Stripped drive shaft threads, experienced opinions sought

[Jack]

Thank you for accepting me to the forum,

I got my car back from a local dealer telling me that the drive shaft threads stripped while removing the nut. The car was in for a bearing replacement and they informed me the nut became tight when trying to remove it. The mechanic didn’t notice and thread damage before starting the job, I have owned the car from new and this drive shaft nut has never been removed before.

I don’t want to jump to conclusions but in all my experience I have never seen threads stripped by removal of such a nut, if anything I would expech the nut to clean these theads if the were damaged before. I grew up through motorsport and prerparing cars, and also have 40+ years of experience as an electro mechanical engineer, I can find no such weakness previously reported on Google so seaking experience and opinions of others.

Thx in advance,

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• 4c91b3460efd5cea2e861f284ac6a159

Topic

[Billy]

Was he replacing a wheel bearing? If so, has the new bearing been installed yet? If not, hard to point to any specific series of events. If so, a dozen Krispy Kremes says he used his big-ass impact wrench instead of his torque wrench to install the nut.

[Jack]

It went in for a wheel bearing, I was told the nut turned slightly them became tight, after forcing it off this was the result.

I have been working on cars for 40 years as a hobby and have never experienced threads being damaged removing a nut. If anything I would expect any pre existing thread damage to be cleaned up by removing the nut? The garage are adoment, I haven’t found any similar reports on the web and I would hate to accuse anyone in the wrong.

[Billy]

So was the new bearing installed or not?
If not, another possibility is that he turned the nut the wrong way.
A third possibility is that it was over-torqued at the factory and was already stripped.

[Jack]

Sorry, the new bearing was installed and the result of the damage the driveshaft is now replaced (by dealer)

My thinking is any thread damage should have been evident before removing, I have never seen threads stripped when removing a nut from good threads. Nothing on that side had been removed, I have a 35mm socked but realised it was a job for a press so left it to the dealer.

[Mike]

From the look of it, I’d say the damage was done during assembly, not disassembly.

Usually, a new nut is required when assembling the axle. Looks like the old nut was reused and forced with an impact tool right from the first thread, instead of finger-starting the threads. You’re the victim of shoddy unprofessional work practice.

[Jack]

I believe Evil-i has uncovered the mystery, I always thought it was likely the damage had been caused by a short socket on an impact wrench while attempting disassembly. I was contacted and informed the nut had become tight during removal and asked what I wanted to do, without photos or video I could only say remove it otherwise I would have no car. The mechanic said he might be able to clean up the threads but when I eventually saw the drive shaft and damage that was never a possibility. I could also see no possibility that this thread damage was caused by nut removal. Even if the threads were damaged in any way previously, which they were not, nut removal would have cleaned them up slightly rather than causing the damage seen here.

I say again this was a certified Mazda dealer and not some back street cowboy so I would expect better, and the service manager of the dealer informs me he has discussed the problem with Mazda technical? I also find it strange the same dealer provided me with a video summary after my previous routine service where there were no problems other than a rattling heat shield on the exhaust, I wonder why they never did the same or took photographs to support this story?

Firstly a new nut does come with the bearing but on the day I was contacted as they couldn’t get the hub removed and suggested removing the whole drive shaft to take it to the press for removal. It would now seem at that point the old nut was put on temporarily, cross threaded and probably with an impact wrench as Evil-i suggested. It would appear the reason why no photos or video were captured when “the nut became tight” was because the old nut was already removed the drive shaft.

Finding the Mazda dealer’s version of how the damage occurred hard to accept and the fact they were pointing to the Mazda part as not being serviceable, I naturally asked for all the bits back to follow up with Mazda themselves.

I believe the photo below of the old nut inner and outer now support the opinion of Evil-i and answer my doubts as to how this could have happened, thank you for taking time to post.

I will be returning to the dealer, although never using them again, a little honesty and integrity goes a long way and how their service manager could choose to support the technician’s version of events when seeing the evidence for himself is now beyond me.

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• 5307f94de82839fd3ebbf3fdfb07f6e4

[Antonio C Michael]

That damage looks like it was done during assembly also looks like it was stripped during the use of impact wrench

[Matt]

Assembly line or a mechanic who realized the problem, but forced it on so he didn’t have to deal with slowing things down or costing his boss more money. Gotta love that lack of integrity.

[Antonio C Michael]

I agree with you flintiron didn’t want to slow the repair down and cost there boss more money

[Jack]

Thank you everyone for your input, forcing myself to look at things in more details and present here has made things very obvious.

I will be returning to the dealership and presenting my case again, thankfully I just didn’t accept things at the time and asked for all the old parts to be left in the vehicle. Sadly so many owners would just trust their workshop and accept things as they were put to me at their loss and no consequences to the dealership or their reputation, just the poor owner picking up the bill.

[Author]

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