Wondering if anyone can help me find root cause for this rear axle failure...

[SilverBully]

Hi all,

I am writing to see if anyone can help me identify what went wrong and why my driver side axle failed, the car is a 2021 Toyota (pre June build date), its tuned with MHD Stage 2, has a 200 cell catted downpipe, charge pipe, MST V2 Intake, and the RSR lowering springs (mild drop 0.6-0.8") as well as some other misc parts such as the verus engineering heat shield.

As far as I know, the only mods that could impact axle durability are the tune (added power) and lowering springs (axle angle/sus geometry).
1. The lowering springs were installed by myself almost a year ago, since then there have been no noticeable clunks/noise/popping/etc from the rear axle
2. The MHD OTS tune is just not that powerful and afaik I believe these axles can hold way more power.

Timeline of the failure:

1. Sunday: Oil change, car wash, chill, no spirited driving afterwards, test drive and monitor oil level with bimmercode (Flash resistant takes a bit of driving to update)
2. Monday: Made an appointment for an alignment, new OEM tires wearing a bit uneven, car a bit too unsettled during hard braking led me to bring it in for alignment. Shop technician proceeded to drive my car in sport mode/manual shift right off the lift - while he didn't red line or launch the car, you can definitely hear him high revving the engine and driving it pretty hard for a test drive, I'll be dealing with that as a separate issue, this is only worth mentioning here since the failure happened very shortly after. I drove home in normal mode(10min drive) and discovered the test drive at that point.
3. Tuesday: Drove to work(25min drive) in normal mode since I am still waiting for the oil level measured to finish rising to the normal post-oil change level (97mm). Axle broke at my job's parking garage as I was going up the ramp to the third floor, at the base of the ramp there are these very small speed bumps which I drove over slowly as I usually do (no scrape or anything), the axle broke as I applied the throttle to start moving up the ramp.

I really just want to make sure I fix whatever issue could have caused this, I have ordered all one time used bolts, replacement axle and SPL Traction arms because they claim to reduce wheel hop (which I have felt in the past though not recently).

Also, any suggestions to help improve my drive train reliability here is welcomed, thank you all.

Broken axle:

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[lucky phil]

Hi all,

I am writing to see if anyone can help me identify what went wrong and why my driver side axle failed, the car is a 2021 Toyota (pre June build date), its tuned with MHD Stage 2, has a 200 cell catted downpipe, charge pipe, MST V2 Intake, and the RSR lowering springs (mild drop 0.6-0.8") as well as some other misc parts such as the verus engineering heat shield.

As far as I know, the only mods that could impact axle durability are the tune (added power) and lowering springs (axle angle/sus geometry).
1. The lowering springs were installed by myself almost a year ago, since then there have been no noticeable clunks/noise/popping/etc from the rear axle
2. The MHD OTS tune is just not that powerful and afaik I believe these axles can hold way more power.

Timeline of the failure:

1. Sunday: Oil change, car wash, chill, no spirited driving afterwards, test drive and monitor oil level with bimmercode (Flash resistant takes a bit of driving to update)
2. Monday: Made an appointment for an alignment, new OEM tires wearing a bit uneven, car a bit too unsettled during hard braking led me to bring it in for alignment. Shop technician proceeded to drive my car in sport mode/manual shift right off the lift - while he didn't red line or launch the car, you can definitely hear him high revving the engine and driving it pretty hard for a test drive, I'll be dealing with that as a separate issue, this is only worth mentioning here since the failure happened very shortly after. I drove home in normal mode(10min drive) and discovered the test drive at that point.
3. Tuesday: Drove to work(25min drive) in normal mode since I am still waiting for the oil level measured to finish rising to the normal post-oil change level (97mm). Axle broke at my job's parking garage as I was going up the ramp to the third floor, at the base of the ramp there are these very small speed bumps which I drove over slowly as I usually do (no scrape or anything), the axle broke as I applied the throttle to start moving up the ramp.

I really just want to make sure I fix whatever issue could have caused this, I have ordered all one time used bolts, replacement axle and SPL Traction arms because they claim to reduce wheel hop (which I have felt in the past though not recently).

Also, any suggestions to help improve my drive train reliability here is welcomed, thank you all.

Broken axle:

Not sufficient information. Mileage? Car use and type of driving you did pre failure? Do you "launch" the car regularly? Failures often aren't related to the immediate pre failure use. In other words you may have hurt it before the alignment and a spirited drive post alignment was the "straw".
I'd never let the alignment guy drive my car post alignment solo. I'd rather do that myself anyway. Too many clowns with no respect for a customers property work in automotive these days that don't know the difference between a test drive and a joy ride.
Phil

 

[SilverBully]

Not sufficient information. Mileage? Car use and type of driving you did pre failure? Do you "launch" the car regularly? Failures often aren't related to the immediate pre failure use. In other words you may have hurt it before the alignment and a spirited drive post alignment was the "straw".
I'd never let the alignment guy drive my car post alignment solo. I'd rather do that myself anyway. Too many clowns with no respect for a customers property work in automotive these days that don't know the difference between a test drive and a joy ride.
Phil

Thank you Phil,

~20,000 miles
Not daily driver, usually spirited driving with casual fun cruising.
I have launched a couple of times, some very short burnouts in there but nothing crazy and almost all that happened when the car was still new to me so over a year ago.

