OK, so I am not getting it - Pre-load center bearing

[Badkrma]

I have searched for additional information on pre-loading the center support bearing, and have not really come up with how to do it. can someone help me with this. I do not have the Bentley manuel, just a Chilton. Maybe if someone could scan the process out of the Bentley it would help me.

How long should this job take me on a 1990 535i automatic?

Thanks

Stephen

[Hector]

and it's a little tedious. Jack up the car as high as you can and put it on all fours. Disconnect the exhaust pipes, unclip the O2 sensor wire from the chasis clip, disconnect both rubber mounts near the tail pipe and set exhaust on a jack stand. Now that the entire exhaust is has been lowered, remove the heat shield. Space is tight but removal is doable. Unscrew both bolts holding center bearing and let it rest in its natural state. Then move the center bearing bracket toward the front of car about 1/4". I did mine about 3/8" but didn't want to push it too far--don't want to damage rubber membrane. (Note: the more you stretch the membrane, the more you preload the center bearing and the less it'll last.) I had reasons to do my the way I did. The installation is reverse of removal.

[Badkrma]

Hector,

Thank you for the reply, I am going to be putting a new one in as I believe from the noise it is making, it is bad. From one of the photos I saw, it didn't look like the holes lined when in the neutral state. I am sure it will make more sense once I take it apart.

Again, Thank you,

Stephen

[Jr ///M5]

You have to be aware that there are two steps to preloading the center bearing. The driveshaft must be perfectly centered in the tunnel, there are two small flats that you can measure from directly in front of the center bearing. Take all the slack out of the bolts on the center bearing, position the driveshaft in the center of the tunnel, then while you are holding the driveshaft centered, slide the center bearing forward about 1/4" and tighten the bolts.

There, now it's centered and pre-loaded!

Jr

[Jeff N.]

Noise? Typically the center bearing doesn't make noise. The rubber surround tends to fail over time and this leads to a vibration.

What sort of noise do you have?

[Badkrma]

There is a vibration sound coming from about the safety brake lever, from under the car at about 1500 RPM's .. It only happens on acceleration and only in the first two gears (automatic, hear it when it shifts into second if i am getting on it). I am going to be changing out the trans mounts and figured that if it has been doing this for very long (one year with me driving it and several with the other owner (one of the reasons that car was given to me)), then the center bearing most likely will need to be replaced. Your thoughts?

Stephen

[Jeff N.]

If you had a manual I'd suggest inspecting the guibo. Don't think you have one.

Well, with what you describe, you're in the right place. I'd think you'll want to take a close look at the tranny mounts. If they are shot, swap them and see what happens. That alone may fix your problem.

If they look OK, you may want to pull the driveline to inspect it. That of course is a PITA as you have to drop the exhaust and the heat shield to evan get a look at it. If you get that far - pulling it - it's easy to swap out the center bearing (swapping it can a PITA itself, but half the battle is getting the driveline out). You'll also want to carefully inspect all joints in the driveline including the aft CV joint and the u-joints. Any/all could be going.

Hope this helps.

Jeff



There is a vibration sound coming from about the safety brake lever, from under the car at about 1500 RPM's .. It only happens on acceleration and only in the first two gears (automatic, hear it when it shifts into second if i am getting on it). I am going to be changing out the trans mounts and figured that if it has been doing this for very long (one year with me driving it and several with the other owner (one of the reasons that car was given to me)), then the center bearing most likely will need to be replaced. Your thoughts?

Stephen