Tumbling/viabrating at 3500-4000rpm

Hey ive noticed that when i get up to about 3500-4000 it feels like the driveshaft is about to fall off or something there is this crazy rumble/tumble kind of sound and feeling comming from near the back of the car. It’s especially bad when im on the highway because cruising speed is withing 3300-4000rpm for me on my sr20.

so any ideas? a couple friends said it might be the driveshaft mount or something or even a twisted driveshaft? it runs smooth in all rpm ranges except between around 3500-4000rpm. thanks.

its a 92 hatch, hicas was disconnected and locked.

Hey ive noticed that when i get up to about 3500-4000 it feels like the driveshaft is about to fall off or something there is this crazy rumble/tumble kind of sound and feeling comming from near the back of the car. It’s especially bad when im on the highway because cruising speed is withing 3300-4000rpm for me on my sr20.

so any ideas? a couple friends said it might be the driveshaft mount or something or even a twisted driveshaft? it runs smooth in all rpm ranges except between around 3500-4000rpm. thanks.

its a 92 hatch, hicas was disconnected and locked.