[LionOfGosforth]

I'll try to keep this short as I feel a bit stupid about the whole thing. Past few weeks, noticed a stuttering under acceleration and also deceleration. A recent visit with an independent mechanic indicated there may be some HPFP codes in the computer so, while at the dealer for recall work, asked them to check it out, hoping it would be something simple or something warrantied. Turns out, issue is within the transfer case. They then proceed to tell me that one of my rear tires is the wrong size. I had one replaced a month or two back, knew it was a different brand, but was told the size was correct. Had this done at a TFT. My bad, didn't even think to check the sizing on the sidewalls etc. Seems fairly cut and dried the wrong sized tire is causing this. So, 2 questions spring to mind:

1) how do I approach this with TFT? They are completely on the hook here right? Not just my stupid fault I didn't notice in the first place?

2) If they simply and effectively replace the tire to one correctly sized, will the symptoms go away or is it inevitable that the TC suffered damage and needs replacing?

Dealer already said ballpark 3k which is ludicrous to me. Any guidance greatly appreciated.

[nsjames]

the transfercase is a clutch design.

making the driveshafts spin at different speeds wears the clutches.

Is it damaged? Who knows.
Did you shorten it's lifespan? Absolutely.
Does it at least need a fluid change and it's adaptations reset. Yes. That fluid is probably full of friction material.

Not sure what TFT is, but they at least owe you a new matching tire, and if you really want to push, possibly a new transfercase. Assuming the dealer will back you on the damage or wear that it has incurred as a result of them mounting the wrong tire.

also, 3k isn't ludicrous if they're installing a new transfercase.
that shit ain't cheap.
https://www.bimmerworld.com/Drivelin...xoCOD4QAvD_BwE

even reman units are $1500.

[LionOfGosforth]

Originally Posted by nsjames

the transfercase is a clutch design.

making the driveshafts spin at different speeds wears the clutches.

Is it damaged? Who knows.
Did you shorten it's lifespan? Absolutely.
Does it at least need a fluid change and it's adaptations reset. Yes. That fluid is probably full of friction material.

Not sure what TFT is, but they at least owe you a new matching tire, and if you really want to push, possibly a new transfercase. Assuming the dealer will back you on the damage or wear that it has incurred as a result of them mounting the wrong tire.

also, 3k isn't ludicrous if they're installing a new transfercase.
that shit ain't cheap.
https://www.bimmerworld.com/Drivelin...xoCOD4QAvD_BwE

even reman units are $1500.

Thank you for the reply. TFT = Town Fair Tire.

When I said "ludicrous" I didn't mean the actual price, I meant from the point of view of my having to pay it because someone else made a mistake.

I am picking up from the dealer tomorrow, then will see what TFT say. Thanks again for the response, appreciated.

[nsjames]

well who is going to pay is up to TFT. If they admit fault, their insurance will pay.
If they tell you that they'll give you a tire, but refuse to pay for a transfercase, then you're going to pay, and have to attempt to recoup your money via the legal system if you want it replaced.
Alternatively if it drives OK after, you could take the risk on it being fine for the life of the car, but it has sustained accelerated wear. There's no way that anyone can deny that. How much wear? Well that's the $64K question.
Do you have your original receipt for the tire, and does it list the correct size?
that may be their out. They will claim that the tire size was listed on the invoice and that you approved the invoice, thus absolving them of liability.

3K is well past small claims court money, and firmly into hire a lawyer money.

I'm not saying that's how you should approach it right off the bat, but if they don't give you satisfaction that's exactly what I would tell them I was prepared to do.
especially since you have the dealership backing you on transfercase damage because of the wrong sized tire.

[LionOfGosforth]

Ok quick update. I got my car back this morning, the SA mis-spoke. The tires are not mis-matched in the way he said, he was trying to say there's a staggered setup, which is true, had it for years. Anyway, my setup is pretty mild or so I thought:

front - 225/40/18
rear - 255/35/18

I don't think that should be a big issue but maybe over time? Is this setup considered ok and I was mistaken? Should I go back to a square setup?

[nsjames]

there a great big thread about the staggered tires and somewhere there's a list of acceptable tire sizes.

they need to be within 1% rotations per mile.

also yo uneed to bear in mind that tires do not run true to size, and different manufacturers either run small or larger in the size. It's like clothes. So take care mismatching manufacturers as well.