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OBX Differential Inspection and Installation

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The OBX does not come with circlips. I was aware of this when I was installing mine so after several hours I managed to wrestle them out of the old carrier by slipping a bunch small (jewler's) slotted screwdrivers around the the clips to compress them and pop them out. Installing them in the OBX side gears was a bit easier, but still a struggle. I think I was able to install them once I had slightly bent them to a smaller diameter. I was nervous they might not want to let go of axles so I filed down the beveled groove on the stub axles slightly thinking it should help the axle slip out of the circlip a bit easier when needed. No issues so far. 

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Seeing as doing this was the first time I ever disassembled a differential I didn't realize about the clips. I could see how it would be much easier to pop the circlip in with the OBX unit assembled, but I've even found a thread where a guy didn't have the clips in his Quaife. Anyway I've ordered some new clips, I mangled the 2 clips that came out of the open carrier in the 300zx that I installed the OBX into, I could still try and pull the clips from my open from my 280z, but I would like to keep that diff as a backup incase the OBX grenades or something.

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Alright well it's finally together, after waiting almost a week and a half for those circlips, I got them in thanks to the instructions from you guys. Axle flange, or whatever you call those pieces clipped in nicely. I didn't encounter any issues with clearance between the case and the backside of the flange. I also had no issues with backlash. I wonder if the clearance issues people encountered came from the carrier needed to be shimmed differently? Also I didn't really see anyone mention it, but I did notice that the shaft part of the flange is longer on one side. So I don't know if the shorter one can be popped into the side that has the larger shim on it, maybe this could cause the clearance issue? Also I don't know how this could potentially affect someone who maybe needs to shim their carrier differently from stock?

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After 3 seasons one of the large Belleville washers disintegrated and filled my diff with metal shavings. After a teardown and inspection it seems everything is okay except for a some slightly bent and chipped teeth on the helical gears inside the LSD unit. My plan of attack is to grind down any high spots on the gears, (possibly even weld up and grind down low spots too), then reassemble the carrier and give it to a local driveline shop and have them pull the pinion shaft, thoroughly clean the case and reassemble everything using new pinion bearings and reusing the carrier bearings and shims which seem to have survived unscathed.

 

I have 2 questions. First is regarding replacing the Belleville washers. I used the Rbryant washer and bolt kit at first assembly and even the quality replacement washers failed catastrophically. Did anyone every find a coil spring that fits, or anything other alternative solution to the Belleville washers for gear preload?

 

Since replacing the washers is likely the only solution, I've been looking to source them from my local Fastenall branch (McMaster and Carr doesn't sell personal orders to Canada). The RBryant kit comes with a pair of 35mm washers that go in the centre of the stack in between the sun gears to hold the remaining 31.5mm washers in place. I measured the indside diameter of the large helical gears to be about 36.4mm to the inside of the teeth, yet Fastenall only caries 34.036mm OD washers. It seems to me that might be a tad on the loose side. Thoughts?

 

Secondly, as far as replacing the pinion bearings, should I be alright reusing the existing shims? I'll be using quality SKF bearings as replacement, I'm not sure if bearing replacing typically warrants reshimming or if that's more so when replacing the pinion gear and setting its height.

 

Knowing that the quality washers are still prone to failure makes me a little nervous about this diff. I'm wondering if I should be replacing the washers every second season as preventive maintenance or something. The first sign of trouble was the sound of the stub axle studs grinding on the case but I though it was just the washer stack flattening out. The last time I drove the car before pulling the diff it was making some terrible banging noises when pulling a U turn, no doubt that was washer fragments beint forced through the helical gears.

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Yes, the pinion depth spacers should be the same, because bearings are precision machined and should be the same size.

 

I still like the idea of a blank to fit into the bottom of the holes. Just a piece of steel to take up that space. I'd make it so that there is just a little bit of end play, like .010" or so. I don't think the preload is that important, and there are similar LSD's (trutrac) which run just fine without any preload at all.

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I found this site that has a good selection of springs that may be suitable in place of washer stack, here's a chart of potentially suitable spring sizes.

 

The same site sells belleville washers also so I was thinking of putting in an order for new washers and a spring and test fitting both.

 

I think one of the main issues with the belleville washers is that each side of the stack spins in opposite directions and the washers wear against each other giving them a sharpened edge,  and if one cracks, all that friction must tear it to shreds such as the case of one of my large washers. 

 

Any thoughts on how to reduce wear in the spring and spur gears it will inevitable spin against? I was thinking it may be wise to put a washer each end of the spring as a sacrificial wear piece, as long is it doesn't wear to the point of disintegrating. 

 

 

Any thoughts?

 

After a closer look at the table, I'm thinking of going with the one at the bottom of the table, part # LC 095N 01 M mainly because it has the highest spring rate. Full specs are: 

Part Number clear.gif
LC 095N 01 M Outside Diameter 30.937 mm Hole Diameter 31.750 mm Wire Diameter 2.413 mm Load At Solid Length 142.513 N Free Length 22.224 mm Rate 10.43 N/mm Solid Length 8.559 mm Rod Diameter 25.196 mm Number of Coils 1.4 Total Coils 3.4 Finish ZINC PLATE AND BAKE PER ASTM B633 Material MW

post-1936-0-28188200-1461600403_thumb.png

Edited by m1ghtymaxXx

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Im going to remove mine SOON because of axle slop issues. I am thinking along the same lines as mightymaxx on this one a die spring would be ideal with a hardened washer on the ends. Im working with a local engineering/machine shop that know there stuff to locate a spring that will fill the void and have around 200lb or higher spring rate with in a 3mm compression. 

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Im going to remove mine SOON because of axle slop issues. I am thinking along the same lines as mightymaxx on this one a die spring would be ideal with a hardened washer on the ends. Im working with a local engineering/machine shop that know there stuff to locate a spring that will fill the void and have around 200lb or higher spring rate with in a 3mm compression. 

Can you post the part number if you find a spring that will do the job? There are a lot of OBX owners that might benefit from this.

Thanks

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