What do you guys think about a 4.10 with the ZF?

[Eric]

I'm running a 3.73lsd right now and hardly use 5th on track, so i've been thinking of going to a 3.91 for a while, but a 4.10 small case might be really cool!

Also do you think a small case diff can handle 250rwhp?

[trackjunkie21]

I'm running a 3.73lsd right now and hardly use 5th on track, so i've been thinking of going to a 3.91 for a while, but a 4.10 small case might be really cool!

Also do you think a small case diff can handle 250rwhp?

No way it will handle that power, my small case crapped out behind an m50, and why would you want such short gearing? 4.10 with my g240 was horrible, can't imagine with a ZF

[drumad]

why not a 4.10 med case? I don't know the weight difference between a small and medium but I can't imagine it to be too much.

[trackjunkie21]

why not a 4.10 med case? I don't know the weight difference between a small and medium but I can't imagine it to be too much.

Don't know exact numbers, but it is substantially heavier, but I wouldn't skimp on something like that, medium case all the way.

[The Dark Side of Will]

I'm running a 3.73lsd right now and hardly use 5th on track, so i've been thinking of going to a 3.91 for a while, but a 4.10 small case might be really cool!

Also do you think a small case diff can handle 250rwhp?

The weight difference is 20-25lbs... not a big deal, but not zero.

Do you have a small or medium case now?

Obviously you can't use first with gearing like that. If you dropped you FD to the point that you could use 5th, would you end up not using 2nd?

[e46s54dr]

The small case lsd's tend to overheat and fail alot sooner just based on the principle that its smaller and has less leverage between the dog ears and clutch disc. Though its 20lbs lighter than the medium case version, Id stick to the larger one.

[Eric]

No way it will handle that power, my small case crapped out behind an m50, and why would you want such short gearing? 4.10 with my g240 was horrible, can't imagine with a ZF

What kind of driving are you doing? I'm sure drifting will cook a diff fast, but I think I'm pretty smooth on track...

why not a 4.10 med case? I don't know the weight difference between a small and medium but I can't imagine it to be too much.

I figure if I'm going to go up in ratio, might as well try and save 20lbs.

The weight difference is 20-25lbs... not a big deal, but not zero.

Do you have a small or medium case now?

Obviously you can't use first with gearing like that. If you dropped you FD to the point that you could use 5th, would you end up not using 2nd?

I currently use 2nd very rarely, and my euro S50 has enough torque to pull out of tight corners in 3rd. I was actually downshifting into second in places that 3rd ended up being faster.

The small case lsd's tend to overheat and fail alot sooner just based on the principle that its smaller and has less leverage between the dog ears and clutch disc. Though its 20lbs lighter than the medium case version, Id stick to the larger one.

Hmmm, so to counter the overheating I'd have to install a pump and heat exchanger which would negate the 20lb weight savings... well that sucks. Does the Z3 diff cover fit on the small case?

[Jonny Cash]

M- coupe cover, and the thickest heaviest duty gear oil you can find.. Do it.

Dont let anyone who hasnt used high heat fluid in a small case tell you that it will blow. Go out there and find out first hand, and post pics of the carnage!

[Eric]

and post pics of the carnage!

:rofl::rofl:

I'll definitely be packing my current 3.73 as a spare!

[e46s54dr]

According to Vac and Turner, the M-Diff cover should fit on the both the small case and medium case.

[trackjunkie21]

What kind of driving are you doing? I'm sure drifting will cook a diff fast, but I think I'm pretty smooth on track...

This is my daily car with some spirited driving here and there.

[nrubenstein]

It'll be pretty hideous on the highway, but should be fun on track. Assuming that you have an 8k rev limiter, you'll be running out 5th on a lot of tracks, though.

[Wanganstyle]

According to Vac and Turner, the M-Diff cover should fit on the both the small case and medium case.

BMW makes the 168mm and 188mm differential units. The 188mm case housing has a different # of bolt holes than the 168mm unit.

Z3M diff cover was designed by bmw for the Z3M (all 188mm units). One can X reference the Part number of the paper gasket between the 168/188mm units to see the difference

What kind of driving are you doing? I'm sure drifting will cook a diff fast, but I think I'm pretty smooth on track...



I figure if I'm going to go up in ratio, might as well try and save 20lbs.



I currently use 2nd very rarely, and my euro S50 has enough torque to pull out of tight corners in 3rd. I was actually downshifting into second in places that 3rd ended up being faster.



Hmmm, so to counter the overheating I'd have to install a pump and heat exchanger which would negate the 20lb weight savings... well that sucks. Does the Z3 diff cover fit on the small case?

The thermal stress is less a worry than the torque of a healthy 3000cc engine. the 168mm units have a brittle top cap that shatters - a billet top cap would remove this problem. Differential internals are another issue; the 168mm design does not allow additional clutch discs/steels to be added with out custom modification. 188mm differential units were designed to allow easy configuration to suit quite a few OEM applications.

168mm stock LSD rebuilt to 100% oem stock specs may not handle real slicks on track for extended periods; the original organic clutch disc material is often seen melted in stock 188mm diffs.

168mm ring and pinion themselves are not rated for 3000cc power but will take it if ran with cooler on the track with a kind driver.

if driver does run the car hard a modified 188mm unit would be much advised. OR a high quality Aftermarket LSD in 168mm like a KAAZ or OS Giken unit.

4.10 would be great for short tracks with 8k rpm; an overdrive 6th gear would be nice if car is not trailered to the track.

pictured below is what happens to 168mm OEM LSD units.

Ring and pinion were undamaged, diff clutches and internals still in operational order. The bearing caps were keeping this entire unit togeather
This 168mm LSD was paired with a 100% stock M42 1900cc of fury. 100% stock car. Halfshafts un-damaged, diff mounts and bushings undamaged.

[e46s54dr]

^ Youre correct, on their website they say it will fit both 325i/e and m3s. I thought the e30 m3s came with the small case but they come with the medium case lsd after all. So the cover will only fit the medium case.

[gobuffs]

I ran a 4.10 (medium case) on my Euro 3.2 years and still run it on my S54. With the tires I'm running the theoretical top speed is 153. I was hitting 143 at the end of the back straight at VIR. A better launch out of oak tree I could be nudging the speed limiter. I don't see many tracks where I'd need more than 153...maybe in the future.