This is the second time I have done work on the final drive so I would like to think that I know what I am doing. The first time was when I swapped in a 3.9 FD and kept the stock VLSD. I followed the FSM precisely and everything was fine for ~20k miles.

Now that I am turbo, I am re-installing the stock 3.53 gears and a Quaife QDF13L. I just sent an email to Quaife technical support but I wanted to solicit opinions on there while I wait for a response.

My question pertains to runout. When I first bolted the ring gear to the differential and installed it into the housing, the runout on the 45 degree chamfered edge of the gear measured about .0025". Nissan specifies a limit of .0020" so I removed the differential, unbolted the ring gear and rotated it 180 degrees and tried again. This time the runout measures ~.0045". I noticed that before the bolts are installed, the ring gear has about .005" of radial clearance to the differential itself. This seems like a lot, and I don't see how the runout is ever going to be within .002" without a lot of trial and error when bolting the ring gear on or somehow trying to shim the ID of the ring gear to hold it concentric with the diff when tightening the bolts. Is this normal? Should I just keep unbolting and re-bolting the ring gear until I get lucky??

Also I took 10 backlash measurements around the gear and they vary by a total of about .002" from max to min, which I believe is a result of the excessive runout.

Tomorrow I am going to slide the ring gear back onto the stock VLSD and see how much radial clearance there is, just for comparison. I don't recall the ring gear having as much play on the stock VLSD.

 

I went through the same damn thing on my Quaife too! I thought I was being stupid and asking alot of questions because it was my first rear end and it was the only thing I was not prepared for during my research before I bought it. I talked to drag racing buddies, machinists at work etc. and they never noticed a problem on anything they ever worked on. Most web sites in general terms say you may need to help a ring gear onto a carrier with a few light blows with a rubber mallet! - I wish! Searched Google every night for a week! I think mine was also at least 0.005" play and the first time I bolted it up and got to the point of checking is was maybe 0.007" runout! Once I unbolted it the amount that the ring moves on the carrier is quite a bit if you pay attention to it.
I think I posted all my begging for help here in the sticky 4.083 gears thread starting with post #799 on up...
https://my350z.com/forum/engine-and-...talled-16.html
I contacted Quaife too, measured other Nissan ring gears, etc. - I think it's all written down in my posts. I believe it is the Quaife itself as evidenced by your comments on all of the OEM parts - but! you cannot say that the Quaife is out of tolerance OR that you cannot ignore the fact that you have to account for manufacturing tolerances so every ring gear will fit. Don't know how OEM appears so centered/tight. The one factory gearset I have looks very tight in the middle also. After debating about it for a week or two, what I did was center the ring gear with plastic shim in between the carrier and the gear in the center. Then torque all of the ring gear bolts to the high end of the torque specs. and hope it never moves. Take the shims back out! It was a little difficult to get one of the shims out because the gear is going to rotate a little during the tightening procedure. I settled on doing this after I put the Quaife in the pumkin and checked it with no ring gear installed and checked both axial and radial runout any any other points I could think of to make sure the Quaife was manufactured straight.

Couldn't find any evidence of people on other cars/brands needing to do this but 75% of the people that document builds don't seem to know what is involved with a rear end anyway. Post back here or PM me if you want me to try and think back or lookup anything else from my mess. I've got 14,000 on mine but wouldn't know if it slipped out of center.

 

Here is the response from Quaife:

"Hello,

When we fit the differentials we always go to within 0.003" any more than this and we take the crown wheel off and go again. The .0025" would have been fine.

It a case of trail and error. You would also measure your crown wheel with a clock to make sure it is flat.


Kind regards

Dave King"

bjr - thank you for the information. After reading your post, I decided to try the shim idea. I actually used notebook paper and wrapped it around the pumpkin and then slid the ring gear down onto the flange, making sure not to get the paper stuck between the mating surfaces. Then I snugged up all the bolts and pulled out the paper. A tiny piece of paper got stuck between the id of the gear and the OD of the pumpkin but I decided to just leave it in there because I'm sure it wont hurt anything, it will probably just dissolve in the oil. After doing this, the runout was less than .002". After tightening to full torque the runout was still less than .002", so I would call it a success.

I agree it seems like Quaife could tighten up the tolerances and get it closer to the OEM pumpkin so this shimming and trial-and-error nonsense wouldn't be needed. I doubt it will move but it still doesn't give me a warm fuzzy feeling.