roughness from 35-50mph

[Recian]

So I've had this in the car since I got it. It's a NA car. Tires were choppy so I assumed it was tires. Put new tires on the car and it's still doing it. Starting at 35 regardless of what gear the car is in it's just rough til about 50 and it smooths out. Idk how to describe it. Swaying doesn't change it so I don't think it's wheel bearings. It feels like a bad bearing. It feels like riding in a truck with mud tires with too much tire PSI. Knobby/rough feeling. I'm wondering if I should look into rear end or diff center bearing? Any common issues?

[t.mcginley.jr]

My money is on the driveshaft carrier bearing going bad. Do you have a stock 2-piece driveshaft?

[t.mcginley.jr]

Or whoever put your tires on did a terrible job balancing them.

[Recian]

Yea driveshaft is stock and the car has some rust underneath from being in ohio. It smooths out over 50. I had it before the tires. Did the tires on road force machine and all. I know now bits not the tires.

[t.mcginley.jr]

If you can, jack up the back of the car so that you can see the driveshaft. Assuming you have the stock 2-piece one, there will be a carrier bearing in the middle that looks like this:



Grab the driveshaf and try and shake it. If the bearing is good, it shouldn't really be able to move too much, if at all.

[300zxstanced]

+1 with the driveshaft bearing, vibration typically comes from or is associated with rotating parts, especially if it comes and goes at certain speeds. Also do you feel the vibration in thru the seat or only in the steering wheel?

[Recian]

That's why I thought carrier bearing. Its felt in the seat/floor and is speed related. Just didn't wanna spend 400 on a driveshaft in a guess

[t.mcginley.jr]

If that is the problem, you should just get a 1-piece replacement one. EP Racing sells them for $235 or so I think

[Recian]

I'd rather do aluminum. Less rotating weight. Unles there's a benefit to steel.