I have been rebuilding my differential for the last couple of evenings.  It is a "K" R180 from the front of a Nissan 4X4 truck.  From running it in my 240z, I know it was in good condition before disassembly.  And, when I took it apart, I checked backlash and it was within spec.  So, I don't believe it ever had been apart before.
 

I purchased a Quaife LSD for it.  I also purchased all new bearings and seals.  

For the differential case and the drive pinion shaft, I was very careful to install races and the tapered bearings, fully seating them in their correct positions.  I also was sure to use the spacers and shims that were removed back in their original locations.

Using old bearing as an installation tool for the front pinion bearing.

Using a homemade tool to hold the pinion from turning while setting the torque to 135 ft-lbs (factory manual specifies 122.9 -144.6 ft-lbs_

 

To get the Quaife in the case, it was required to "Fettle":

 

 

It took a lot of fettling, but I very carefully ground only where needed until the carrier just fit. In fact, I had to leave one of the main gear bolts off until the carrier was partly in the case, and then torque that last bolt through the side axle opening.  This fettling was an unpleasant surprise that added 4 hours of time to grind on the case.  I had to be extremely careful with packing the case cavity and other preparation to keep the metal shavings from the carrier and from installed pinion shaft (and bearings).

At this point, and here is where I stopped, I have installed the side retainers, left and right, with their respective shims in their original positions, with the 5 bolts on each just snugged down, not torqued.

 

 

Now, I could use some guidance.  

What I have not done that I may need to:

• I didn't measure the amount of turning force on the pinion shaft.  I don't have a suitable tool to measure that.  I see that this is supposed to be done without the pinion seal installed.  I have already installed that.  There is preload on the pinion bearings - I can tell by rotating the shaft by hand.  I just don't know how much.
• I did not remove the fresh paint (and primer) from the sides of the case where the side retainers seat.  I am wondering if those thousandths of an inch matter.  Given the side retainer shims originally used are quite thin, paint in this location may be an issue?
• I didn't measure the amount of main gear backlash with a dial gauge yet.  I just moved the main gear by hand back and forth.  Doing so, the amount of movement is noticeable.  I'd guess .015" to .020".  

I do have a dial gauge and magnetic base and plan to measure the back lash when I pick back up on this.  

I was hoping, perhaps naively, that I would be able to use the existing pinion and side retainer shims even with replacing the stock carrier with the Quaife LSD unit, but it looks like I have more work ahead of me.  The factory shop manual is difficult to understand, and I don't have the factory tools being referenced.  

Anyone have any guidance on how to proceed?  

I am thinking about buying the tool to check pinion turning force.  I am thinking to not removing the pinion seal, because I would likely destroy it in the process, but instead just factor in 1-2 additional inch-lbs into the reading I measure from having that in place.  So, if I measure 2 inch-lbs more than the factory upper limit, I'd call that good, for example.  

I am also thinking about removing the paint from under the side retainers and reinstalling them with fasteners torqued to spec to check the main gear lash measurement.  From there, I may need to order various side shims and attempt to get back lash correct?  Then check the gear mesh pattern to see if everything is set up the way it should be?

 

 

Edited September 15, 20231 yr by inline6

I put in a custom made shim today.  Instead of .126" thick, this one is .151" thick.  So, this custom one is .025" thicker.  Where the original side shims were a .3 mm on the left and a .4 mm plus a .5 mm on the right, now I have a .2 mm on the left and two .5 mm on the right.   The backlash before I took the differential apart was .005".  The backlash is now .0055"

Here are pics of the wipe patterns:

    

    

    

    

I actually don't know if these are good wipe patterns.  I mean, I have seen these pictures in the Nissan differential service guide.  But I don't know how closely the wipe patterns are supposed to match the illustrations, and for some reason the guide doesn't have illustrations for the coast side:
 

 

 

 

 

Edited June 30, 2024Jun 30 by inline6

I used to have trouble trying to figure out what the various diagrams were saying.  Then I summed it all up as - "any contact mark pattern that does not overlap an edge is good".  Basically, if you can see all of the contact point on the face of the tooth, it's fine.  Doesn't have to be in the middle.  Just has to be off of any edge.

I thought about it some.  Since I have a stock differential, I thought I would get a wipe pattern from it to compare.  I measured backlash at just under .010".  This is a few thousandths more than specification. 

    

    

 

These are very different.  The size of the surface area where the paint is displaced is much larger.  

These pics look more like my first effort to get a wipe pattern with just the .126" shim in place where I had way too much backlash:

  

I am kind of lost now as to how to proceed.  I am going to run back through pics from prior efforts and stew on this.

