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S3 Limited Slip

7K views 72 replies 10 participants last post by  Stevew 
#1 ·
#2 ·
I'm not the expert here, but what I can tell you is the difference between our LSD and the video is that we only have 1 clutch disk per side and do not have the spring in the middle. Everything else looks the same.

Looking forward to the thread.

Good luck,

Vin
 
#3 ·
Thanks, Vin!

I'm looking forward to a positive outcome on this project. LSD clunk has been a major bug stain on the windshield of my life for far too long...
 
#4 ·
You sure it's the LSD? Every single time someone has had "differential clunk" on here, I think it's turned out to have been something else.

Well, except for one time where it was some broken pinion/ring teeth. But besides that...
 
#8 ·
Starting to wish I took Gubi’s advice.

After two months of thinking about the challenges ahead I finally began removing my LSD and unfortunately, found some advice here that somewhat oversimplified the situation. A lot more needs to be removed than I anticipated...

Pulling nuts off the left side of the diff and should have the LSD on my workbench soon.

Here’s a glamour shot of progress:

Vehicle Auto part Car Automotive exterior Wheel
 
#10 ·
Each lsd side has one internal blade and 3 external blades and unless something is really messed up won't "clunk". What can happen is the lash and preload on the bearings and pinion will be out of spec and it will "whine" under load. Even then it's not a common problem on a unmolested diff. The outer pinion bearing is the only bearing (only the bearing not the race) that can be replaced without going into the inner bearing, pinion gear, ring or crown gear, and left and right inner side bearings. You might have a trunion bushing that has gone south or trailing arm bushings that might cause a thunk aside from the driveshaft components.
 
#11 ·
Here is some of my foray into the rear end...
 
#13 ·
Thanks for the input guys.

And Gubi, engine mounts are aluminum units and center carrier was clunking when I got the car. R&R’ed and is solid.

OK, Now I’m confused about the clunk.

Scroll down about 1/3 this page to Diff Clunk. The 411 provided is what has convinced me to go in:


Also, my trailing arms, with only the fronts attached, can be moved through 18”. I know I have a lot of leverage but that seems a bit much. R&R’ed in ‘08.

”You might have...trailing arm bushings that cause a thunk aside from the driveshaft components.”

Hmmmm.

Finally, I stopped keeping a log years ago, but have discovered many of my efforts resulted in visits here and are preserved in the Archives. Sweet!
 
#15 ·
Soldiering on with my LSD project and because of considerable slop in both trailing arm front bushings, I pulled the left and knocked out the offending bits. Center bushing tube was loose. Thought I R&R’ed when I did the rear TA bushing, but unlikely these fronts failed in 30k and no witness marks of earlier mayhem. Two on order.

Also, since no metal on metal, would this “clunk”?

Auto part Vehicle Car
Bumper Auto part Automotive exterior Metal


I used the drill method to remove rubber around the center tube, then a hacksaw to cut a section of the outer. Had to go all Yosemite Sam on it for final removal.

Wondering if this has been my problem, but in for a penny...
 
#16 ·
If it were me, (and ive rebuilt a few diffs) the very first thing I would do is all the rear trailing arm bushes (like you are) and the sway bar bushes, and check the conical rubber bush that mounts the diff. Give the T bar a solid yank and see if its loose-- probably not.

If the pinion nut is loose, you can get some slop in the lash. Check the pinion nut on the diff, 75 ft/lbs roughly. If you have the pinion nut tight, and you still have more than a tiny amount of lash in the diff when you lock the crown gear, then its time to pull the covers off and check things out.
 
#17 ·
Thanks Goats (if that is your real name :)).

This thread is getting long so I’ll forgive you for not reading everything before you replied.;)

New conical bushes are on the workbench, rear TA bushes appear sound, and as noted front bushes are in process. New units arrived today.

T bar supports appear to be in good shape as well as anti-sway bushings.

A screwdriver through the filler hole locking the crown gear reveals no play at the diff input but when removed, considerable slop.

Im’a goin’ in!
 
#18 ·
So pinion to crown wheel has minimal lash. This is good. If you pull the big cover off you can pull the LSD unit right out. I’d advise to not change any diff bearings unless absolutely needed. If you watch those yahoos wheeler dealer episode on spider you will see that guy added extra clutch plates to the lsd. My advice- don’t do it
 
#19 ·
Thanks for the advice. If you review earlier posts, there is a link to advice about simply reconditioning existing clutch surfaces...my plan.
 
