Front and rear diff swap, 3.91 to 3.73

[dal.a]

Before i take a gamble can anyone share any advice?

My face lift 2006 E53 3.0D started leaking oil from the out put shaft seal so i had the diff removed and took it to someone that can actually repair them, it turns out the carrier snapped in two so it's now scrap.

I can get an exchange unit with BMW but its £1600 plus VAT so nearly 2k. Now i can get a 3.73 front and rear diff so is it as easy as just swap them both over, will it have an effect on anything else?

Any input would be a great help.

[dal.a]

Well i've been impatient and took the plunge, i have sent one of my drivers to pick up 3.64 front and rear diffs. Lets see how this goes.

[X5-D-Sport]

I have a spare rear diff for my 2004 E53  218  Diesel Sport face-lift - yours for £200 if you want it.

[dal.a]

As I wrote in my second post I have new front and rear diffs I'm just in the process of getting them swapped over.

The rear needed the flanges taking off and putting on the new one as the bolt holes didn't match up to my drive shafts but I think the front is a straight swap.

[Greydog]

Hmmm whether the diffs you are fitting 3.73 or 3.64 ratio that is a significant increase in ratio over 3.91. I would think that will reduce the rate of acceleration and will put extra load on the diffs, though it will also reduce engine rpm at cruising speed.
The reduction in RPM may drop the engine off the sweet spot making pick up seem sluggish in the mid range. Then there is the speeedo, I cant remember if the speed sensor is on the gear box or a front hub. If it's on the hub it will read OK if it's on the box it will be out by 7 or 8%

[ianst0028]

I thought the speedo was taken off the p/side rear abs sensor

[dal.a]

Update. It's all done and is spot on, speedo is the same as its from the hub, there's no real noticeable difference in the way it drives, the diffs are from a 2005 3.0d X5 whereas mines a 2006 3.0d, as far as I can see the 3.91 were fitted in the 4.4's so I can only think they are in mine as its a very late one?

[R77YDS]

[quote="dal.a"]
Update. It's all done and is spot on, speedo is the same as its from the hub, there's no real noticeable difference in the way it drives, the diffs are from a 2005 3.0d X5 whereas mines a 2006 3.0d, as far as I can see the 3.91 were fitted in the 4.4's so I can only think they are in mine as its a very late one?
[/quote]




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[R77YDS]

Hi just wondering how your diffs are getting on as I also have a broken carrier in a 3.91 rear diff and been thinking of doing the same job ?


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[dal.a]

It's been spot on mate. Perfect solution for an expensive problem.

[the shreksta]

Which model do these diffs come from

[dal.a]

The 3.64 I fitted were from an earlier 3.0d I believe, mine is a 56 plate so I'd imagine pre facelift.

[steve1986]

Hi Guys,

I need a 3.91 rear diff for my X5 unfortunately as it exploded  >:( , does anybody have one available ?.

Thank you

[henrym3]

From an interest point of view, why are all these diffs disintegrating. 

[X5Sport]

I'm probably out on a limb here, but my guess is tyres.  Either wide tread difference now or in the past, or use of non-approved tyres on staggered set ups.

I suggested that perhaps as the value of these cars falls justifying £800 on a full set of rubber becomes much harder.  The risk is that a poor choice could destroy a diff.  Some non-approved sets have a rolling difference of >30mm and that cannot be good.

I might be wrong and am happy to be educated if there is another reason.