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2010 2011 BMW 5 Series Forum F10 F10 Technical Topics DIY Guides & Discussions DIY X-Drive thrust arm / tension strut / traction strut / trailing arm replacement
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      12-16-2023, 05:55 AM   #1
Surly73
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DIY X-Drive thrust arm / tension strut / traction strut / trailing arm replacement

My searches of thread titles did not reveal another thread here about this so I started one. This is not a complete write up, but links to materials I used to prepare for this job, and any additional tips, tricks or corrections I would make to what's already out there.

This is the work required for the VERY common thrust arm bushing failure. In my case I elected to replace the entires arms with replacement arms with Turner monoballs already pressed into place.

For this job, the X-Drive is a different procedure and, frankly, substantially more fiddly and difficult. Of note for X-Drive compared to RWD:
  • BMW says you CANNOT use an impact tool on the ball joint at the knuckle
  • The driveshafts must be disconnected at the wheels to remove the ball joint end of the arm
  • Some fasteners have different heads
  • Different part numbers for arms and bushings

Videos and writeups of this job on the X-Drive are rare compared to RWD. I have to tip my hat. I don't usually find one video that covers everything but in this case this guy covers it really well, including part numbers and torques.

Any additional comments I have are below:


1/ I released the torque on the collar bolt (center of the wheel) before raising the car on both sides. Final torque was done with the car back on the ground (both sides).



2/ This video does not warn of the special circumstances at the knuckle (which in this case on the X-Drive BMW calls the "swivel bearing"). BMW specifically says that impact tools are not to be used and that if the "steel bushing" spins you must replace the swivel bushing (e.g. the entire knuckle). This is a big deal!

I don't find any pictures or other language clarifying what this means. In this case I believe it means that if the ball joint spins, which is usually not a huge deal, the knuckle is toast because the mating surface will spin and damage the machining. I don't know if the ball joint has any sensitivity to spinning itself. I noticed that if it turned with hand tools the rubber boot puckered instead of just letting the joint spin like I usually encounter.

The video shows the usual T50 counter hold with a ratchet against a 24mm combination wrench and the two workers just wailing away on both. Based on BMW's warnings, I advise against it out of caution - strictly counterhold the T50 without turning it, at least until the ball joint is well separated from the knuckle/swivel bearing.

Unfastening this fastener was the most grueling on my car. I broke the torque with my largest breaker bar, then did the counter hold and combo wrench work. As it unbolted in some places it got harder as 12-13 years of corrosion was encountered etc... Of course by that time the nut was significantly unthreaded and the counter hold wobbled all over the place.

A ratcheting, box end 24mm wrench would make this substantially easier. I would recommend a good one with a swivel end as well. However, early in the process a ratcheting version might not withstand the torque required. So, if you have the budget, get both. For the standard combo wrench - longer is better.


3/ BMW also says that the swivel bearing (knuckle) surfaces should be clean and free of oil and dirt. With the thrust arm removed I cleaned it all up with brake cleaner and clean towels.



4/ The mechanics in the video jack up a wheel to "normal position" to torque both ends. This isn't necessary in this way. First, if you have the traditional rubber bushing, the bushing end needs to be in normal position. If you have a poly or monoball, it isn't necessary at all.

BMW gives you a shortcut - they tell you to torque the bushing end first and advise that "normal position" is achieved if you have the end of the ball joint 2cm above the swivel bearing/knuckle with the suspension at full extension. IMO this is easier and safer.

It is not necessary to torque the ball joint at normal position at all. IMO it is safer to leave the suspension at extension with a helper counter-holding the steering wheel.



5/ Replacement of all nuts and bolts is required by BMW because all of these fasteners are torque-to-yield. Lots of people don't bother. I always have. ECS sells it all. Some of these torques are high - have large breaker bars and eat your Wheaties.



6/ unless I did it wrong, the proper tooth engagement of the driveshaft on assembly is absolutely critical, but pretty straightforward for anyone with any mechanical understanding. You need to properly mate the teeth - simple as that. Assemble with hand tools, nudging the drive shaft and the rotor as you feel the teeth seat and engage.


I think that's it. The video I linked is quite complete which I appreciated.
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      01-06-2024, 10:53 AM   #2
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Quote:
6/ unless I did it wrong, the proper tooth engagement of the driveshaft on assembly is absolutely critical, but pretty straightforward for anyone with any mechanical understanding. You need to properly mate the teeth - simple as that. Assemble with hand tools, nudging the drive shaft and the rotor as you feel the teeth seat and engage.

TIS makes it sound like mating the teeth will be very difficult. For sure you should be careful here but the warnings in TIS made me over think this I checked it like 20 times. It should gently slide in... don't use brute force and don't over think it.
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      01-06-2024, 11:17 AM   #3
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Quote:
Originally Posted by bk_mike View Post
TIS makes it sound like mating the teeth will be very difficult. For sure you should be careful here but the warnings in TIS made me over think this I checked it like 20 times. It should gently slide in... don't use brute force and don't over think it.
Yea don't overthink it. Just push it in, wiggle and rotate it a little to ensure proper tooth engagement, and then hold it tight while you put the bolt on.
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