[FaRKle!]

So this weekend I was at the track testing out a new suspension config. Saturday was dry, and even with r-comps I found I could easily get the rear end loose while trail braking and had to be ULTRA smooth in its release to maintain composure. I attributed this to having too stiff of a rear sway bar (currently running 17mm KC Design).

Saturday night it rained heavily and Sunday for the first half of the day there was a lot of standing water on the track (and a bunch of people spun). Knowing these conditions and how much I had to pay attention to the rear end the day before in the dry, I decided to disconnect my rear sway bar on one side. During my sessions the car felt good and rear end grip was much better and easier to manage. Sure, I had more rear body roll, but I could be quicker off the brake without upsetting the rear. Even after things dried up in the afternoon it was an improvement. It was absolutely the right thing to do for the wet track conditions.

Unfortunately at the end of the day I discovered why you shouldn't disconnect the rear sway bar on the F2x/F3x/F8x cars... When the rear sway bar is disconnected, the rear axle half shaft boot can travel high enough to contact the sway bar. While I was changing my track pads and wheels out back for street I noticed a bunch of black grease all over my damper on the side I disconnected the bar from and saw that the bar had ripped the boot open.



To make matters worse, there isn't a way to replace those boots as they don't have their own PN and there aren't aftermarket replacement kits, so I'm going to have to replace the whole half shaft. I'm a big DIYer, but I don't have the specialized tools and presses to remove the rear half shafts from the hub, so it looks like I'm going to be paying for this one... At least used half shafts aren't terribly pricey (~$100). Oops.

I should probably add a disclaimer that just because the 17mm KC Design sway bar is too stiff for my setup, doesn't mean it's too stiff for others. I'm running pretty high rear spring rates (900lbs/in, same as Ohlins R&T), and I haven't seen any other aftermarket kit go that high. Furthermore, if I had an LSD, then it probably would've been fine.

[Billfitz]

I found this:
https://www.autozone.com/drivetrain/.../695068_0_3550

[FaRKle!]

Originally Posted by Billfitz

I found this:
https://www.autozone.com/drivetrain/.../695068_0_3550

Unfortunately that's for the front axle half shafts, where the boot does have a PN and there's a BMW procedure for replacing it. Thanks though.

[zole2112]

I think the front outer on my xdrive are the same as the rear outer, this https://www.fcpeuro.com/products/bmw...kn-31607549468
If you measure the diameter at the CV Joint and the axle diameter as well as the boot length I will measure the same on my outer boot on the axle sitting on my bedroom floor.

[Polo08816]

Originally Posted by FaRKle!

So this weekend I was at the track testing out a new suspension config. Saturday was dry, and even with r-comps I found I could easily get the rear end loose while trail braking and had to be ULTRA smooth in its release to maintain composure. I attributed this to having too stiff of a rear sway bar (currently running 17mm KC Design).

Saturday night it rained heavily and Sunday for the first half of the day there was a lot of standing water on the track (and a bunch of people spun). Knowing these conditions and how much I had to pay attention to the rear end the day before in the dry, I decided to disconnect my rear sway bar on one side. During my sessions the car felt good and rear end grip was much better and easier to manage. Sure, I had more rear body roll, but I could be quicker off the brake without upsetting the rear. Even after things dried up in the afternoon it was an improvement. It was absolutely the right thing to do for the wet track conditions.

Unfortunately at the end of the day I discovered why you shouldn't disconnect the rear sway bar on the F2x/F3x/F8x cars... When the rear sway bar is disconnected, the rear axle half shaft boot can travel high enough to contact the sway bar. While I was changing my track pads and wheels out back for street I noticed a bunch of black grease all over my damper on the side I disconnected the bar from and saw that the bar had ripped the boot open.



To make matters worse, there isn't a way to replace those boots as they don't have their own PN and there aren't aftermarket replacement kits, so I'm going to have to replace the whole half shaft. I'm a big DIYer, but I don't have the specialized tools and presses to remove the rear half shafts from the hub, so it looks like I'm going to be paying for this one... At least used half shafts aren't terribly pricey (~$100). Oops.

