Output shafts keep breaking

[Kreindler]

So, my car is quite far from stock. And it sees quite some abuse.
My rear (diff, outputshafts) is still stock (from the nfl 520i).

I want to keep the diff as it is quite short and a lot of fun (3.46). Actually i even plan to change the ratio to a 3.73 but a little later given the situation now.

But unfortunately my output shafts keep breaking (left one broke in january, now the right one broke - same situation: they broke while i did a launch). So i need to upgrade them.

And I need some help:

1. With the 188k diff- what was the thickest outputshaft available (eur models included pls)? The one from the 530i ? 525d? Could i somehow use output shafts that were used with the 210 case diff (like for the 530d or v8 ones- are they the same length?)?

2. Besides the output shafts and the parts marked in the pic below - would i need anything else to retrofit stronger output shafts?


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[Jaaap]

Are you sure you don't want to upgrade to a 210 diff housing?
Surely 3.46 or higher is available there too (the e46 M3 has a 3.62, should be a 210 case).

[Kreindler]

Well I would.. but my money is limited and i have planned ither investments for now (contour seats and some other cool interior stuff) and a swap to a 210 case would mean:

Complete other rear axle
Modified shaft
210 diff (which if it is stock lsd it is far from cheap)..

So it would cost me around 1700$ at least including labour.

I could cut the costs down if instead of the lsd i get the 530d (also using the 210 case) parts which are widely available and not that expensive, but those have really small ratios..

And.. shouldn’t the 530i parts be enough, at least for now? I mean... my engine is stock.. and yes, the short ratio increases abuse by ~ 18% when compared to stock, but still- that should be ok, or?

I would for sure think of going for a 210 case later down the road when i start with engine tuning. But i am still not close to that


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[Kreindler]

After research on realoem i found the following:

The drive flange output on the 520i is 80mm.
The drive flange output on the m5 is 102mm

Good. Now:
I have a diff with a 188k case from an e53 3.0d lying around.
The drive flange output on this e53 diff is the same part as used for the 525d, with a size of 94mm (part number 33137509105)

So I could use the drive flange output from the e53 diff that i have and use them for my e39 diff, so that i can further mate them with some e39 525d/530d output shafts- PN 33211229749.

Thus- i would end up with a 188k case (so no change needed here) and the next best thing in terms of output shafts after the m5.


I will keep this updated but i think it will work.


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[JimLev]

Just make sure the C-clip that holds the flanges in is in the same location on the stub, otherwise they won't stay in.

[Kreindler]

@JimLev - Not sure which c-clip you mean... Could you help me with a partnumber (and eventually a screenshot from realoem? )

The thing is - the flanges that I plan to use (PN 33137509105) I will take with all bells and whistles from a working e53 diff, and according to realoem it was used in several 188k diffs. Including the 525d and the 535i from the e39 (which both had the 188k diff). So at least theoretically, and basing on that info - I don't see why it wouldn't fit.. Same diff case as it was intended to be used for, so it should work. Or am I still missing something?

The adventure that I actually plan here is even bigger though.
As anyhow I will have to also change again diff oil (just changed it 3 month ago)) ), I want to use the e53 diff for the actual purpose I acquired it for:
I will take the gearings from it and put it into my diff. Thus - i should end up on the rear axle with>
An open diff (still) with a 3.73 gearing, in a 188k housing, and with output shafts thicker than on the 540i.

If all goes according to the plan - the result should be quite reliable and... given the 3.73 ratio also fun

33137509105

[JimLev]

Look at your pic in post #1. The C-clip is part 19 and fits into the groove on the end of the spline on the flange.
Some flanges have the C-clip groove closer to the end of the flange where the axle CV joint bolts to.

[ross1]

Won't all this also require new axles? Will those axles mate to the existing wheel hub flanges?
As long as you piece meal this and continue to abuse it you will just be finding the next weakest link of what must be the weakest of all the rears.
An easier solution might be to exchange the entire subframe, diff, axles, etc. from a car with the stronger parts.

[Kreindler]

@JimLev:

Got it. But again: as long as i take all those parts from the e53 diff, and as long as this flange existed on this 188k case (on the 535i and 525d)- i can’t see how it could be in different positions. The parnumbers are the same.

@ross1:

Well the output shafts are the only things that i had to buy (already got them actually, now waiting just for delivery).

Thus i would have stronger output shafts, stronger flanges. The only part remaining “weak” is the diff casing which will still be 188k, but i am pretty sure that shouldn’t be a reason of concern, at least not up to 400hp (188 cases support quite some abuse on tuned e30s of over 500hp and don’t break that often).

And yes the weakest link will always break. Point is to get to the point where the weakest link is the tire.

From front to back now i have:

SMF (not lightened)
The zf320z (which again is known to support abuse, at least safe to use until 400-500hp)
530i drive shaft (which again should be ok- and if it breaks i will do a custom titanium one and that’s it)
188k diff with 3.46 ratio (3.73 to follow)
And to be added now:
94mm output flanges from the diff (same as on the 540i, 530d, 525d, slightly smaller than the 102mm m5 version, but still a beefy upgrade over my current ones which are 80mm as far as i remember)
Ø of the output shaft 38mm (so same thickness as the m5 or 530d or 525d)- even thicker than the 540i one.

So i hope i should be good after this retrofit and the abuse is pushed to the tires.

Do u think i should be less enthusiastic about it?) if so- what element do you think will still be regarded as “weak”?

My logic is:
All the way up to the diff- the transmission parts are what the 530i came with stock. And from there the ratio of the diff is way shorter (stock ratio is 2.93 if i remember correctly)- which means way more abuse for the following parts. Parts which will suffer some considerable upgrades now

Would maybe adding a LSD also help? But the open diff should anyhow send the movement to the part with less resistance- so i guess lsd will add more abuse on following parts, not less.


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[Kreindler]

Update:

Works as intended!
So with the output flanges from another 188k diff (either the 525d or the e53 3.0d automatic)
Plus output shafts of the 525d/530d- perfect fit for any e39 that came stock with a 188k diff.

So now i have thick output shafts that should withstand some good abuse

Can’t wait to try it but there is some other stuff on the to-do list until i get to drive it again


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[JimLev]

How much abuse can you dish out from a 520 engine?

[Kreindler]

It’s not the 2.0 engine anymore check signature


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