engine and drivetrain Drive Shaft Questions

[ryanO]

I've recently developed an annoying vibration that seems to come from my drive shaft...

At 20mph I get a low rumble

At 40mph it's not so low...

At 55mph it's damn annoying...

Im scared to hear it at 75...

I have a few questions:

The center bearing is obviously the stock unit and has never been replaced.

How often do these go bad?

How difficult is the replacement procedure (1-10 scale)?

How often does the U-Joint go bad?

I had the car on a lift a few weeks ago and it looks like the U-joint is a bit wonky. No free play in the prop shaft, but it looks like one of the bushings may be blown out...

I've seen people selling the U-Joint and wondered what was involved in the replacement procedure... I'm assuming a drive-shaft shop would be involved in the balancing, etc...

Also, in searching the forums, I've found that people claimed to have a smoother running engine with the 320 Alternator upgrade. I'm running an original '02 alternator and having issues with lights dimming and gauges fluttering. Would a new alternator help with these issues?

What are the other benefits?

[TJs692002]

I rebuilt my driveshaft last summer. Before I did so I only hade a really loud nocking around 2000-3000 RPM's. My center carrier was complete demolished, no rubber left what so ever. After the swap the vibrations went away.

I also swapped out the stock alt and used the 318i conversion. The process was very easy but the motor does not run and different because of the new alternator. My lights sure are brighter at night however.

I also live in Sac, if you need any help with your projects look me up, I can be of some assistance.

[Mike Self]

1. rear tranny mount (replace with more robust unit from a 320 or a Bavaria)

2. As pointed out, center support bearing

3. rear U-joint going bad

4. physical damage to the driveshaft itself (dent, bend etc)

5. (not likely but possible) bad engine mount(s) misaligning the drive shaft

happy troubleshooting

mike

[c.d.iesel]

The center bearing is obviously the stock unit and has never been replaced.

How often do these go bad?

How difficult is the replacement procedure (1-10 scale)?

How often does the U-Joint go bad? = 1 to 28 years depending on it's alignment, level of abuse, missing heat sheild and over heating of the bearing and rubber, and just normal wear

I've seen people selling the U-Joint and wondered what was involved in the replacement procedure... I'm assuming a drive-shaft shop would be involved in the balancing, etc... = if the needle bearings in the cross u-joint are shot - send the drive shaft to any of the speciaist rebuilders

listed in ROUNDEL magazine

Also, in searching the forums, I've found that people claimed to have a smoother running engine with the 320 Alternator upgrade. I'm running an original '02 alternator and having issues with lights dimming and gauges fluttering. Would a new alternator help with these issues?

What are the other benefits? = it's battery voltag and charging.

12.65 for a fully charged battery, and 14 volts for a charging alternator.

A new battery and 2002 alternator will do just fine. 320i parts not required.

the 'smooth running' was fixed by other methods.

[Paul7002]

Add an additional ground to the back of yor instrument cluster