats. That`s why people that have lowered springs can have the problem of the rear springs falling out when the car is jacked up
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I had the same problem jacking my car up (when it was lowered), a trolley jack wouldn`t go underneath. Either get a mate to lift the back of the car up a little so you can get the jack under, use the standard scissor jack to raise the back up a bit first, or invest in a good quality low entry trolley jack (whch is what I had to do).
I know it`s a pain, but keep going
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Regards,
Ian.