i have an 03 discovery and the left rear air suspension assy failed, i took it to the dealer and they told me both air suspension springs must be replaced when only one failed, is this true or am i being duped into buying both. any responses are welcomed

 

I don't see any reason why the other air bag MUST be replaced at the same time. However, if one fails the other one might not be far behind due to age. If you want to get rid of the airbags you can install coil springs.

 

Yes, they must both be replaced, cause as thy age their ride quality changes and if not replaced in sets it will not ride the same.
How many miles on your truck, how mechanical are you?
If the bag is the problem, you should buy from Arnott Industries, their bag are cheaper and far better, with a lifetime warranty.
PM me your tele number and I'll call you.

 

Changing only 1 airbag is not good practice imo, you would never change 1 shock or coil spring would you ?? (I hope not)