No more r3vtard assist

[Earendil]

Are your tires hopping/scrubbing?

Sent from my GT-N7100 using Tapatalk 2

Really hard to tell. dry pavement has been spotty at best around here recently, and my tires are into the nasty rubber until I can get an alignment and get the new rubber on. Certainly they aren't "hopping" like one feels in a locked 4x4 on dry pavement.

I'm going to say that they have to be scrubbing some. I jacked up one of the back wheels, put the car in neutral, and applied a torque wrench to the axle nut to see when it would break away. I know this won't give me an absolute number, but it'll give me a comparitive number since the SpecE30 racing class tests "stock" diffs at 65ft/lbs using this method. Mine didn't brake away until around 125 ft/lbs give or take. Youch!

So for anyone that has driven a high locking diff, do you ever hear sounds that are more metallic in their sound? Or do you only hear increased "whurrr" from the clutches, and rubber/pavement popping/hopping?

[Earendil]

Are your tires hopping/scrubbing?

Sent from my GT-N7100 using Tapatalk 2

Really hard to tell. dry pavement has been spotty at best around here recently, and my tires are into the nasty rubber until I can get an alignment and get the new rubber on. Certainly they aren't "hopping" like one feels in a locked 4x4 on dry pavement.

[Wanganstyle]

Are your tires hopping/scrubbing?

Sent from my GT-N7100 using Tapatalk 2

[Earendil]

Question about identifying sounds made by the differential after a rebuild, and quite possibly related to the additional material inside the clutch assembly causing increased lockup.

Driving in A:

• Straight line: No noise.
• Tight circle slowly: mild rubbing/slipping sound (does not sound damaging)
• Tight circle quickly: no change from above.
• Driving in loose circle slowly: Metal popping sound. If I didn't know better I'd say it was a U-Joint binding and letting go.
• Driving in loose circle quickly: Metal popping sound starts to go away above 20mph.
• Straightening wheel from loose circle to straight: Metal popping sound for a few seconds after the wheel is straight, and then goes away.

Tight = Wheel lock.
Loose = half a steering wheel turn.
Fast = On edge of losing grip, unless speed stated.
Slow = Jogging pace

At speeds over 20mph I can hear nothing. The rubbing/slipping sound might get drowned out by road noise, but the metal popping sound couldn't be drowned out by anything but a piston deciding it wants to see the outside world.

Is this what a overly locked diff sounds like? Or could something else be going on internally?

[Wanganstyle]

deleted

[JinormusJ]

Lots'o good friggen info coming out of this one

So wait.. You're telling me torsen diffs aren't the be all-end all performance mods for the rear diff choice?
For a trackable street car, I'd still want a clutch based LSD?

[Earendil]

Question: when piecing it all back together, what does it mean if while tightening the drivers side (pinion side) flange (#4 here) the input is easy to turn except for one small section, maybe 3 or 4 teeth on the pinion gear?

Then, if the flange is tightened snug, everything locks up and it can't be turned by hand?

I'm guessing this is that precision shimming aspect that is talked about. However, the clutches were the only thing changed, and everything went back on its respective side. Of the six bolts for the flange, I am able to properly torque down the forward most (input side) 2 bolts and it still turns smoothly with just a tiny bit of lash. The problem lies in tightening the rear most bolts anything more than finger tight.

Is there a likely thing (or set of things) that I could have done wrong on reassembly that would have this effect? I measured the shims, and the thicker shim is on the pinion (problem) side. I believe this means that I didn't mix the shims up.

I'm also not sure mechanically what it means that- as it gets tighter, the resistance starts with a few teeth and lack of backlash. Doesn't this mean that the pinion gear is crooked? Or is there another explanation?

I found a solution, that might also be the cause. I've disassembled and re-assembled the diff 4 or 5 times now, so we'll dismiss the possibility that I just tightened something different this time.

I removed the entire center stack and tried to assemble based on the advice of the ever-amazing Wangastyle, and everything torqued up just fine, without resistance. It would seem that my center stack is too thick, and this might be causing some sort of warping of the stack, even though the allen bolts tightened down without leaving a perceivable gap.

Lessons learned.

[Wanganstyle]

deleted

[The Dark Side of Will]

An Open diff with giant hoosier tires on the ideal surface will have as much grip for an underpowered car as the torsen, clutch lsd units will :)

If you don't have a wheel spin problem with an open diff, you don't need an LSD!

[Eric]

I like lubo moly 75-90 for bmw oem lsd units with no additives.

Spec e30 rules has a oem diff static lockup test method and you can do similar for a diff on the ground.

Fix the imput pinion and one output shaft to not move: then put some bolts in the other shaft and apply torque- a good stock diff shouldn't break free easily with human force applied: a dead one will give way internally

Thanks for both tips!

[Wanganstyle]

deleted

[bubbajan21]

Can you discuss a bit about the Z3 Torsen Units. I'm thinking of replacing my 3.25 LSD on my S50 car with a 3.15 Torsen from a Z3. From what I've read, it seems like it's superior at putting power to the ground so long as you're not lifting a drive wheel or stuck in the snow. For a weekend/good weather street car, would a torsen be a better way to go? Also, I believe the Z3 diff will drop right out of the Z3 and straight into the E30, correct? Lastly, what fluid would you recommend for the Z3 torsen unit?

Thanks!!

[Earendil]

Question: when piecing it all back together, what does it mean if while tightening the drivers side (pinion side) flange (#4 here) the input is easy to turn except for one small section, maybe 3 or 4 teeth on the pinion gear?

Then, if the flange is tightened snug, everything locks up and it can't be turned by hand?

I'm guessing this is that precision shimming aspect that is talked about. However, the clutches were the only thing changed, and everything went back on its respective side. Of the six bolts for the flange, I am able to properly torque down the forward most (input side) 2 bolts and it still turns smoothly with just a tiny bit of lash. The problem lies in tightening the rear most bolts anything more than finger tight.

Is there a likely thing (or set of things) that I could have done wrong on reassembly that would have this effect? I measured the shims, and the thicker shim is on the pinion (problem) side. I believe this means that I didn't mix the shims up.

I'm also not sure mechanically what it means that- as it gets tighter, the resistance starts with a few teeth and lack of backlash. Doesn't this mean that the pinion gear is crooked? Or is there another explanation?

Edit: I just watched a video on setting up diff backlash, preload, and contact patch. I'm a rather visual person :)
This combined with loosening the non-pinion side and still having an issue leads me to believe that the resistance is caused by negative lash and binding of the pinion gear, instead of preload. Is that summation correct?

[Wanganstyle]

deleted

[Earendil]

Yes image is not correct for small spider washers

The hardened washer is the most outboard
Spring washer is next and cone points towards Centerpoint of diff
Keyed washer with oil diamonds are next, diamonds collect oil for spider gear contact


Sent from my GT-N7100 using Tapatalk 2

Great! So for the keyed washer, the textured side of it faces towards the center?