LSD issue ...

[TorW]

Quote:

Originally Posted by Jim K. I only call 'em as I see 'em! The preload is specified in the Montreal factory manual (1.5kgm 'wet' for 25%) and the old ZF factory instruction sheets.

[genericwood]

I may not be the sharpest tool in the shed, but I'm smart enough to defer to Jim on this one! Jim, it sounds like my original set up used quite a bit more preload than you recommend. Perhaps that's why we have experienced different results? I also have not detected any wear in the plates, but I did find myself frequently reshimming for wear that was not detectable to the naked eye.

Erik

Quote:

Originally Posted by Jim K. I only call 'em as I see 'em! The preload is specified in the Montreal factory manual (1.5kgm 'wet' for 25%) and the old ZF factory instruction sheets. On driving the car on the track with/without preload, I will disagree with Erik; it really feels more positive and actually has instantaneous on/off response with preload. This is a fact verified with many other racers/trackdayers. As for the mechanics of engagement, you will see pronounced dents in the ramps on high mileage units, especially when the LSD is hard-worked, driving-wise, regardless of preload. When correctly preloaded, units required re-adjustment after a couple of racing seasons and interim daily driving and no wear was detected on any parts, requiring only a mere shim change to restore preload to the allegged 47% -thats what ZF says you get with 4 friction washers. Large BMW models (ca.1980-something) as std equipment had a strong and thick bevel spring washer at the end of the clutch pack, making for constant preload, requiring no or very rare restoration. Such washers are available for our cars from Bacci (Italy) but unfortunately they will only fit the 25% units. If you insist on using them in the 47% box, you'll have to machine the housing to accommodate the extra 2mm of these. Jim K.

[Jim K.]

Gooooood mornin' to one and all (it is, here).
Erik, I've never exceeded the recommended values so I don't know what happens or how it drives, but I've seen the pitiful condition a set of LSD innards came out in, when the genius mechanic decided to make his own 'locker' diff in a 105. Pity I didn't take pics, they'd be in the book, one just can't believe those...things were once friction plates!
As for the Montreal manual, its titled "Technical characteristics and principal inspection specifications" Alfa Romeo DIASS publ. #xxxx. It was available in both Italian and English (at least). I used to have it but some SOB swiped it long ago. In there, it says that when one wheel is held stationary, the other should turn when 1.5kgm is applied. Note that the Montreal ramps were 120* and NOT 90* as in the 2liter 105's and 116 series. Maybe this will account for the fact that in the same manual for the 2liter 105's (DIASS publ. #1821, English version) the torque given for the same test is 0.5kgm for 25%. Curiously enough, it also erroneously states the 'clutches are sprayed with molybdenum'. They must have confused it with the molybdenum metal content of the plates. Spray anything like that (i.e. MOS2) on the plates and there goes your LSD! On the subject of ramps, note that off-throttle understeer is greatly promoted when using 120* ramps. Ideally, we would like 120* on the load side and 90* or even less on the off-side. A good machine shop can do this easily by suitably milling the area between the existing ramps and subsequently apply some form of surface hardening.
BTW, these LSD's are all 4061 series, the DLxxx denoting the size if memory serves. Between 105 and 116, most inside parts are interchangeable.
Jim K.

[papajam]

Quote:

Originally Posted by Jim K. As for the Montreal manual, its titled "Technical characteristics and principal inspection specifications" Alfa Romeo DIASS publ. #xxxx. It was available in both Italian and English (at least).