[ZPD]

I am posting this to help the next guy.

Several weeks ago I was at Circuit of the Americas. It was around 100 degrees and I am sure track temps were even hotter. I pushed hard for several laps on Day 2 of a 2-day event and got black-flagged. The pit worker told me that corner workers observed I had smoke coming out when I was hard braking before turn 11 and accelerating out of a few of the corners. I ruled out brake dust and headed home fearing that there was something catastrophic even though there were no errors on the dash or codes.
When I got home and put my car on the lift I saw that the driver's side inner CV boot was ripped and grease was all over the exhaust. There was some oil splashed around out of the diff vent as well. After some googling I found that you can't buy just the CV boot and you have to buy an entire axle. I also stumbled across a note that said that if a customer has a boot failure due to hard driving then replace the axle shaft with an axle meant for the M3/4 CS/CSL because the boot can withstand a higher temperature.
The dealership wouldn't warranty the repair since I modified my suspension but Bimmerworld gave me a good deal on a pair of CSL Axles. The swap wasn't very hard and could probably be done in 2 hours if you have aftermarket exhaust.

For anyone encountering the same problem down the road the part numbers for the axles are:
Left: 33207887199
Right: 33207887200

And here is a video I made of doing the swap:

[Reesnat]

Thank you for sharing your experience. Sorry for your troubles but hopefully you have a stronger and more capable car now!

[TallGibbs]

Just to confirm, which car model and year did you have to do this swap on?

[ZPD]

Originally Posted by TallGibbs

Just to confirm, which car model and year did you have to do this swap on?

It is on my 2023 G87.

The CS/ CSL axles fit G87, G80, and G82

[TallGibbs]

Originally Posted by ZPD

It is on my 2023 G87.

The CS/ CSL axles fit G87, G80, and G82

Ok good to know. First time I had read about these parts being shared across platforms so good to know for future track stressing.

[LeggoRacing]

Thanks for sharing and learning for the community. Looks like a fun swap

[ZPD]

Originally Posted by LeggoRacing

Thanks for sharing and learning for the community. Looks like a fun swap

I feel like I have been the guinea pig for far too many things

[gnx]

This is a known issue with the g8X platform. It was mentioned by Mischa Charoudin in a video as one of the reasons why the APEX G80 M3 Nurburgring taxi car was sold.

[Ojala]

Differential heat management is an issue that is fairly common with other platforms. Lots of cars need heat exchangers for the diff which would explain oil from the diff vent. I'm curious about the torn boot. Is the cause the exhaust, the diff, or something else?

[clutchdj]

sheesh that is not supposed to happen. At thunderbolt last month it felt like my left hub bearing was about to take a dump right before turn 9 but now that I think about it, maybe the left axle bearing was stressing out. heat index was over 100F. I had to change out hub bearings at 4k on the f87 but axles should not fail. thanks for sharing OP.

[DutchBoysRacing]

Originally Posted by ZPD

I am posting this to help the next guy.

Several weeks ago I was at Circuit of the Americas. It was around 100 degrees and I am sure track temps were even hotter. I pushed hard for several laps on Day 2 of a 2-day event and got black-flagged. The pit worker told me that corner workers observed I had smoke coming out when I was hard braking before turn 11 and accelerating out of a few of the corners. I ruled out brake dust and headed home fearing that there was something catastrophic even though there were no errors on the dash or codes.
When I got home and put my car on the lift I saw that the driver's side inner CV boot was ripped and grease was all over the exhaust. There was some oil splashed around out of the diff vent as well. After some googling I found that you can't buy just the CV boot and you have to buy an entire axle. I also stumbled across a note that said that if a customer has a boot failure due to hard driving then replace the axle shaft with an axle meant for the M3/4 CS/CSL because the boot can withstand a higher temperature.
The dealership wouldn't warranty the repair since I modified my suspension but Bimmerworld gave me a good deal on a pair of CSL Axles. The swap wasn't very hard and could probably be done in 2 hours if you have aftermarket exhaust.

For anyone encountering the same problem down the road the part numbers for the axles are:
Left: 33207887199
Right: 33207887200

And here is a video I made of doing the swap:

Interesting, keep us updated on this. I track a lot (monthly) in SoCal and usually keep it mellow in the summer but if this is a common issue I'd like to address it ahead of time.

[GenXG87]

Dang. I was just checking the prices on those. So crazy no one offers a boot replacement kit.

Thanks for sharing the video.

[ZPD]

Originally Posted by DutchBoysRacing

Interesting, keep us updated on this. I track a lot (monthly) in SoCal and usually keep it mellow in the summer but if this is a common issue I'd like to address it ahead of time.

I had a track day this weekend at Eagles Canyon Raceway and it was over 105 degrees. It's not as abusive COTA but still pretty harsh conditions. I checked my axles tonight and there is no sign of wear on the boots. So that is good news.

[ZPD]

So I decided to take apart the axle today. It came apart really easily. I might try to find a neoprene or viton boot that fits to satisfy my curiosity.