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OBX Differential Inspection and Installation


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  • 4 weeks later...
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Iinstalled an OBX into my Datsun R200 diff. The washers failed after only 4 hours of track testing. They were essentially flattened. We were not aware of the reversed gear trick (just found this thread today), and replaced the washers with a heavy coil spring. We have only driven it on the street a few kilometres since, but it seems to work. Will see if it lasts any longer than the original washers...

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  • 1 month later...

All,

 

I just wanted to add a note that I have been shipping kits with two different diameter washers for a few months now with very good success.

 

The big problem I have had with the R200 OBX LSD was that there is a large space between the center washer retainers which can allow for the washers to slip outside of it and then misalign.

 

Picture this: [)()()()(] If the () washers in the center aren't surrounded by the edges of the retainer and there is space for them to move then they will....

 

The solution is this:

 

[)()()(]

 

 

I ship 4 larger washers that go in the center so that they keep everything aligned. The larger washers are actually retained by the diff case its self instead of the washer retainers. They also cup around the smaller washers so that they hold the smaller washers in place. I took care to make sure that they are very close to the same spring rate as the smaller washers. (because they are larger they have to be thicker too)

 

I have been shipping 4 larger washers and 7 smaller washers. This is because the machining hasn't been that consistent and some of the LSDs require more washers. I don't expect people to require all of the washers and in most cases only 2 of the larger ones will be needed but on some of the newer units they seem to be a deeper pocket where all 4 larger washers can be used. Originally the first R200 diffs only needed about a 14mm stack of washers and I have recently heard of them being ~20mm (based on customer feedback) so that is the reason that I can't just give people a one size fits all configuration. :(

 

 

The larger center washers should only be used if they are sufficiently spaced by the outside washers to where they won't ever touch the normal washer retainers. If they compress and touch the retainers then the small washers will be loose, rattle, and not do their job.

 

If anyone has feedback on the latest kits it would be great to hear it here. I am also interested to see some pictures of your installs.

 

Thanks,

 

Rich

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I just installed the updated version of rbryant's kit and here are some pics. The gears have been reversed.

Hardware on the top is what came in the unit, hardware on the bottom is the rbryant bolt/washer kit.

 

post-4314-013276200 1291083503_thumb.jpg

 

What I found is that if I install the "new" stack )()()(, the larger washer rest on the retainer, so I stacked them like this )(()())(.

 

post-4314-067480500 1291085023_thumb.jpg

 

You can see how far the retainer sticks up with this configuration before I put the cap on. Does it look acceptable?

 

post-4314-098434400 1291085253_thumb.jpg

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  • 9 months later...

So I just took the Z out for a nice Sunday morning run and heard some bad noises. I installed obx unit described above in a rebuilt r200 3.9. Upon acceleration, everything is good, but when I let off the gas I hear some nasty grinding/rattling noises coming from the differential. Ideas? Help?!

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Anyone consider just putting a solid thick spacer in there to take up the slack? Lots of other helicals aren't preloaded at all and taking the slack out would probably eliminate all the cracking/popping noises under decel. It sounds like once the springs wear down you don't have any preload anyway.

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So I just took the Z out for a nice Sunday morning run and heard some bad noises. I installed obx unit described above in a rebuilt r200 3.9. Upon acceleration, everything is good, but when I let off the gas I hear some nasty grinding/rattling noises coming from the differential. Ideas? Help?!

 

I'm using a different LSD unit in my car but I had a very similar symptom. I had a shop install my LSD and it turned out to that the pinion nut was not torqued tight enough. This allowed the flange bolted to the driveshaft to spin at a different rate from the differential on decell and ended up grinding the splines on the flange off quite a bit before I made it back home. Pinion gear splines were still fine, but had to replace the flange. Not a hard fix, but definitely not fun.

Edited by h4nsm0l3m4n
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I'm using a different LSD unit in my car but I had a very similar symptom. I had a shop install my LSD and it turned out to that the pinion nut was not torqued tight enough. This allowed the flange bolted to the driveshaft to spin at a different rate from the differential on decell and ended up grinding the splines on the flange off quite a bit before I made it back home. Pinion gear splines were still fine, but had to replace the flange. Not a hard fix, but definitely not fun.

 

I dropped the diff out today and nothing is obvious, the pinion flange seems to be good and tight. When I look through the center of the diff, the washers still look ok. Not sure what's going on, so I am going to run it by East Coast Gear Supply in Raleigh to see what they say. I'm also going to see if they have a solution to the washers, as in a solid spacer what JMortensen is talking about.

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  • 2 months later...
  • 2 months later...

Sorry to resurrect this old thread, but I'm having some issues installing the OBX LSD into my '75 280z's stock open R200.

