Hello,
I just recently did an 370z upgrade kit on my 05 350z 35th anniversary. I bought it off Z1 so it came with the extra bolts and nuts that fit specifically for the upgrade. When I finished everything seemed okay so I went to test drive it. As I reached about 40ish mph and let off the gas to coast I would hear a thunk or thump noise few times and it would go away once I go below 40MPH. I got home and inspected it and saw there was a little play with both axels but it wouldn’t move the nut. I don’t know if that’s normal as this is my first time with an upgrade kit. Upon further inspection I noticed where the axels and rear differential meet the differential has some play to it. I also don’t know if that is a normal thing. I’m trying to see what advice I can get. I did have a problem with throwing out the 350z wheel hubs so I upgraded to hopefully fix that problem. I also changed the ebrake pads and hardware since everything was taken apart.

 

It would help if you described WHAT a "370Z upgrade kit" is? Not everyone knows. Like me.

 

I think he means changing out to 370Z axles and hub/wheel bearings. I seem to recall a few threads about this after people swapped out to an aftermarket LSD.

Found the kit: https://www.z1motorsports.com/rear-h...t-p-15444.html

And this thread: https://my350z.com/forum/autocross-r...on-a-350z.html

 

If your original axles were damaged and you're noticing weird play in the connection, then you have a differential problem. it will probably just wreck those axles also. you need to repair or replace the diff.