Please Help! Vibration in rear

OK - I am a total newb here, so be gentle. I have wanted a BMW for a very long time, and I bought my first one last night... a 1998 328i e36. During the test drive, I had noticed a slight vibration coming from the rear of the car, when the car was under throttle. It was noticeable, but not bad.

However, driving it home last night at highway speed (about 65 - 80mph), the vibration got louder and more severe. If I let off the gas, it completely went away and everything was smooth and quiet. When I would brake, everything was smooth and quiet. But if I touched the gas pedal even slightly, the vibration returned.

I am really scared that I made a huge mistake buying this car, and I can't do anything about it since I bought it off Craigslist. Other than that issue, it seems like a great car that I would be very excited about this morning, instead I am sweating big expenses to fix it. (and an angry wife. even worse.)

Also, I have almost no mechanical experience or ability. Fortunately, I have a friend that is a mechanic that works out of his own garage. He does have some BMW experience, and if I can tell him the likely problem, I am sure he can figure it out.

I have searched around the forums some, but I am reading various opinions for similar sounding issues. Please help, only if you are fairly sure that you know what might be causing this problem!!!

Thank You!

You could have flex disk for the drive shaft that has failed or a center support bearing . Either one is fairly normal and not to bad to replace. Check these first and hopefully you don't have a differential problem.

^

This exactly.

Yep, I'd check the flex disc, drive shaft center support, and also the drive shaft u-joints.

Dont sweat a flex disc. You bought a used car. Things will come up. These are reliable machines but used cars will have issues that will need sorting before your on easy street. Welcome.

How difficult is it to get access to these parts? (flex disc and center support bearing)

Thanks for the help!

Very easy.

I should have been more clear - How easy is it to get access to the location of these parts on the car, to evaluate what needs to be replaced? Thanks!

Very easy. The flex disc and center support bearing are clearly visible if you get underneath the car.

Cool - Thanks!

OK, so now that Winter is starting to leave, I am finally getting around to this vibration issue. I had the car in to my mechanic this past weekend to do the rear shocks, and I also asked him to check out the center support bearing and the flex disc. He said that the u joint is bad, and that is what is causing the vibration and noise. He made some calls and doesn't think the u joint is a repairable part, and that the whole shaft might need to be replaced. Anybody have any experience with this issue? Know of any solutions for parts? Thanks for your help!

He is mostly correct. For some absurd reason, BMW intentionally designed the u-joints so that they could NOT be replaced (easily). The standard u-joint "repair" procedure is to simply install a new or remanufactured driveshaft. Totally stupid design...

That said, you can actually rebuild them, but it takes a decent amount of work and may be more trouble than you're willing to pay a shop for. If you're paying a shop to perform the work, it's probably cheaper to just buy a reman'd driveshaft rather than paying them for custom fab work.

I had a drive shaft shop modify mine to make it serviceable. They cut and weld a serviceable end on the back of the drive-shaft. try that.

Perry

Originally Posted by commodorepdog

I had a drive shaft shop modify mine to make it serviceable. They cut and weld a serviceable end on the back of the drive-shaft. try that.

Perry

To me that sounds like a recipe for it being out of balance.

It can definitely be done, and is what I was alluding to above. Most driveshafts are serviceable, but apparently BMW (in their infinite wisdom) decided to make "lifetime" u-joints, just like they made "lifetime" diff fluid and "lifetime" trans fluid...

If/when my car needs new u-joints, I'm going to have it modified to be serviceable.

Originally Posted by jonesin

To me that sounds like a recipe for it being out of balance.

Joensin,

Normally I would agree but this would be a walk in a park for a good drive-line shop. The guys I go to make custom drive shafts for racecars and those crappy nascars. They make it right every time.

The other option is making a custom one piece driveshaft and saying goodbye to the center bearing.

Perry

Yeah, custom driveshafts are pretty common for special builds & swaps. No reason why an E36 driveshaft can't be modified to be serviceable.

Originally Posted by ZeGerman

Yeah, custom driveshafts are pretty common for special builds & swaps. No reason why an E36 driveshaft can't be modified to be serviceable.

Agreed! Modify!

I think for this person, it just depends on what costs the least amount of money.

Well - my mechanic found a used driveshaft for $150, and replaced it for me today. Vibration gone! Nice and smooth and quiet now.

HOWEVER... Now I have a Check Engine Light on right away at start up... I took it down to Advanced Auto to have them scan it and it came back with the following codes;

P1519
P0155
P0135
P1525
P0430

Now I am really concerned. Could these have been caused by the installation of the driveshaft??? The car is running smooth, maybe a little soft on the torque on the low end. Any ideas at all?

Did a bit of googling: P1519 and P1525 are, I believe, codes for the camshaft position sensor.

The other codes are for the O2 sensors/sensor heater. Probably won't have great fuel economy.

Don't freak out. Odds are you just need to replace some sensors which is a fairly simple job and isn't terribly expensive. I just purchased two pre-cat O2s for my M3 for 60 each.

I did some googling on this as well...

Is it possible that this was triggered by replacing the driveshaft? I know he had to remove the exhaust to access the shaft. The CE Light was not on before the repair of the driveshaft/ujoint.

What type of shop did you take it to? Dealership? Specialist?

Originally Posted by Skinfather

What type of shop did you take it to? Dealership? Specialist?

I took it to a certified mechanic that works out of his own garage. I have been taking my vehicles to him for years, and he has always been quick, convenient, and reliable. He has some experience with BMW's, so I felt comfortable with him doing the work.

He did tell me that at one point he had to disconnect something to do with the O2 sensors, and then he had to turn the key on and put the car in neutral for part of the procedure... he thought that might have triggered the fault codes.

I disconnected my battery last night to see if that would reset the codes, but it did not.

The engine won't run right with a camshaft code. Are you sure it's running properly?