|07-25-2019, 10:36 AM||#1|
Join Date: Jun 2006
Location: Houston, Tx
My Ride: BMW
Powerflex rear differential bushing experience
I want to share my experience with a failing rear diff bushing and how changing it to powerflex definitely improved my car behavior.
I've had a good experience with powerflex products because since 2010 I got a set of FCABSs to replace the OEMs and since then I never had to replace that parts again or had any problem at all before that, replacing FCABS was a regular maintenance chore.
Like a lot of people here, I had the occasional famous "bump" presumably coming from the differential transfer case hitting the chassis when it suddenly changes from acceleration to engine brake resistance and then again to engine drive acceleration, like when going down on a hill and then accelerating, but also I had this strange behavior:
On hot days (like 100º) and the car stopped, when it started to move I could feel a rocking motion on the drivetrain, like if something was loose inside the differential and even worse, when idling in an uphill road and car moved forward, the rocking sensation became very noticeable.
Also, when the transmission was in Park and shifted to Drive, I could feel a movement, like something was leaning or loose in the rear suspension.
First thing was to check the rear diff bushing, it looked fine, no cracks, no damage, then I pulled out the differential and opened it looking for wear and excessive play between the pinion and crown. Everything looked normal.
Next was checking the rear subframe mounting points looking for damage, there was none. So I put new oil and sealed the lid back with the bmw recommended loctite gasket maker
so while I was waiting for the sealant I decided to remove the original bushing and replace it with the powerflex.
To remove the original bushing I got a loaned tool from Autozone: U joint service set tool (648617T), and from the local hardware store got a 1 foot threaded rod with some washers and a couple of nuts.
With all this hardware I could assemble an extractor tool using the 2 1/2 tube from the toolkit as the pushing tool and the 3" receiving tube on the other side and the threaded rod and nuts to do the job.
This way extracting the old bushing was easy and fast.
Then I mounted the new powerflex Bushing (part number: PFR5-4626), that was also much easier than installing a stock bushing and put everything back.
Finally, I took the car for a test drive and what a difference! now when shifting from Park to drive or reverse, I cannot feel any movement in the drivetrain it just shifts smoothly and when driving, cruising or engine braking I can feel that loose parts rocking vibration is totally gone.
My theory is that even if the bushing was not broken, in hot days or when the area around it was hot the rubber softened and lose tension and that was the reason I had all that movement in the diff.
Now, this bushing carries around 75% of differential weight and withstands all the torque and rocking motion coming from the driveshaft to it does a lot of work and when it fails you basically have a loose differential with all the negative consequences of that.
With the powerflex bushing, now my car feels like when it was new. I should have done this years ago.
Last edited by ralf; 07-25-2019 at 10:38 AM.
|07-28-2019, 03:44 AM||#2|
Join Date: Jul 2012
Location: Boca Raton, FL or Salisbury, NC
My Ride: 2001 325i Auto
Nice write up with pictures! First one I've seen using using a loaner tool.
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|07-28-2019, 05:29 AM||#3|
Join Date: Nov 2005
Location: Rochester, NY
My Ride: 2002 325iT
Thanks for the write-up! I've been debating switching the diff to polyurethane, and while I'm sure it would be great for autocross or the track, was concerned about noise while commuting on the highway. Your experience makes it sound like a good choice.
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