Differential replacement (twice?) on X3 2007

[milou500]

Hi guys,

Last visit at the BMW dealer (200 km away from home) was to replace 2 outside mirrors that would not heat anymore. They did not have them in stock but they took the opportunity at the same time to replace the...differential, because of a slight noise picked up during the road test. I actually heard that noise before but did not pay very much attention to it.

I am back to the dealer couple of weeks later and mirrors get replaced. After 400 km both way to the dealer, a high pitch noise developped in what I think is the differential (again...). It is very obvious at low speed (40 km/h) and upon decelaration. Had no problems during last couple of weeks of city drive and it seems like long uninterrupted trips could be related to this condition. What's wrong with BMW differentials? Any lube problems reported before? Have you ever heard of strange stories like this? Looks like I will have to revisit the dealer and probably be told once that they'll have to change the differential once again . Guys, any comments on this?

Have a safe Holidays season

[Tefal]

Mismatching of tyres causes transmission noises on the X3, really common and emails have gone out to BMW dealers on the problem in the UK.

People have been replacing diffs and transfer boxes, when all it is is the tyres, putting a new tyre on one side and having a worn old one on the other makes the noise bad due to the rolling circumference.

[milou500]

Well, yeah, I heard of this but my 4 winter tires are brand new and mounted on 17" steel rim (to save my aluminum rims). I am going to the dealer on Friday and let you know the verdict.

thanks

[milou500]

Guys, here the end of the story:
Differential got replaced a second time as expected. On the way back home, the tire pressure loss detector went off after several km. This indicates that wheels are not turning at the same speed because of a deflated tire. Checked the tire pressure and surprise, one rear tire was 38-40 psi and all the other one were 32 psi. This dates back from the time I installed brand new snow tires on steel rim early November. I remember resetting the pressure loss detector as I thought and overall change in tire diameter (winter vs summer) was responsible for this. I suppose that I have driven 1500 km with one over-inflated larger diameter tire and damaged the differentials. I probably did couple of mistakes and one of them is to buy and install tires at Costco where unqualified personnel left one overpressured tire on the car. Fortunately, there was no charge from BMW as I am still on warranty.
Anyway, I thought I would share this story with you all: watch pressure when you change tires as it could create irreversible damage to your car.

[canambmw]

A 6 to 8 lb. difference in tire pressure would increase the diameter of a tire by less than 1/4 of an inch. That would not be enough to cause a differential to go bad. However, a 20 lb difference may cause some problems over a relatively short time (weeks). Even new tires can have a 1/8" or more difference in rotational length.

Your diff problem was a diff problem caused by something other than a modest difference in tire pressure. If that amount of pressure difference caused that much damage, most AWD BMWs would all be looking for new difs.

JM

[Tefal]

BMW would replace the diff saying that it was knackered as they like throwing parts at car, I bet if you had found your tyre pressure problem just before you dropped it to the dealers the noise would have stopped,

Seen it loads on the forum I'm on regularly.

[milou500]

Okay, now second diff installed. Ran near 800 km short distance city drive without problems. Guess what: after round trip to Québec city (200 km each way of uninterrupted distance, this noise is back and amplifying while city driving. I am speechless...it is exactly what happened to the first one....and the tire pressure theory is indeed out.....

[fun2drive]

This could be a couple of things. There is a possibility that the diffs are having an manufacturing issue which could account for the problem.
Differentials have to be aligned correctly or the gears will wear quickly and cause problems. I don't know if any of these is the case but they are possible.
I don't think that an incorrect diff fluid could be the issue but again possible. What temps are you driving in when you start out?

I don't see this happening to other X3's so something is certainly up...

[milou500]

Thanks for your reply fun2drive. I agree with you that this is somewhat peculiar: I have not heard or read anything like this elsewhere. I am not quite sure I understand your question: outside temperature are quite low at the present time (25 to -30°C in the morning). Other X3 in my area are probably submitted to the same temperature. One thing I forgot to mention is that, upon arrival from my 200 km trip, I got out of the car and detected a smell like heated rubber or burnt oil. The brakes were not sollicitated that much and may be this is not related to the diff. issue. The other thing is that I have installed snow tires (same size as summer)on steel rims. I intend now to run this diff up until tires change and visit again the dealer for possible diff replacement and see what happen at that point. I know it seems odd but could my winter tires be the source of the problem? (Blizzak WS-70). Thanks for your interest and support

[milou500]

Changed back to my summer tires mounted on original wheels and noise completely disappeared. This is weird... Maybe steel rims may not be compatible with the xdrive but I can't really explain why.

[jv2000]

This is an interesting thread ... my wife's '06 X3 does the rear shudder at lower speeds when turning, like pulling into a driveway, etc. I'll have to check the tire pressure to see if that could be it ... short of that I've also read that the type of tire can have an effect. Milou500 seems to have noticed this with a change of rims/snow/summer tires and the problem goes away. So strange.

[TomWalken]

My 2007 X3 M series (19-255 tires in rear, 235 in front) came to me at 100,400 miles already on its second rear diff. Records show that at the replacement at 87,000 the diff they took out was non-OEM. So it's possible it was on its third diff when I got it. Still, I discovered a rear-diff growling noise in high torque/high resistance driving conditions (acceleration at +65 or up steep hills). I've got a used diff I'm having installed next week, but I do wonder about manufacturing defects more than issues with tire size or inflation. I have Pirelli P-Zeroes on all corners (not a winter tire, I can assure you). My BMW guru seemed obsessed with the tire size issue and did some calculations, but I'm not impressed that rolling diameter differences create much more stress than normal cornering. Plus, I don't think tire size would make the kind of growling noise I'm hearing. Both front and rear diffs are designed to handle non-matching wheel speed during cornering. Sounds like a bad bearing. I'll take the discarded diff apart to investigate for sure. Keep in mind, my growling noise is a different type of noise than that whining noise you guys are talking about. Could be a totally different type of problem. I'll Keep you posted. TomWalken