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5 Series DIY
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  #1  
Old 05-10-2015, 07:58 AM
kayaktak kayaktak is offline
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Location: Vietnam
 
Join Date: May 2015
Posts: 4
Mein Auto: E34 520I M50B20 BC42665
DIY: Driveshaft Flex Disc & Center Support Bearing (E34 520i/525i)

Hi,

Though there are a number of very detailed guides on giubo and drive shaft bearing replacement, I would like to share my experience replacing these worn out parts on the drive shaft of my E34. Both the giubo and center support bearing were replaced without detaching the exhaust or drive shaft.

The main contribution of this post would be the (1) tips and shortcuts, (2) points to take note off, (3) how to do it alone without a hoist or lift, or proper tools (i.e. ghetto style) & (4) lots of pictures.

This DIY procedure applies to the BMW E34 520i & 525i.

Time needed:
  • 4 to 8 hours (1st time)
  • 2 to 3 hours (with practice)
  • 1.5 to 2 hours (with hoist and complete set of tools).
The main steps can be summarised as follow (detailed DIY after summary):
Step 1 - Raise car off the ground
Step 2 - Loosen exhaust
Step 3 - Remove heat shield
Step 4 - Unbolt giubo transmission flange nuts
Step 5 - Unbolt CSB, unbolt structural reinforcement
Step 6 - Mark drive shaft, disconnect giubo and slide out front drive shaft
Step 7 - Remove CSB
Step 8 - Remove giubo from drive shaft, remove drive shaft clamp, *remove centering sleeve
Step 9 - Clean splines of drive shaft
Step 10 - Install new CSB, *install new dust cover
Step 11 - Install new giubo to drive shaft, install new clamp with bushing, install new centering sleeve
Step 12 - Grease drive shaft spline, reconnect drive shaft
Step 13 - Attach giubo to transmission flange
Step 14 - Preload and tighten CSB, reinstall structural reinforcement
Step 15 - Reinstall heat shield
Step 16 - Reinstall exhaust
Step 17 - Lower car, test drive

_a2_
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  #2  
Old 05-16-2015, 10:03 PM
kayaktak kayaktak is offline
Registered User
Location: Vietnam
 
Join Date: May 2015
Posts: 4
Mein Auto: E34 520I M50B20 BC42665
Background

Symptoms:
  • Car shakes violently at 3k-4k rpm, at any gear
  • Knock or delay when shifting from drive to reverse, or from reverse to drive
  • Vibration or knocks from the centerline of the car (drive shaft area)

Initially, I thought the vibrations were RPM-linked. The car would shake violently during hard accelerations, while feel relatively smooth even during high speed, low RPM drives. Upon further reading up online, it seems that the shaking was not RPM-linked. Instead, I suspect the torque from the engine peaks in the 3-4k RPM range. This means that the torque transfer was highest inside this RPM range, which probably puts the most strain on the damaged flex disc (giubo) and torn rubber housing for the center support bearing (CSB).

A visit to a trusted BMW specialist confirmed the drive shaft issue. However, he readily diagnosed that a total replacement for the drive shaft (a.k.a. propeller shaft) was needed with only visual checks using a mirror, when the car is up on a hoist. The drive shaft was not physically inspected by hand. No spare drive shaft was available from the scrapyard at that time, so I did not leave the vehicle with the mechanic.

A full drive shaft replacement job, including a "new" drive shaft from the scrapyard, would cost a thousand over dollars. I did not want to part with the money so quickly, so I thought of giving the drive shaft a rebuild if necessary. Turns out, the drive shaft is not easily rebuildable, but many wear and tear parts can be replaced if the drive shaft is still functioning well. I decided to do a more in depth diagnosis by removing the drive shaft / exhaust heat shield. Luckily, after removing the heat shield, I was able to check the drive shaft and it seems that the joints are all nice and tight. So off I went to the parts supplier for some parts to refresh the drive shaft of my mum's E34.