 

 

 

Edited June 29, 2024Jun 29 by inline6

I've been staring at my posts and pictures for hours.  I watched some more Youtube videos.  Going to jot down my thoughts and sleep on it.  

The wipe patterns I have been getting are not right.  They have a sharp edge on the bottom.  They are too far down into the base of the tooth.  The contact area should be larger.  It should be centered, both between the base and top of the tooth, as well as centered between the heel and toe of the tooth.  Drive side matters most.  So, I need to center the contact on the drive side.  

I have been chasing too hard after the backlash.  By adding pinion shim thickness, I have been able to reduce backlash, but I sacrificed pinion to crown gear alignment.  The pinion is now too "high".  I will have to reduce the thickness of the pinion shim. 

My first wipe patterns- I believe these resulted with the .126" pinion shim and the side shims in their original locations - which means this was with about .020" of backlash, and I hadn't figured out that I had to put some drag on the carrier to make the wipe impression more defined:

  

No hard edges... and what appears to be much more surface area of contact.  Same set up, but teeth that were not painted, but received paint transfer:

  

Again, no drag applied to the carrier to help the impression.  

.020" backlash is too much... for sure.  I'd like to try putting the .126" shim back in and moving the side shims to the right side... and doing a wipe pattern while applying drag on the carrier.  If the wipe pattern is similar to the above in that the surface area of contact is larger... that will be good. Unfortunately, I will not have any further backlash adjustment.  At that point, to tighten the lash, I will need to explore using shim stock between the crown gear and the Quaife carrier assembly.

 

 

New gears and used gears will have different wipe patterns.  That said, my 4.11 gear set is used.  I should have taken a wipe pattern before I took it apart.  Had I done so, that would be the reference I could be using now.  

I am going to assume that my 4.11 gear set should have a wipe pattern more like that of the stock diff I posted pics of yesterday, and attempt to start again with the .126" stock shim in place, but start altering the ring gear position to reduce the backlash.  I'll see where that takes me on this trip of experimentation with wipe patterns.

 

Update time.  I put the stock pinion spacer/shim back in and took a fresh set of wipe patterns.

 

These wipe patterns look "better" to me in that the amount of surface area where the paint has been "cleared" is much larger that what I was achieving by adding thickness at the pinion spacer/shim location. 

This time I put drag on the crown wheel as a rotated the assembly to get the marks.  With the .3 mm shim on the left side bearing and the .4 mm and .5 mm shims stacked on the right side bearing, I measured .021" plus some of backlash.  The pattern above was with that combination.  

I moved the .3 mm shim to the right side and measured backlash again.  This time it was .012".  I somehow forgot to get a wipe pattern after doing so.  I will do that and take some more pics and post them here.  With less backlash, the wipe mark should move further away from the heel end and toward the toe end (on the drive side of the tooth).

With no more shims to move from the left to the right, the best way I can think of to less the backlash is to machine the left side bearing retainer.  A picture:
 

 

 

Removing material from this face will result a change to the the carrier bearing location vs. where it sits now when the flange is bolted to the case.  

So, to fix the excessive back lash, I want to shift the carrier to the right some small number of thousandths of an inch and I want to achieve this by removing a small amount of material from the left side flange.  Doing that will bring the ring gear closer to the pinion gear.  Additionally, whatever amount is removed from this retainer has to be matched in additional shim thickness on the right side bearing retainer so that the preload on the carrier bearings does not change.  

As originally assembled with the original carrier, there was a .3 mm (0.0118") on the left and a .4 mm (0.0157") and a .5 mm (0.0197") on the right. That combination adds up 1.2 mm.  Side shims are sold in the following mm sizes: .2, .25, .3, .4 .5. 

If, for example, I estimate I can get the backlash within specification by removing .2 mm = 0.00787" from the left side flange, then that amount would be removed from the left side flange and I would add a .2 mm shim to the existing stack of shims on the right.  Or, another option which would achieve the same thing would be to machine .5 mm off of the left retainer, and then add a .3 mm shim to the left side and a .2 mm shim to the shims already on the right side (add .2 mm more to the .3 mm, .4 mm, and .5 mm shims).  Again, whatever the amount that gets machined off of the left side retainer, I will need to add back into the total shim thickness.  

Ultimately, I need to get backlash to .004"-.008".  It may be best to remove .5 mm from the left side retainer because then I have many sizes of shims to work with from an adjustment standpoint.  Also, removing .5 mm covers the possibility that I run into a problem of removing .2 mm and that not being enough to get the backlash to .008" or below.

