Loud drone/rumble from driveshaft/diff

[Sea Aych]

I just swapped out my automatic for a standard 5spd, and all is working perfectly, except from roughly 50-70kph (31-43mph ish, but speedo is insanely optimistic so i'm guessing here... it's basically from 3rd at 2500ish and up rpm to a low 4th gear) there is a loud low pitch drone/rumble coming from the middle/rear of the car. It doesn't shake the car much at all, just noisy.
Now the diff is exactly the same as before, so i'm not sure if it could be that.

Brand new CSB, perfect giubo, so i'm right stumped.
Any ideas?
Thanks all

[jlevie]

Could be a bad drive shaft.

[Sea Aych]

Could be a bad drive shaft.

Really? What indicates that so quickly?

To clarify, actually, the noise sounds like a low exhaust rumble, just at that higher speed.

[Steven]

What about wheel bearing? I had a loud drone I could hear in my car. It just randomly was there one day, once I replaced the rear wheel bearing (a bit hand a half) it was fixed.

[Sea Aych]

What about wheel bearing? I had a loud drone I could hear in my car. It just randomly was there one day, once I replaced the rear wheel bearing (a bit hand a half) it was fixed.

I would think that, but the weird thing is that the drone didn't exist before the swap...kind of confused.
It's coming from the back, now that i think about it actually, and sounds kind of like exhaust..but i think it isn't because it's not started by certain rev level but by a certain speed...

[ForcedFirebird]

Could be a bad drive shaft.

Really? What indicates that so quickly?

To clarify, actually, the noise sounds like a low exhaust rumble, just at that higher speed.

Check the play in the universals. The drive shaft had to be changed during the swap, noise is coming from drive-shaft area, have a feeling Jim may be on to something.

It's often the rear u-joint, you can reach it fairly easily to check for play.

[Sea Aych]

^^ hmm, okay, i'll give that a look at tomorrow.
Still have to change the tranny fluid since it hadn't while the manual box was sitting for a long while before the swap, so maybe that has something to do with it too. Or am i completely off?

[TSI]

Likely CSB or shaft. CSB had to be preloaded 5mm, was that done? Was DS checked for binding joints? Was your diff fluid changed too (don't do this at home)?

[Sea Aych]

Was your diff fluid changed too (don't do this at home)?

Heh i recall...
Anyway, CSB preloading might be the issue. i jsut read that a few people didn't do it and get shakes from 20-40mph.. similar but with noise with me... I'll have to check

*edit: then again, it's not a vibration...just noise

[dwight]

While driving put your right hand down on the drive tunnel, also go about 30MPH put car in neutral and make some wave turns could be CV or bearing.

[Sea Aych]

While driving put your right hand down on the drive tunnel, also go about 30MPH put car in neutral and make some wave turns could be CV or bearing.

Turned out not to be that thankfully.
CSB was properly preloaded too. I'm starting to think it was just a balancing issue with the driveshaft since it had to be taken apart during the swap. It had no issues before, so maybe it's off plane by a spline or two, which would explain why it resonates through the car at certain speeds only.

[Sea Aych]

Update: Finally got the car up on a lift, got the CSB loaded properly and changed the transmission oil to MTL. It made a slight difference, but the noise and vibration is still there in that 20kph/12mph window.

Found that a couple of the seals in the U joints were starting to go, and that there was verrrryyyyyy slight play. Could that small amount of play be the cause of the vibration/noise or would it be much more noticeable? I'm starting to think the DS is toast. and i'll need to scan for a new one

*EDIT: found the white dots and they're lined up perfectly too..

[ForcedFirebird]

Don't go by the white dots, they are just for reference so you don't get the two halves 90* out of phase. The front/rear u-joints need to be square to each other.