I was not aware of that the centering sleeve could be replaced, so I did not ask for that part. Given a choice, I would have liked to replace it as well, but the cracked sleeve in the drive shaft seem to be holding up after replacing the flex disc and CSB.

In fact, about 6000km ago and before a 1500km road trip, I noticed kevlar reinforcement fraying out from the flex disc. Back then, I did not know that this means that the flex disc is already badly worn. When replacing the flex disc, I also found out that a mechanic from another workshop had installed the flex disc incorrectly. The dust covers for the CSB was also not installed properly. The drive shaft clamp was also missing a toothed sleeve. All these issues were resolved when I reinstalled the wear and tear parts.

With the background story out of the way, let's get started with the detailed DIY on "How to replace your Flexible Disc Connector (Giubo) and Center Support with Bearing (CSB) for your E34 drive shaft".

Last edited by kayaktak; 05-17-2015 at 04:34 AM.
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  #3  
Old 05-16-2015, 10:18 PM
kayaktak kayaktak is offline
Registered User
Location: Vietnam
 
Join Date: May 2015
Posts: 4
Mein Auto: E34 520I M50B20 BC42665
Parts needed:
#2 - Flex Disc - Lemforder 26111225624 (US$26)
#9 & #10 - Dust Cover Plates - BMW OEM 26111226553 & 26111226552 (US$27)
#6 - Driveshaft Center Support (with bearings) - febi 26121226723 (US$26.50)
#12 - Threaded clamp ring with toothed washer - BMW OEM 26117514037 (US$13.60)
#5 - M10 self locking hex nut x 6 (16mm hex) - BMW OEM 07129964672 (US$8)
#1 - Driveshaft centering sleeve - 26117526611 (did not buy this part)

Prices shown are local prices converted to US dollars. Can you imagine my disbelief when the two tiny pieces of dust covers cost more than the flex disc or the whole center bearing unit?

Source: http://www.realoem.com/bmw/enUS/show...diagId=26_0072

Personal Protective Equipment
Hands - Latex/Nitrile gloves
Lungs - N95 mask
Eyes - Safety goggles
Arms & legs - long sleeve garment
Hair - Cap / plastic bag

Tools needed:
A - 13mm open wrench
B - 16mm open wrench
C - 17mm open wrench
D - 16/17mm 6 point socket wrench
E - Socket wrench with 13/16/17mm hex sockets
F - Socket extension (short)
G - Wife's nail varnish
H - Circlip pliers
I - Bearings removal tool (durable flathead screwdriver)
J - Bearings removal tool (solid hammer)
K - Driveshaft cleaning tool (something hard and pointed)
L - Driveshaft cleaning tool (stiff bristle brush)
M - Bearing installation tool (wooden mallet with rubber handle)
N - Penetrating lubricant
O - Transmission/Exhaust hoist

Not shown - hydraulic car jack, jack stands, ramps.

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  #4  
Old 05-17-2015, 08:49 AM
kayaktak kayaktak is offline
Registered User
Location: Vietnam
 
Join Date: May 2015
Posts: 4
Mein Auto: E34 520I M50B20 BC42665
If I have two hours to fell a tree, I would spend the first sharpening my axe

SECTION 1: DIAGNOSIS
It is important to make sure we are fixing the right problem. Unless we have infinite resources or want to completely rebuild the car, we would want to make sure our time, effort and money are only used when necessary.

Just like a doctor who prescribes medicine after a 2 minute diagnosis, you should be wary if the mechanic immediately recommends part replacement after a 2 minute diagnosis. Effort spent on a proper diagnosis will eventually save time and money during part replacement.

For a rear wheel drive BMW, the drive shaft runs along the centerline of our car. We have to access the drive shaft in order to assess its condition. Looking up from the bottom of the car, the drive shaft is located above the exhaust pipes, protected by a stiff, but malleable, aluminum heat shield. In order to inspect the CSB and check the drive shaft for play, we need to remove this heat shield. The transmission to drive shaft connection (flex disc) and the drive shaft to rear differential connection can be inspected visually once the car is off the ground without having to remove the heat shield.