#20 ·
One of the benefits of being retired is having the luxury of being able to walk (or in this case, crawl) away from my repair efforts and chill for a bit. Did just that a bit ago as the LSD removal chore progresses. Oh, for a lift!

Here are some photos of today’s festivities, as the left drive tube came off, revealing a sight no Alfisti should ever need to see.
Auto part Vehicle Tire Engine Automotive tire
Auto part Vehicle Engine Automotive exterior Suspension
Auto part Disc brake Clutch Engine Brake
 
#21 ·
Free at last!

In the earlier link, Richard recommends the following to evaluate clearance in the VSD clutch pack, following a thorough bath (I presume the VSD, not me):

“There are openings on the bottom of the case. You can use your fingers to force the internals upward to measure clearance (Finger micrometers) With that done you have an idea of how much slack has to come out.”

Pre-cleaning, and with remaining fluid to lessen clearance, I’m just able to feel movement when using Richard‘s technique so after a bath, I presume that distance will increase. Since I want to blast the plates anyway, I’ll do minimal reassembly after plates are cleaned and recheck clearance.

Auto part Automotive tire
 
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#23 ·
“There are openings on the bottom of the case. You can use your fingers to force the internals upward to measure clearance (Finger micrometers) With that done you have an idea of how much slack has to come out.”
Richard also helped me with my measurements. It took a bit to understand, but once it sunk in, it was pretty easy. I don't have the calibrated finger micrometers that he has, so I thought I better use some measuring tools.

Firstly, before you remove those bolts, mark the position of the assembly.
Auto part Clutch part Gear Rotor Clutch


Using a digital caliper, measure the depth of the ridge on the cap (I don't know what that is called, but you get it I hope :) )
Crankset Bicycle drivetrain part Bicycle part Rim Blade


Zero out the digital caliper and measure the depth of LSD assembly.
Auto part Bicycle part Crankset Rim Wheel


My clearance is 0.0055". According to Richard:

"The measurement of the inside of the housing should be about .010-.016" (dry) for a 2 disk, and .014 to .020" for a 4 disk, larger than the top plate`s thickness.
In both the smaller number is fine for street use and the larger clearance for track use."

Auto part Wheel Transmission part Machine Bearing


Hope that helps.

Good luck,

Vin
 
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#22 ·
I took a moment to see if bolts on the LSD would break loose and now understand why Richard advised using an impact wrench to loosen them. No air in my tank (and no compressor) so that will wait for another day.

The unit has been sitting on its end since removal and when I first checked for movement, as described earlier, I did feel some play. An attempt this time, and no go.

There was a puddle of Red Line’s finest under the LSD so maybe that had something to do with the lack of movement.

The gear oil I drained earlier was dark and only had a few hundred miles on it, so will disassemble soon and inspect the plates.
 
#24 ·
Hey Vin,

You are a treasure and valuable contributor to our Forum!

Many thanks.

“Pictures, we luv pictures!”

A micrometer is not within my bag of tricks, so sourcing one will be my next task.

Skiing at Diamond Peak is on today’s schedule.

Best
 
#25 ·
I am glad to be able to help. I love pictures too!

The digital caliper is easily found. Here is a link to Harbor Freight if you have one near you. $20. It's a tool, that once you have, you will use it often.


Skiing on a Monday, love it! Hills must be empty :)

Good luck,

Vin
 
#26 ·
Harbor Freight is my go-to tool supplier! Got me through my LB7 injector job a few months back! If I were a pro, a different story, but their goods work for me!

”Skiing on a Monday, love it! Hills must be empty :)

MLK Day may effect that situation, but skis are waxed and I missed last year.
 
#28 ·
Thanks Richard and yes, I did put it back together.

This was just for the OP of this thread and future reference.

Thank you as always,

Vin
 
#30 ·
Hey triz!

Get your own thread! :) :) :)

No gasket on mine, but a lip which extends total contact area to near 3/4”.

Fasteners are secured with a locking tab, so if properly torqued, unlikely retorque will help, but only option.

Drip pan?:)

Richard:

“If your measurement of .005" clearance was accurate on dry clean plates just put it back together.”

What about your advice to recondition plate surfaces with blasting?
 
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