As a claim adjuster I am happy to see that you are obviously a rationale and educated person when it comes to what the insurance company owes. My life would be a lot easier if more people where like you.

AS you just learned the hard way. You should only use shops that you or a close friend/relative are familiar with. Shops that are tied too closely to insurance companies have a habit of doing repairs like you got stuck with.

I have never handled claims in NJ so the info below is of a general nature. Take it for what it is worth.

1. If you haven't already done so call and ask for the Regional Claim Mgr and politely explain the situation and request that a Geico reinspector come and check out your truck. If that doesn't work mention that you will be filing a complaint with the insurance commissioners office. The commissioner's office won't do a thing to help you on repairs issues, but they will make GEICO (probably the mgr you are talking to) file a written answer to your complaint. The mgr will know that the commissioner's office won't help you, but they hate answering complaints. They take a ton of time to answer and they suck. they mgr might give you a break just so they don't have to screw with the answer to the commssioner's office.

2. Most insurance companies who have "preferred body shops" also provide some kind of written guarantee that says if the used (or LKQ parts = Like Kind & Quality) aren't good they will replace them. I would use this to get another rear axle or maybe a brand new one. It won't hurt to try to use the argument that the repaired axle is a safety hazard.

3. It is also a good idea to have another shop check out the axle and leaf spring and provide you a written report. It might cost you some money to do so, but it might get you the documentation that you need to get another inspection or axle.

Good Luck