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Matt
Matt, Mechanical Engineer
Category: BMW
Satisfied Customers: 21984
Experience:  BEng hons Mech engineering, in auto industry 22 years
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HiI have a 2006 E53 3.0d, the rear diff has destroyed

Customer Question

Hi I have a 2006 E53 3.0d, the rear diff has destroyed itself, the problem is locating another 3.91 ratio diff. My question is.....is it ok to change both the front and rear diff to a different ratio; say 3.64 which are both available? they are from a 2003 model, as far as I can see the only difference is the drive shaft flange which I can remove and replace with the one from my broken diff.

Submitted: 2 years ago.
Category: BMW
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Expert:  Matt replied 2 years ago.
Hello

providing you can get a dealer to update the software to recognise the new diff ratio then yes you can fit the taller ratio
the software needs updating so the speedo reads correctly

bear in mind its a reasonable step up in gearing so expect the acceleration to suffer but fuel consumption should improve on a long motorway run
Matt, Mechanical Engineer
Category: BMW
Satisfied Customers: 21984
Experience: BEng hons Mech engineering, in auto industry 22 years
Matt and other BMW Specialists are ready to help you
Customer: replied 2 years ago.
Hi Matt
Thanks for that, someone told me that it would destroy the transfer box.
Personally I don't see how, what is your view before I proceed to change the ratios
Expert:  Matt replied 2 years ago.
Hello

providing you match the front and rear ratios the transfer box will be fine
as you're not putting more torque through it as the engine is the same as before

the engine will be working harder on acceleration as the ratio is higher but the amount of torque transmitted into the transfer box is the same as before