Differential problems.

[mbmw]

The rear differential on my 2005 X5 with 230,000 miles has decided to pack it in and as a result I’m left trying to find a replacement.I’m definitely not going to be forking out for a new one.So I have searched for a used replacement with the 3.91 ratio.My problem is that these seem to be very scarce now.My other option is to replace both the rear and front diff with a 3.73 version which I can get relatively easily.Has anybody out there done this or does anybody see any potential problems with this?Thank you for any help in advance.

[Ricky Bobby]

I would match the front and rear diffs.

The 3.64's off the 4.4 can fit if you find used ones at a junkyard

[mbmw]

Hi Ricky,

Thanks for reply. I probably should have mentioned that mine is a 3.0 diesel. Anyway I have found a matching front and rear 3.73 and hope to collect later today. As with your comment, I agree with the need to match them otherwise I imagine some nasty munching. I'm just hoping that I don't have any other problems regarding mounts, etc or ECU. Though I don't believe there are any sensors that would be affected by the change in overall final ratio. in other words It's not going to be any different than if I put on a smaller set of tyres/tires. I would just love to know if anyone else has done this...

[Ricky Bobby]

I would actually imagine replacing with 3.73's together should not only improve fuel mileage but keep you at slightly lower rpm on the highway so a bit quieter as well.

Guys have replaced their 3.0 (petrol) diffs (4.10's) with the 3.64's off the 4.4 and noted nothing but positives. gGo for it!

[mbmw]

That's good to know. Well at least I'm not a guinea pig. So a double benefit so. I also heard that the 3.73 diff is a much better one than the 3.91 as on mine. Better mileage would also be nice with the price of fuel. Thanks for the advice. I'm off this evening so to pick up the front and rear 3.73 diffs so. I'll report back with any details.

[Ricky Bobby]

Lookin forward to updates!

[bcredliner]

No sure but I think the speedometer will be off. You will be going faster than it reads

[Joshdub]

Where does the x5 get it's speed from? Everything I have found comes back to the wheel speed/abs sensor. If that is the case, I don't think the speedometer will be off.

[David.X5]

I agree. Speed is based on the right rear wheel sensor. Diff shouldn't matter. Changing tire size does matter...

[bcredliner]

Originally Posted by David.X5

I agree. Speed is based on the right rear wheel sensor. Diff shouldn't matter. Changing tire size does matter...

That would be great, is that something you know for sure?