Loud Vibrating sound in rear! What's the deal?

[Hrududu]

This morning I'm leaving my house to go to school. Everything is fine for about 5 minutes, then I started hearing this loud vibrating sound coming from the rear of my car (not in the very back, just in what sounds like the cargo space). I was driving at 55mph in 5th when it started and it happens as long as I am in gear. It goes away when i push in the clutch, as as I accelerate. Once I reach a steady speed, the noise grows louder. I swear I didn't do anything. I was driving very easily, and this just started happening. The only thing I can think of, is when I had traveled about 2 blocks from my house, i heard what sounded like something falling onto the passenger floor. I disreguareded it at the time becuase I just assumed my brother had dropped something, but he said he didn't. Please help me. My car is falling apart more so every day, and I'm out of $$.

[EScanlon]

Check the connection of the driveshaft from the tranny to the rear differential. Also check the connection of the half shafts to the diff.

I had something similar years ago and it was the bolts on the half-shaft that had loosened and allowed the half-shaft to fall out of alignment. Then when I would begin rolling, they would rattle due to the mass of the shaft being out of center with the center of rotation.

Check it soon, in my case it caused the Left Rear wheel to come off at 65mph. Believe me it is NOT a sight you want to see.

E

[MikeW]

Check the connection of the driveshaft from the tranny to the rear differential.

I once had the rear driveshaft connection to the differential come loose and experienced horrible clunking and vibrations. As I recall three of the four bolts came out and the fourth was loose. While I wouldn't want the rear of the driveshaft to drop at highways speeds I suppose that would be better than dropping the front. I saw the MythBusters episode where they caused the front to drop right into a carefully prepared pothole ...

[PrOxLaMuS©]

All of my bolts came loose this week on the driveshaft... whooops...

fixed!

[First Gen Z]

If you don't find anything on the outside check the inside of the diff. I've heard the roll pin that holds the pinion shaft in place can shear and allow the pinion shaft to fall out of place.

[EScanlon]

If you don't find anything on the outside check the inside of the diff. I've heard the roll pin that holds the pinion shaft in place can shear and allow the pinion shaft to fall out of place.

Ok, now I'm no transmission / differential mechanic, but how would the car run?

1¢

E

[=Enigma=]

Many many years ago I was at auto race at Laguna Seca, I can;t remember what kind of cars they were but I think it was a GT race of some sort. This was before the redesign of the track when turn 1 was a long sweeper that tied into what is now turn 6 on the back side. In this format the sweeper was 1/4 mi+ and speeds during this race were upwards of 140mph+. About half way through this section at close to 100 or better, a car dropped the front of the drive shaft onto the track, it caught and launched the car about 30ft into the air and it did roughly 6 end to end flips before landing and doing a few more. This is the most spectacular crash I have ever seen either in person or on TV to date.

[First Gen Z]

I know of two ZX differentials that self destructed because the pinion shaft fell out of place. The shaft obviously wont come all the way out but it will come out far enough to make loud noises and create bad vibs. The guy that owned the car replaced the roll pin with a solid pin and welded it in place.

[sideshowbob]

My diff makes a bit of a click and, well, not exactly a grind but a rumble when the driveshaft is turned by hand. The free play in the driveshaft is a few inches, is this normal? Oh, and it has the infamous 'clunk' too.

[beandip]

NO ! Not close to normal. I bet it has a clunk. I think you need a new punkin . I dont remember , do you have a 240 ? If so and if you dont want to make a drastic change in gearing and would like to have a bit better off the line . Find a automatic z they have 3.54, you most likely have 3.36s . Not a tremendis difference but it will be noticeable. Just a thought .

[sideshowbob]

It's a 280. I'll add it to the list Maybe it's salvageable.

[sblake01]

Ah, back to the original topic. Like mentioned above, check the driveshaft to differential mounting bolts. My car developed this malady a couple of years ago and it turned out to be simply loose bolts.