Need to make a "diff"erence

L

LittleZ4

Active member
I know the diff question has been asked a lot, and there's a lot to search through, but can I pick the brains of the collective group.
I have a PF (pre facelift) 3.0i manual, so the diff is the 3.07fd. 188k casing.
Doing a Google search if shows that the E39 and E53 use the same diff. Can I take the diff from an E39 and change the rear plate to the finned type to make it fit the zed??
I'm also assuming that FL diffs fit PF cars?

Ideally I'd like to get a 3.46fd but the FL 2.0i has a 3.38 which could do??

If there's a list somewhere of diffs that we can use that would be brilliant......think I've punched most of the diff codes into real OEM now :roll:
 
Cheers for the list porky :) I assume the diffs on that list will fit the z4 then?

Are these ratios applicable to the UK spec cars?
 
No, that list is specific to US cars only. There are a lot of similarities, but you need to take it with a pinch of salt as some of them are wrong. For example the UK pre-facelift 2.5i typically has a 3.23 final drive ratio where its listed as 3.46.
 
Hi,

I can recommend the 3.46, ratio. 1st is still usable, no problem there, 6th is a little less of a cruising gear on the motorway, just a little less.

2nd -5th, you've obviously got more pull thru the rev range, and you can feel it too. 2-5, the gears feel a little shorter giving the car a bit more of an old fashioned feel where you can work the box thru when driving along your country lanes.

Really pleased I went for it.
Cheers mark
 
i did a diff swap back in the day on an E46 328i track car... cant remember the exact ratios (original was either a 2.93 or a 3.07, and swapped it to either a 3.38 or a 3.46).

But either way, i echo what Bmwforachange says - very noticeably more punch coming out of slower corners, 2nd, 3rd and 4th all nice and punchy. fairly easy to work out what the effect will be on top speed in each gear - i think after the diff swap 2nd topped out at 58mph (down from 63) and 3rd topped out at 85mph (down from 95). i think motorway crusing in 5th gear was maybe 300rpm higher, but... definitely worth it for a sports car! it really did completely change the car. :driving:
 
Cheers guys. Looks like the 3.46 us the way to go.

Mark did you get your diff from another z4 or was it from a different model? I'm just curious if any bits need swapping or changing?
 
Hi pal,

Z4 3.0i auto, straight swap. It's worth giving the likes of quarry motors a call, they may have one even if it's not advertised.

Same for those been broken on ebay.

Good luck with it. Cheers
 
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