Step 1a: Raise car
Get the car raised by any method of your choice. It is important to make sure at least one of the rear wheel is off the ground. The allows the rear wheel to spin, which means that the drive shaft can be turned as well.

I used ramps for the front wheels and jacks for the rear subframe. This got the car off the ground, but the job would definitely be easier with more room beneath the car.


If your jack does not go high enough to raise the rear wheel off the ground, you can place some wooden planks on the jack to give it a bit more maximum height. The wood may compress, so make sure the wood is tough enough to withstand the weight of the car.


Double check that the car is securely raised by nudging the car using your body weight. Whatever method you choose to get the car off the ground, please make sure you do not rely solely on hydraulic jacks to keep the car raised. Hydraulic jacks will fail unexpectedly and are not designed to hold a car up in the air.

Step 1b: Take a break
This step is very important. Take a break. The exhaust pipes are probably still hot if you drove the car. Use this time to prepare your tools, grab a drink from the fridge, or just have a stretch. Make sure the exhaust pipes are cool before doing any work underneath the car.

Step 2a: Inspect flex disc
The flex disc is the connection between the transmission output flange and the front drive shaft flange.

With the car off the ground, get under the car and take a look at the flex disc located just behind the transmission. You can probably continue driving if the flex disc only shows cracks in the rubber, but if you can see the kevlar threads, it's definitely time to replace the flex disc. Mine looks like this even before the road trip, and before the car shook violently between 3k-4k RPM.



I managed to do a 1600km two day road trip, traveling mostly at 130km/h and up to 170km/h, even with the flex disc in this condition. The heft of the E34 with the comfort 15inch tyres probably made the ride feel more stable than the speed would suggest. Often, apart from the wind noise, it feels no different travelling at 50km/h and at 150km/h. I did not feel anything unusual during the drive, both as a driver and as a passenger, but I would not recommend pushing your luck the way I did.

Upon closer inspection, we can see that the flex disc was installed wrongly. There's only a 50% chance of installing it wrongly if the installer does not pay attention to the arrows. The nuts and bolts are also wrongly attached to the drive shaft flange. The nut should be on the same side as the flange, and tightened by torquing on the nut.


In this case, the transmission flange pulled and tore the rubber reinforcement away from the drive shaft flange, instead of pushing into the rubber reinforcement towards the drive shaft flange during forward movements.


Step 2b: Inspect rear drive shaft to differential connection
At this moment, we can also take a quick look at the rear differential area. The connection between the drive shaft and the rear differential looks like this for the E34 520i. The nuts and bolts look ok, the flanges look fine too. No flex disc at the rear, so there is nothing much to check here for now.


Step 2c: Inspect transmission mounts
While not essential to the drive shaft DIY, you may want to inspect the transmission mounts while you are doing this job. The transmission mount are very accessible during this job and it would be a good idea to replace the transmission mounts if they are overly compressed or if the rubber is damaged. The mounts come in a pair and are located just beneath the flex disc. I removed the rear transmission support bracket, but it is not an essential step to completing the flex disc and CSB DIY.


There seem to be two types of transmission mounts for my 4 speed automatic transmission. The diagonal rubber mount seems to be the original version and is made of softer rubber. I decided to try out the Lemforder cylindrical transmission mounts just to see if there is a difference in NVH isolation. Results after 1000km: Vibrations are more obvious, especially during idle. I'm not sure if it is because the engine mounts were over compressed when the transmission was slightly lowered during the flex disc and CSB job. For now, I would attribute the vibrations to the firmer transmission mounts, which does not seem to benefit an automatic transmission car since there is no flywheel to match with the engine.


Step 3a: Lower exhaust
The Bentley manual, the Pelican Parts technical article and the DIYs that I can find all call for the removal of the exhaust pipes. In the 520i/525i where the exhaust system is simpler, I decided to lower the exhaust instead of removing it completely. I am not sure if this will damage your exhaust system, do please do so at your own risk. If you are worried about damaging your exhaust systems, please remove the exhaust pipes completely. There did not seem to be any adverse effects by simply lowering the exhaust system slightly, so I continued with this method. In fact, leaving the exhaust system intact has another advantage which you will discover later on in this DIY.