I'd never let the alignment guy drive my car post alignment solo

Lesson learned, believe me.

That being said, do you think I should replace both axles?

 

[lucky phil]

Thank you Phil,

~20,000 miles
Not daily driver, usually spirited driving with casual fun cruising.
I have launched a couple of times, some very short burnouts in there but nothing crazy and almost all that happened when the car was still new to me so over a year ago.



Lesson learned, believe me.

That being said, do you think I should replace both axles?

Honestly others will know this specific platform better with regards to axle reliability and your driving style but from what I can gather here the axles aren't a weak point for moderate power increases and spirited driving more for high HP applications. Things can also fail because they weren't 100% from manufacture as well. In other words "shit happens" so no I would only do the failed side but inspect the other as well as you can while you're there. If you looked at the bearing manufacturers life projections for a rolling element bearing you may be surprised at how short the projected life span is. Most exceed this easily but the occasional one doesn't.
Phil

 

[SilverBully]

Honestly others will know this specific platform better with regards to axle reliability and your driving style but from what I can gather here the axles aren't a weak point for moderate power increases and spirited driving more for high HP applications. Things can also fail because they weren't 100% from manufacture as well. In other words "shit happens" so no I would only do the failed side but inspect the other as well as you can while you're there. If you looked at the bearing manufacturers life projections for a rolling element bearing you may be surprised at how short the projected life span is. Most exceed this easily but the occasional one doesn't.
Phil

That is also what I am inclined to believe, this is just a freak failure with an extremely suspicious coincidence being so shortly after the alignment.

I inspected the "good axle" there is no weird up/down play, the shaft moves in-out freely, no binding, no leaking grease, boots are clean and look new.... in other words I see no visible indication I should be replacing it.

I really just needed to hear someone with more experience with this platform's opinion, I didn't want to miss something important here and may have ended up overthinking this over the weekend...

 

[itzTang]

Launchs and burnouts definitely gonna premature the life of the axle. But you’ll say people do burnouts more frequent and launch everyday and their axles are still fine. It’s just one of those things you pray doesn’t break on that burnout/launch lol

 

[licklobster]

MFR defect. The cages hardly see any load compared to the rest of the assembly. Balls are fine, as is the grease and star.

Wheel hop will destroy cages though, and you said you had it before. Could have cracked one without knowing it and finally had it let go.

TL : DR, impossible to isolate shattered cage, replace or upgrade and move on

 

[SilverBully]

Launchs and burnouts definitely gonna premature the life of the axle. But you’ll say people do burnouts more frequent and launch everyday and their axles are still fine. It’s just one of those things you pray doesn’t break on that burnout/launch lol

lol right, so many people abuse their cars and never break an axle, I’m just one of the lucky ones I guess

 

[SilverBully]

MFR defect. The cages hardly see any load compared to the rest of the assembly. Balls are fine, as is the grease and star.

Wheel hop will destroy cages though, and you said you had it before. Could have cracked one without knowing it and finally had it let go.

TL : DR, impossible to isolate shattered cage, replace or upgrade and move on

Thank you, yeah I have had some wheel hop unfortunately, I always let off and don’t stay on it when it happens but its has happened.

What would you say is the most cost effective way to reduce/eliminate wheel hop? I already ordered the traction arms from SPL but wondering if there are other things that can help

 

[jmikes]

It's worth noting that the stock axles are known to fail off just an ethanol tune.

While this typically only happens when hooking good on a hard launch, it's possible that during more spirited drives / launches the axle became cracked/weakened over time, and the load put on it from driving up an incline was enough to break it.

Just a theory to keep in mind.

 

[exe36m3]

Coming from the BMW side, I've been on the forums for near 25 years, broken axles aren't a common thread. I'd even say rare because at best I remember maybe seeing something once tops. So personally, I'd chalk this up to defect from manufacturing and nothing you or a tech did.

 

[SilverBully]

the axle became cracked/weakened over time, and the load put on it from driving up an incline was enough to break it.

Would you replace both axles? if one was weakened over time its likely the other one isn't in good shape either

So personally, I'd chalk this up to defect from manufacturing and nothing you or a tech did.

I agree, he is still a POS for joy riding my car though... however, I am inclined to believe this is the right answer, it was just a shit axle and I need to move on, but I guess we won't really know until the other side blows up next (or doesn't) - wish me luck!

 

[itzTang]

Would you replace both axles? if one was weakened over time its likely the other one isn't in good shape either



I agree, he is still a POS for joy riding my car though... however, I am inclined to believe this is the right answer, it was just a shit axle and I need to move on, but I guess we won't really know until the other side blows up next (or doesn't) - wish me luck!

Just the one that had issue. No need to replace something that isn’t broken.

 

[SilverBully]

So I have an update/question.... I ordered part number 42340-WAA04 from Toyota parts online and received a different looking part. I was wondering if anyone here can help me validate the part number? I entered the car VIN and it is supposed to be correct according to the website but I am now doubting that after comparing both parts.

Edit: Attaching a picture just not working right now :/

 

[SilverBully]

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