 

I rebuilt the OBX using the instructions posted here with rbryant's deluxe kit. I did not have to swap gears but I did flip over the top gear to ensure BOTH c-clip grooves were toward the center/inside of the case. Sent it with my R200 diff to a reputable shop that even specializes in Z cars. The owner has installed many other carriers including Quaifes but not the OBX. He installed fresh carrier bearings and c-clips from Nissan, but he tells me that although one of my stock stub axles snaps into the OBX just fine, the other side was too short to engage, but the 300zxt CV shaft snaps right in.

 

First of all, I've searched and searched but I've never heard of the stock 280z stub axles not fitting the OBX. Secondly, both sun gears should be identical so I couldn't have them reversed. Thirdly, why do 300zx CV shafts fit fine? I thought they had similar tolerances, but is the c-clip groove on those closer to the tip??

 

I was prepared for the easy task of rebuilding the OBX, but I wasn't prepared for this complication...anybody got any ideas? I feel like my mechanic and I may be missing something simple...and the first autocross of the season is coming up in less than 30 days! Please help!

 

-Chris

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Just to rule out the obvious, I would double check the part number of the OBX unit to make sure it is correct. This is the first I have heard of this problem, I know mine lock in tight with the stock 280zx stubs. But with the halfshafts bolted to them, it scrapes the housing upon deceleration because of the play in the worm gears. The sun gears are identical but have to be oriented opposite of each other for the c clip grooves which it sounds like you did. Does you mechanic accidentally have the stubs mixed up? Is the groove clear and straight on the stock 280z stubs? I know these are obvious questions but possibly overlooked?

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Tank, I searched by part number before ordering and I *think* I recall verifying the part number on the box when it arrived, but I'll have to wait 'til Monday to check the part number on the actual unit itself to be sure...

 

And Jon, I was not aware of that slight 3/8" difference in length of the stub axles. I knew the halfshaft lengths were different, but I personally thought the stubs were symmetrical. Not sure if my mechanic is aware of this difference, but I think that might explain our problem. I'll be crossing my fingers until Monday!

 

I really appreciate both of you for chiming in; I've been wracking my head trying to figure this out!

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And Jon, I was not aware of that slight 3/8" difference in length of the stub axles. I knew the halfshaft lengths were different, but I personally thought the stubs were symmetrical. Not sure if my mechanic is aware of this difference, but I think that might explain our problem. I'll be crossing my fingers until Monday!

 

You've got it backwards, all half-shafts are equal-lengths. It's the stubs which snap into the differential that are different lengths. Did this solve the issue?

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Image of the stubs easy to see the difference

OBX008.jpg

For what ever its worth my 2009 OBX install, after correcting the gear direction, crappy fasteners, using McMaster washers etc is still quieter than the stock diff ( no thumps, bumps, or gear noise) no flaws or failures to date.

Edited by John Scott
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Swapping the stubs did the trick...well, sort of. It solved the passenger side issue (shop was saying stub was too short to reach the circlip groove in the diff) but now the driver's side stub (shorter one) is engaged way too far into the diff (opposite problem).

 

Test drive was cut short by loud clunking as the heads of the halfshaft flange bolts contacted the differential case. I pried the flange out a bit and it popped into what looks like the correct position with plenty of clearance between the flange and the diff, but I don't think it's engaged with the circlip anymore, because when we noticed this problem before installation, popping that stub out to where we thought it should be left it loose enough to easily withdraw by hand.

 

I don't think this is a problem with the OBX itself, because I seem to recall a bit of play on that side as we were removing that halfshaft and I didn't check the stub for looseness after disassembly, because I thought the play might've been in the U-joints on that side...but they're solid so now I'm wondering if this was a pre-existing problem.

 

Furthermore, after popping that stub away from the diff, I now get no catch when turning the wheel by hand, BUT while doing so, I noticed some rotational play coming from WITHIN the diff; I can hear the gears clunk as I rotate the wheel forward and back as if there's play in the splines (always felt this clunk while letting off clutch before the LSD install)...is it possible the driver's side stub was replaced with the wrong part long ago and has been wrong all along!? This would explain both issues...

 

I can't even test the OBX, because I'm afraid to drive the car hard with all these potential issues...I was so excited for donuts.

 

Anyone have a hypothesis? This install isn't supposed to be this complicated!

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Were the heads of the bolts hitting the diff on accel or decel? If accel, then your gears are backwards. The side gears should move out under accel pushing the CV's away from the housing.

 

I really think someone needs to make some solid spacers for these things. Seems like you guys are having a ***** of a time with the washers (compressing washers on decel is what allows the stub to move inwards).

 

That stub needs to be clipped in. If it's not it could slide out a bit and strip the splines off. Saw a pic of that from an EVO just recently.

 

Don't attempt to figure out slop in the diff issues by turning the wheels. Not an accurate test of anything. There is slop between the side gear and all of the helicals that has to be there, and even if everything is perfect there will be a good amount of lash in there.

Edited by JMortensen
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