Getting something to give

[b*saint]

I have a bearing or whirring noise from the drivetrain coming from my car. Its been going on since the summer. It comes and goes. It whirring constantly at 40 for weeks then all of a sudden it'll be quiet. Its back and better than ever. No matter how hard I beat on it, nothing breaks.

It sounds like its come from the rear now and my wife says the rear left so I am thinking it might be a bearing now. But it doesn't change with weight load, it changes with power load input. It also sounds pretty metallic but it quiets up on the highway. The whirring comes mostly when the temperature fluctuates a lot. Like Monday it was 55, yesterday it was 23 and it started up again yesterday.

Anyways I gotta get it to give. How do I blow up a bad diff?

[Kershaw]

replace the oil with nitroglycerine and go drag racing.

[Dmcastino]

I hail originally from the world of Jeeps/offroading and we have a lot of experience with blowing diffs :). They are solid axle, but I am going to assume the principle holds true for anything, its simple enough. Basically what will ruin a diff (like I said, at least with solid axle vehicles) is a sudden amount gain in traction when previously there was little or non. For example, when offroading, letting the rear end bounce when trying to get up an obstacle is a real drivetrain killer: you lose all your traction as you rear end bounces into the air then when it comes back down on the rock and you gain your traction again.. BOOM, there goes the diff or an axle shaft or a driveshaft etc, you will find out what your weak link is real quick. Obviously you cant really bounce your e30, but I'm sure you can find ways to have a lot of wheelspin and suddenly gain traction... haha. Only problem is there is no way to guarantee your diff is gonna be what gives up the ghost. Do you have an LSD or is it open? If open it might help to get one tire spinning real fast rather than both then gain traction as I assume that would be hard on the diff.

Again, take all this with a grain of salt as I am relatively new to the world of E30s, but I have definitely been around a few differentials when they grenaded in other vehicles haha.

[Kershaw]

drain the oil, fill it with gunpowder.

drill a small hole through the filler bolt, just large enough to feed a fuse through, put the bolt back in. put the fuse in.

light the fuse, get back in your car, and see if you can out drive the explosion.

[Eecen]

Just keep driving as is. Makes your car sound boss mang.
My eta had a growling diff for like ~3 years, never gave out. Just turn up your music.

[b*saint]

Yea the car feels solid still. Fucking BMW. You can't blow them up.