The first issue is that my battery is always dead. I've it load tested and recharge amd they say the battery is good. I have an app on my phone that says the battery voltage is at 11.6 and dropping even with the new battery. Can it be the alternator? My second issue is that every time I'm going 50+ mph, when i let go off the pedal, it feels like something that connected to the wheels feel loose, what can that be?? Any help is appreciated. Thanks

 

If the voltage is dropping with the engine running, it could be the alternator or its wiring.
The looseness could be play in the differential, it can happen when you rack up the miles.

 

 

There's a lot of articles about battery testing.. get a multimeter and start testing away. Lookup parasitic drain.

Check your bushings if you hear a clunk at 50+ when you let off the accelerator. I had a bad rear bushing on a control arm that was causing mine to clunk. You can try putting it in park and getting someone to move the tire forward and back with force while you peek underneath.