I should probably add a disclaimer that just because the 17mm KC Design sway bar is too stiff for my setup, doesn't mean it's too stiff for others. I'm running pretty high rear spring rates (900lbs/in, same as Ohlins R&T), and I haven't seen any other aftermarket kit go that high. Furthermore, if I had an LSD, then it probably would've been fine.

Are you looking to remove the half shafts from the hub AND differential?

[Billfitz]

A split CV boot doesn't require pulling the drive shaft.
https://shop.advanceautoparts.com/p/...E&gclsrc=aw.ds

I can't say if anyone makes one that will fit the OP's car.

[andino]

Originally Posted by Billfitz

A split CV boot doesn't require pulling the drive shaft.
https://shop.advanceautoparts.com/p/...E&gclsrc=aw.ds

I can't say if anyone makes one that will fit the OP's car.

The split boots are just a temporary solution. I ran one when I tore my front CV boot and needed to pack the bearings until I could get them fixed.

[FaRKle!]

Originally Posted by Polo08816

Are you looking to remove the half shafts from the hub AND differential?

Yup, because the BMW procedure says you need to take the shaft out of the diff in order to have enough room to push it out of the hub.

With the amount of work it is to replace a half shaft, I'm seriously thinking of just spending the $ and seeing what kind of LSD options I have since I'll be paying for most of that labor anyways... lol

[Jvac]

Originally Posted by FaRKle!

Yup, because the BMW procedure says you need to take the shaft out of the diff in order to have enough room to push it out of the hub.

With the amount of work it is to replace a half shaft, I'm seriously thinking of just spending the $ and seeing what kind of LSD options I have since I'll be paying for most of that labor anyways... lol

That's a bummer but thanks for putting the story here for the benefit of others.
If you're looking at aftermarket lsd options, perhaps you'd be interested in my oe 'pumpkin' /open diff housing? I think quaife and some other shops can build you a diff if you provide a donor housing. It's been sitting in my garage since I had the m performance differential installed last spring. It's rwd auto, but I believe it is also compatible on xDrive auto cars. You've done a lot for this forum community so I'll give you a good deal on it.

[johnung]

Originally Posted by FaRKle!

Yup, because the BMW procedure says you need to take the shaft out of the diff in order to have enough room to push it out of the hub.

With the amount of work it is to replace a half shaft, I'm seriously thinking of just spending the $ and seeing what kind of LSD options I have since I'll be paying for most of that labor anyways... lol

That really sucks! Sometimes a solution can be found in the basic mechanic's toolkit.

[Polo08816]

Originally Posted by johnung

That really sucks! Sometimes a solution can be found in the basic mechanic's toolkit.

The drinks on the right might get you sick.

[FaRKle!]

Originally Posted by Jvac

That's a bummer but thanks for putting the story here for the benefit of others.
If you're looking at aftermarket lsd options, perhaps you'd be interested in my oe 'pumpkin' /open diff housing? I think quaife and some other shops can build you a diff if you provide a donor housing. It's been sitting in my garage since I had the m performance differential installed last spring. It's rwd auto, but I believe it is also compatible on xDrive auto cars. You've done a lot for this forum community so I'll give you a good deal on it.

Thanks for the offer. Unfortunately my diff is different from the one that came on the 335i. 2.81 gearing vs 3.23, and the half-shaft seals are 66mm instead of 72mm.

Other vehicles that share the same diff as the 328dx are the 2/3/430i AT, and and 2/3/440ix AT.

[Jvac]

Originally Posted by FaRKle!

Thanks for the offer. Unfortunately my diff is different from the one that came on the 335i. 2.81 gearing vs 3.23, and the half-shaft seals are 66mm instead of 72mm.

Other vehicles that share the same diff as the 328dx are the 2/3/430i AT, and and 2/3/440ix AT.

Shucks!