 

Edited September 4, 2024Sep 4 by inline6

Ok, I am back at this thing!  I sent the left side flange off to have .5 mm removed by lathe operation from the area indicated in the picture in the prior post.  Tonight I found the time to mock things back up again and check backlash.  

With .5 mm removed, I put a .3 mm shim on the left side.  Thus, I added a .2 mm shim to the existing set of shims on the right side flange (.3 mm .4 mm and .5 mm).  In theory, the distance between the bearing races of the left and right side flanges is what it was before the lathe turning, though I suppose it could be a few "tenths" of thousands different.  I don't think I can know for sure.

Assembling and then measuring backlash as I have done before, I got .005" of backlash.  Hallelujah! 

I did a quick and dirty version of checking the wipe pattern and it looks good to me.  I will post pictures of that a bit later.  One thing I did check and find out though is that while the Quaife unit has no measurable runout (checking with a dial gauge (units in .001") on the part of the carrier unit the crown gear bolts to, the same cannot be said for the crown gear.  I ran the dial gauge against the gear and measured a bit more than .004" of run out.  I am going to loosen the crown gear bolts and try to adjust that so it is within specification (.0031").  

Stay tuned!

 

Sounds good so far.

13 hours ago, inline6 said:

I ran the dial gauge against the gear and measured a bit more than .004" of run out.

As for the runout on the gear, the first thing I would do is look everything over under magnification and look for burrs / kicked up material (or anything else) that is interfering with the positioning. Maybe you'll get lucky and find something that can be easily dressed off or cleaned up to make things better.

Isn't the ring gear located by an interference fit on the center of the carrier?  There shouldn't be any play to play with.

I was measuring runout incorrectly.  I was measuring on the outside, angled edge of the crown gear.  When I measured the backside of the gear, I got less than the .0031" factory specification.  So, here are the wipe pattern pics:

Drive side - first pic is directly painted teeth, second pic is the paint transfer to clean teeth.  

  

What I see here is that the contact area is nearly centered both from a top and bottom of the tooth and toe and heel of the tooth.  The total surface area of the exposed metal (exposed by paint displacement) is much greater than my prior efforts where I was changing the pinion shim thickness.  Paint is still present on the tooth surface above and below the exposed metal... and on the toe and heel of the tooth as well.  This looks very good to me.

Shifting now to the coast side of the gear:

  

 

This is not as ideal.  The exposed metal is mostly on the toe side of the tooth.  It almost runs off the toe edge.  However, I see a little bit of paint on the toe edge.  And the surface area of exposed metal is quite wide and centered top to bottom on the tooth.  I'd like to see the exposed metal area shifted more toward the center (with reference to the toe and heel) of the tooth.  

Looking now at teeth that were not painted:

    

 

The pics above show paint that was transferred from the pinion gear to "clean" teeth.  In these pictures it looks like the contact area is a bit more extensive.  The width of the contact from top to bottom of the tooth is quite large.  And the exposed area of contact appears to cover about 1/2" of the tooth between the toe and heel, mostly on the toe side.  

I am happy with the results I have achieved here.  So, I will proceed with installing the oil seals and installing it in the car.  It will be interesting to see how much noise this differential makes.  From when I had it installed previously, I recall it made a low but noticeable amount of noise on deceleration, but it was quiet when under load.  I had a 3.9 in the same car for a bit and it was incredibly quiet.  I sold that one some time ago though as it wasn't the ratio that I needed.

Net/net (summarizing this thread), I have installed the Quaife LSD carrier.  I have replaced all of the bearings in the differential.  I have reused the existing pinion shim and pinion spacer.  In order to get the backlash within specification, I had to get the left side bearing retainer turned in a lathe to remove .5 mm of material, so that the retainer could recess that amount more inside the left side of the differential (when differential is viewed from the back).  The .5 mm (about .020") which was removed was "replaced" with shims.  I added back a .3 mm (.1181") shim to the left side bearing retainer, and put a .2 mm (.00787") on the right side bearing retainer with the rest of the shim stack there.  

It would seem that replacing bearings on the pinion with new ones was actually "no big deal" with regard to changes to the pinion and ring gear meshing.  Swapping in the Quaife carrier caused the ring gear to move away from the pinion gear vs. the stock carrier.  Also, replacing the side bearings in the side retainers did not appear to change the relationship of the carrier to the case either.  I am confident in this because I checked the bearing preload on the side bearings at one point - the pinion gear was not installed, and I installed the carrier and checked rotation of the carrier.  My check wasn't measured with tools, but by hand; however, the preload "felt" noticeable, but not "heavy". 

Anyway, I think I landed in a good place.  I will be able to test that out now when I install the differential.   

 

Edited September 7, 2024Sep 7 by inline6