The insides of my 3.91 rear diff have tried to escape through the case rendering it scrap.
There are none on the bay of e.
I've phoned 18 BMW breakers and none have a 3.91 but two have now told me you can fit the 3.73 so long as you do both front and rear together.
Aparently the front is a direct bolt on and you just have to swap over the 3.91 output flanges to the 3.73 on the rear diff. I've been offered a matching pair of 3.73's for £450 and there are loads out there should a diff fail again.
Anyone have any experience of this swap or know either way whether it can be done?
Not joined yet? Register for free and enjoy features such as alerts, private messaging and viewing latest posts and topics.
Broken 3.91 rear diff - swap to 3.73?
Broken 3.91 rear diff - swap to 3.73?
Last edited by Guest on Sat Oct 01, 2016 9:37 am, edited 1 time in total.
2004 E53 3.0d Sport, silver, black leather, heated seats, panoramic roof.
Re: Broken 3.91 rear diff - swap to 3.73?
2011 Kia Sorento KX3 2.2D 60 Plate Auto in black ( mine )
BMW E83 X3. 3.0d M Sport, 2008 in black ( now gone )
BMW E93 330i Convertible Msport 2007. ( Now sold )
VW Golf 2.0 TDI 140 GT 2010 ( now sold )
Now Sold 55 plate, X5, 3.0 D Sport. Silv
BMW E83 X3. 3.0d M Sport, 2008 in black ( now gone )
BMW E93 330i Convertible Msport 2007. ( Now sold )
VW Golf 2.0 TDI 140 GT 2010 ( now sold )
Now Sold 55 plate, X5, 3.0 D Sport. Silv
Re: Broken 3.91 rear diff - swap to 3.73?
Yes, I saw this post but Quarry bmw breakers thought the swap dubvious at best and FAB bmw breakers specifically told me it can't be done unless you change the transfer box too.
Does anyone have a working, none leaking 3.91 rear diff sat in their garage/shed?
Does anyone have a working, none leaking 3.91 rear diff sat in their garage/shed?
2004 E53 3.0d Sport, silver, black leather, heated seats, panoramic roof.
- Steamyrotter
- Snr Member
- Posts: 1304
- Joined: Sat Jul 31, 2010 11:06 pm
Re: Broken 3.91 rear diff - swap to 3.73?
If both front and rear diffs are the same ratio then the transfer box will be happy
The problems will be if you have different ratios front to rear
The problems will be if you have different ratios front to rear
If things were meant to be easy, then I will soon complicate them....
Please note...
Anything I say is only from my personal experience and knowledge..
I don't assume to know everything, and know there is a lot I don't know..
But then I could be talking bollox.. O:-)
Please note...
Anything I say is only from my personal experience and knowledge..
I don't assume to know everything, and know there is a lot I don't know..
But then I could be talking bollox.. O:-)
Re: Broken 3.91 rear diff - swap to 3.73?
Its my car in the other post and it definitely works, it's still driving perfectly and I've given it plenty of beans to try and make it fail.
Edit to say I didn't change the transfer box but had to swap the flanges over on the front and rear diffs.
Edit to say I didn't change the transfer box but had to swap the flanges over on the front and rear diffs.
Last edited by dal.a on Sat Oct 08, 2016 7:16 pm, edited 1 time in total.