E60 differential swap: replace 2.93 (manual) with 3.46 (auto)

[radarcontact]

Thinking about swapping out the manual rear diff (2.93) with one from an auto (3.46).


Would this be good or too much?? Looking to put some fun in my sons 2005 530i 6-spd w/~231HP.


Thinking it'd be a direct swap with no mods needed. Same part number, just different gears I think.


Thoughts???

(thanks)

// Radar //

[328 Power 04]

That's a nice gearing for acceleration, and not too drastic of a difference.

[TonyAngel]

It'll certainly add a bit of zip in the acceleration department at the expense of some top end that you'll likely never use or miss.

[dworthy]

Just to give you a visual to use: http://www.bokchoys.com/differential...calculator.htm

While this is a E-46, you can still plug in what you have into the boxes.
FYI the 6-Speed will have the same gears as a 330i.

And yes you will feel a difference, as you live in the U.S. who cares about top end anyway?

[radarcontact]

Just to give you a visual to use: http://www.bokchoys.com/differential...calculator.htm

While this is a E-46, you can still plug in what you have into the boxes.
FYI the 6-Speed will have the same gears as a 330i.

And yes you will feel a difference, as you live in the U.S. who cares about top end anyway?

yes, same as in my E46 ZHP convertible w/auto tranny I think. It goes nice!!

[shadowpuck]

agreed - 3.46 for a 330/6spd is quite awesome. the 5spd can be a bit annoying at prolonged highway speeds, but its manageable. on track, 330 really shines with a 3.46.

[bmwdirtracer]

I'd have one serious concern....but I'm sure Able could cure it for me.

We'd have changes in vehicle order, or coding, or programming, in an E60, wouldn't we, Abel? I mean, somewhere in all those 67 computers, SOMEBODY'S gonna get pissed off, aren't they ? No one knows better than you....

[radarcontact]

I'd have one serious concern....but I'm sure Able could cure it for me.

We'd have changes in vehicle order, or coding, or programming, in an E60, wouldn't we, Abel? I mean, somewhere in all those 67 computers, SOMEBODY'S gonna get pissed off, aren't they ? No one knows better than you....

Looking forward to an answer on this...(thanks for posing the question)

[dworthy]

Chris, I am not sure if programming would be needed, as in it won't throw the speedometer off.

Are you thinking the DSC may kick in as it thinks the clutch is slipping as the RPM's will be higher than usual?

[bmwdirtracer]

Andrea (E39 MGirl) swapped diffs in her E39 540, and it pissed off several computers....couldn't be fixed by coding, even though it was a stock ratio from another E39. I forget now how she fixed this.

[328 Power 04]

I am not sure how it wouldn't like a diff swap, but on E39 and on E60 it's a popular swap. Diffsonline and Turner sells tighter ratio diffs and don't mention of any such issues. Neither does a quick google search. In the DME and DSC, I do not see any coding provisions for any gear ratio.

Vehicle speed comes from the wheel-speed sensors on E60, so you wouldn't even have to deal with a diff speed sensor.

The only cars I really see complaining are the newer SMG cars, maybe.

[radarcontact]

All very encouraging!! So glad I posted here...thanks guys. Still trying to research, but for $200 I might just give it a whirl and swap it back if there's any unseen issues that arise.

[radarcontact]

I just hope everything lines up correctly, ref manual vs auto trannies. I thought I read somewhere that you had to swap something out - flange? - when you do this (new diff is from an auto, my son's diff is mated to a manual).

RealOEM says "Important! Drive flange and nut must not be replaced."
http://www.realoem.com/bmw/enUS/show...diagId=33_1161

Crap...so what does that mean to me, ref this project?? Who could I ask about this?

[shadowpuck]

i'd check to make sure mounting points, input, and output flanges. it looks like its all the same - you wouldn't be removing the input flange itself (but i'm not an e60 expert) so that note wouldn't matter.

[bmwdirtracer]

That quote refers to the fact that pinion depth is set using the driveflange and pinion nut. If you remove the flange and nut, and ESPECIALLY if you replace the flange, you're going to have to reset the pinion depth. (If the pinion depth is incorrect, you destroy the gears.)

This is not a home-brew job. You have to be able to read the ink blotches on gearfaces.

I will say that two techs have told me that they "do this successfully", But, well, I consider both of them to be hacks.....not because of their view on this, but because these two are, well....hacks, time after time.

If you're going to do this, maybe you can just mate two halves of 2 driveshafts, and have the assembly rebalanced at a pro driveshaft shop?

Or, as my friend shadowpuck says, maybe the driveshafts will match up?

I'm still not sure whether your cruise will work.....Abel, do you think this is okay?

[radarcontact]

i'd check to make sure mounting points, input, and output flanges. it looks like its all the same - you wouldn't be removing the input flange itself (but i'm not an e60 expert) so that note wouldn't matter.

That's what I'm hoping!

That quote refers to the fact that pinion depth is set using the driveflange and pinion nut. If you remove the flange and nut, and ESPECIALLY if you replace the flange, you're going to have to reset the pinion depth. (If the pinion depth is incorrect, you destroy the gears.)

This is not a home-brew job. You have to be able to read the ink blotches on gearfaces.

I will say that two techs have told me that they "do this successfully", But, well, I consider both of them to be hacks.....not because of their view on this, but because these two are, well....hacks, time after time.

If you're going to do this, maybe you can just mate two halves of 2 driveshafts, and have the assembly rebalanced at a pro driveshaft shop?

Or, as my friend shadowpuck says, maybe the driveshafts will match up?

I'm still not sure whether your cruise will work.....Abel, do you think this is okay?

I think you are talking about IF I were to mess with the flange, etc., correct? I'm just hoping to unbolt one and bolt up the other.