To lower the exhaust, we need to remove the exhaust mounts at 3 locations. For my car, all the mounts can be removed with a 13mm wrench. Prepare two supports in advance. I used empty engine oil containers.

First, remove the bracket holding the rubber suspension, just after the mid silencer. Next, remove the two nuts and bolts that are secured to the rear end of the transmission. Lastly, remove the 2 nuts holding up the rear silencer at the rear bumper.


Support the now unsuspended exhaust system using your supports. This ensures that the connection to the exhaust headers are not strained excessively.

Source: http://www.realoem.com/bmw/enUS/show...diagId=18_0172 & http://www.realoem.com/bmw/enUS/show...diagId=18_0158, http://www.pelicanparts.com/BMW/tech.../E36-Guibo.htm


Step 3b: Remove heat shield
With the exhaust slightly lowered and supported, proceed to remove the heat shield. There would definitely be more space to remove the heat shield if the exhaust pipes are out of the way, but this space is sufficient for us to work with. This is what the lowered exhaust system looks like.


The heat shield is held in place by 4 bolts. Remove the bolts using the same 13mm wrench. Some areas might be a too cramp for a socket wrench, so just use a regular wrench to reach the bolts. The heat shield on your car may be secured with more or less bolts, so just check on the heat shield itself when you are removing it. This process is very straight forward so I did not document the heat shield removal process. If the heat shield is stuck because there is not enough ground clearance to slide the heat shield out, gently fold the heat shield and wriggle it out of the space between the exhaust pipes and the drive shaft.

You should be able to remove the heat shield without much difficulty.


Step 4a: Inspect CSB & drive shaft
With the exhaust and heat shield out of the way, you can now inspect the CSB & drive shaft.

Take a look at the CSB. It should be held in place by 2 bolts. The rubber housing for my CSB is clearly torn. We will get to see how badly torn the rubber housing is later, when we remove the two bolts holding it in place. Also, this is a good time to mark the alignment of the drive shaft. My wife brought my golden permanent market to work, so I borrowed her nail varnish for this task. Most guides will tell you to mark on the drive shaft itself, but for perfect alignment, I found it more accurate to mark directly on the spline.


With the transmission in Park (or in gear for manual cars), and the handbrake disengaged, try to rotate the drive shaft with your hands. The drive shaft should be held in place by the transmission. If it rotates slightly, have a look at the flex disc. The rubber should be firm enough to prevent any significant rotation by hand. If the drive shaft rotates, the flex disc should be replaced.

Next, engage the handbrake firmly. This locks the wheels in place, which should lock the drive shaft too. Rock the drive shaft up and down, side to side. If it moves, look for the loose areas in the drive shaft. The two U-joints should not have any play in them. If it rattles in any way, chances are you need to get the joints serviced by a professional. Alternatively, it may be cheaper and more convenient to get a refurbished drive shaft. From what I have read, the U-joints are not designed to be easily serviced even by regular car mechanics.

To further inspect the CSB, remove the 2 bolts that are holding it in place. In this picture, the two bolts have been moved to an adjacent hole towards the rear of the car. As you can see, the rubber housing is totally torn. Essentially, there is no support given to the bearing. This probably explains the violent shakes when the car is pushed to max torque at 3k-4k RPM. Luckily, there is no play at the U-joints, so the drive shaft can probably be reused if the splines are still in good working order.


This sums up our diagnosis section. From our detailed diagnosis, we can conclude that the flex disc and CSB need to be replaced. The drive shaft splines look OK, but we would have to remove the front part of the drive shaft to be completely sure. The joints seem to be holding up well, so let's hope the drive shaft can be reused after replacing the wear and tear parts.

Time taken so far: 1-2 hours
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