One saving grace in all of this...my son has a good-working 2.93 we can reinstall if there are any problems or issues with the "new" 3.46. And you know...doing it the second time will only take 1/2 as long! Hehehe

Thanks guys!

[bmwdirtracer]

I just hope everything lines up correctly, ref manual vs auto trannies. I thought I read somewhere that you had to swap something out - flange? - when you do this (new diff is from an auto, my son's diff is mated to a manual).

RealOEM says "Important! Drive flange and nut must not be replaced."
http://www.realoem.com/bmw/enUS/show...diagId=33_1161

Crap...so what does that mean to me, ref this project?? Who could I ask about this?

I was answering this question.

[E39MGirl]

Sorry for the late reply folks, but we have been away punting said E39 on a road trip and only got back this afternoon.

I managed to piss off the DME by leaving the 3.15 in our 540i when we converted it to a manual. If you do a search on this forum you will find quite a bit about others experiences with this if you search for "E39 3.15 cruise control".

Unlike the E39 M5 that has a second 'dumbass' switch on the gearbox that disengages cruise if you pull the car out of gear without touching the brake or clutch, the 540i/6 doesn't have that switch so the DME looks for a set RPM range/car speed combination to ensure the rpm is about right in each gear. If you pull the lever without touching the brake or clutch the DME kills cruise when the rpm exceeds the correct range for that speed. The problem is the DME also kills cruise if you have a diff in the car that results in engine revs that don't match the car speed within the ranges expected by the DME.

Our car already had the S204 option (short final drive - 3.15) so our (poor) assumption was that when coded for the manual all would work as intended. The problem is that S204 was not an option on the manual car, so the DME cracks the sads and cruise control doesn't work properly. Guys on here have run 3.15 diffs in E39s by using some clever coding that changes the rpm/speed tables in the DME, but given we here live in the land of long distances we decided to just change the car to the 2.81 ratio fitted as standard to the E39 540i/6.

I can't speak for the E60 as I don't know if the DME uses the same rpm/speed tables as the E39 to prevent bouncing the car off the limiter by pulling the car out of gear without killing cruise first. You would probably need to do the above search and speak to the guys who came up with the fix for the 3.15 into the E39 to see if the same issue exists for the E60, or just swap the diff over and see what happens. If it kills your cruise (or makes it really 'touchy', as in the case of the E39) I guess you could talk to the programming guys about building some code to fix it - or just live without cruise? Unfortunately, I can't tell you if it would affect other systems on the E60.

Andrea

[radarcontact]

Thank you very much for the detailed post! We are going to swap it out on Saturday, so the first thing we'll check is the cruise. Awesome input...thanks again.

// Radar //

[radarcontact]

Swapped out the diffs last Saturday...happy to report there are no problems, no drawbacks, no regrets.
Car is more responsive, although not as big a "diff"erence as we'd hoped, but significant nonetheless.

Cruise works fine, it has been used multiple times every day for over a week now.

Notes to anyone thinking about doing a diff swap:

Things you should have in hand before starting -
1) get an exhaust gasket (optional, but...)
2) you will need ALL NEW BOLTS which will cost you around $60 (6 of one size for each axle {12} plus 6 different size for the driveshaft. NOT OPTIONAL, they must be replaced.
3) of course, fresh gear oil (we chose RedLine synthetic) and maybe new plugs. We bought a magnetic drain plug from ECS for $20.

Things we learned -
A) this took 4+ hours on a lift. Can't imagine doing it without one. Also, try to use one where wheels can still turn freely...helps immensely with torquing which still takes forever. Also, have a friend help you, you'll need it.
B) remove the exhaust. We were stubborn and worked around it...trust me, DROP THE EXHAUST! Lol
C) fill the new diff with fluid before installing it (kind of a no-brainer)
D) axles came right off, but driveshaft was stubborn. Wood block and sledge, or similar on all sides helped break the bond. Also, there is a "key slot" machined into the driveshaft where it meets the diff...the slot is completely within the shaft, it is not the split point between the shaft and diff. In other words, don't try to split that notch, but instead use that notch with a hammer/mallet and flat screwdriver, etc, to drive the shaft in the direction AWAY from the diff. This will make sense once you see it, lol.

// Radar //

[shadowpuck]

thank you for reporting back to let us know how it worked out!

have you noticed much change in fuel mileage?

[radarcontact]

Your welcome, no problem!

The rpm change at highway speeds is about 500 rpm. No real loss on the highway, and I think he gets better around town because he's not stepping into it as much.
Net zero I would say, but we are going to look at it over a month to know for sure. He was getting 26 MPG prior to the swap.

// Radar //

[E39MGirl]

Awesome result, and awesome that you got back to everyone and posted the results!

Cruise can still work on the E39 but it drops out if you hit bumps and even on slight hills. If you have used your cruise a number of times in different conditions and so far so good then, fingers crossed, it is all good and we can leave the E60 off the PITA diff swap list.

[radarcontact]

Awesome result, and awesome that you got back to everyone and posted the results!

Cruise can still work on the E39 but it drops out if you hit bumps and even on slight hills. If you have used your cruise a number of times in different conditions and so far so good then, fingers crossed, it is all good and we can leave the E60 off the PITA diff swap list.

Lol, yeah sometimes these forums have great threads that read like a murder mystery...then you get to the end and realize no one posted who the killer was!! (Iaw, post is sorta worthless if you don't know the results)

He drives 50+ miles daily and about half of it is interstate-type highway with slight hills that he uses cruise control on, so we're pretty confident that it's good to go. However, if on different roads, under different conditions, etc., things change I will do an UPDATE right here.

Thanks for your inputs!

// Radar //