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OBX Differential Inspection and Installation

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I took pictures of all the measurements I took, I'll try to get them up today, but all the info you need is in that spreadsheet:

 

I would need to know:

 

1) The "assembled length" in between the flats of those two "stars" when the diff is assembled.

 

I measured the height of the stacks:

 

Full Rbryant Stack )()()()()( 0.8875

Full OBX Stack )()()()( 0.8840

 

2) The "ID" of the lip inside the "stars" that would dictate the maximum diameter of the possible spring.

 

Largest Diameter:

 

ID Washer Retainer O 1.2620

 

Smallest Diameter:

 

ID Retainer "Lip" o 1.1390

 

**edit for pictures:**

 

RBryant stack:

 

IMG_20120410_074309.jpg

 

OBX Stack:

 

IMG_20120410_075219.jpg

 

Greater ID of washer retainer [or star piece as you call it]

 

IMG_20120411_073653.jpg

 

Notice the variation from my measurement yesterday - I'd try to get something that would be right in the middle of the range between the greater ID and the lesser ID. [Maybe somewhere around 1.200?]

 

Also, JMort suggested leaving a washer in there to act as a secondary retainer for the spring if you went that route, I'm assuming to prevent the spring from accidentally coming off that retainer 'seat.'

Edited by FlatBlack

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My "Gen 2" RBRyant stack ended up looking like this:

 

()()()()

 

With a stack height of 0.7240"

 

The bolts had about 0.75-1.0 turns to full tight.

 

My threads were SUPER buggered on the lower case - I had to go buy some 50mm bolts after spending ~2 hours yesterday tapping out the holes.

 

Stock are 45mm M8x1.25, the RBryant bolts are 60mm M8x1.25. I ended up with 50mm bolts, which added 5 threads into the case. I'm using blue locktite as well.

Edited by FlatBlack

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So I'm revisiting this whole circlip issue, since on decel even after upgrading to the latest Rbryant washer stack I still get grinding on decel, and the occasional clunk. In this case, I think my slack is resolved, but my passenger side-stub is rubbing on the diff.

 

I see above that Cygnus says the circlip locations are both the same depth, so I'm thinking I might try getting another set of stub axles and running two long ones. Anybody have a donor set I could purchase?

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I'm looking into getting one of the obx units the only problem I'm having is I cant find the unit part number #10528. If someone could point me in the direction of who to buy from or where people are getting them I would be much abliged.

 

on Ebay motors, you get some choice !

 

http://motors.shop.ebay.com/i.html?_nkw=obx%20lsd&_dmpt=Motors_Car_Truck_Parts_Accessories&_fln=1&_fpos=Zip%20Code&_fspt=1&_sadis=2000&_ssov=1&_trksid=p4506.c0.m282&Make=Nissan

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So my OBX diff should arrive this week, and my rebuild kit is here already. I took a look at the FSM to see what I'm in for as far as putting it back together again and my head began to spin. I hear mention on hybridz of shimming the ring gear and checking backlash upon reassembly but that's it.  

 

What about shimming the pinion gear, side bearings for preload, and checking the pattern on the teeth? I would imagine all this can be thrown off when installing a cheap Chinese carrier, but mention of these procedures is scarce. If I can get my hands on a dial indicator, I figured I'd put it back together the way it came apart and check the back lash tooth wipe patterns. If they don't look right I supposed i could stuff my pockets with cash and head down to a driveline shop, but ideally I'd like to do it myself.

 

Am I over-thinking this, or are most people neglecting (to mention?) these crucial steps?

 

I have zero experience with diffs, and minimal experience with transmissions, but I'd at least like to try it myself before shelling the cash for someone else to do it.  

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Update: Diff has a arrived. I pulled it appart and found that 1 bolt that was about 1/2" shorter than the rest, and was stripped to hell. it also damaged the thread in the case which I attempted to retap, however the case material seems very hard (good thing I suppose) and it just stripped my tap. I thought my tap set was decent, but I supposed I'll bring it to a machine shop to have them do it. Perhaps they can check runout on the ring gear flange. It seemed Honda guys were have issues in that department, but I haven't heard of that here.

 

Also I may be crazy, but the alignment dowel in the case seemed to have magically disapeared. I swore there was one there, though I can't see it being a huge deal if it's missing.

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I too just got my OBX, which I decided to go with after reading through these threads. Haven't opened it yet, that will be the weekend project. Anyway from what I can tell through the small holes on the side that it looks like my gears are actually facing the correct way, but I'll find out once I open it up. I have the rbryant rebuild kit ready to go so this should be an interesting experience.

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Sorry to double post in this topic, but I'm past the point of editing my previous post. Anyway I'm curious how you guys judge when the case is snug? I'm in the process of doing this and basically what I'm doing is just leaving the diff on the floor and using a wrench to tighten the bolts until the point where I can't tighten the diff case bolts anymore without holding onto it/clamping it down. So every turn past this is at least now starting to register torque on my digital torque wrench. Is this a good way to judge or should I be further back?

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Hi guys, I have now installed my obx diff and I have a question for you, have anyone noticed their diffs getting louder after install, howling or whining? Mine is howling pretty loud in the 45-70kph area, disappears completely under or over that speed

Problem is I can't compare with how it was before because I have never driven with this diff. Stock I had a 3.5 installed, then I bought a zx turbo engine and driveline and put the obx in the 3.36 diff and installed it in my car just recently.

The car the diff came from had about 260-270 thousand km's on it so it's definetely got some mileage on it though....could it be a worn pinion bearing perhaps? 

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Just a thought, has anyone tried drilling out and re tapping the ring gear to accept 12mm bolts? I have a set from a s13 diff that I would like to try and use. I can think of a couple issues that slow and methodical work would fix, but any major problems I should be aware of?

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..has anyone tried drilling out and re tapping the ring gear to accept 12mm bolts? I have a set from a s13 diff....

 

short nose gear set won't work in a long nose diff housing.

Edited by Trevor

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I'm aware of that, should have clarified, the bolts I'd like to use are those from the s13 rear end, and fit the OBX better than the 280z bolts. I've done some reading, and it sounds like the ring gear is pretty tough to drill, but anybody have any success?

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I'm aware of that, should have clarified, the bolts I'd like to use are those from the s13 rear end, and fit the OBX better than the 280z bolts. I've done some reading, and it sounds like the ring gear is pretty tough to drill, but anybody have any success?

The tapped holes are in the ring gear, so you'd not only need to drill them but also blind tap them. Just run the 10mm bolts with the mcmaster.com spacer. The ring gear bolt strength isn't likely to be an issue.

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So to clerify, I have a 280zx n/a 3:90 diff in my 240z all stock axles. I bought the mc master ring gear bolt spacers, and the washer/bolt kit. is there anything else i need to finish this project?

 

does this sound right?

so i pull the stock cover off, and the axles, then remove the two half-moon shaped pieces to remove the center housing with the ring gear attached. then i remove the ring gear, and install it to the obx unit, then install it again and install those c-shaped parts and check for backlash? what steps am i missing? 

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http://forums.hybridz.org/topic/54124-step-by-step-installing-an-lsd-into-your-open-diff/?p=488661

 

Warning! The OBX apparently isn't machined to the same tolerances as the Nissan stuff so most people ARE having to adjust the backlash. Not a big deal to do that, but the writeup says that you probably won't.

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I can confirm what Jon just said. I put an obx in this summer and the backlash was not right. At the time I didn't have the shims to adjust it, but if I switched the shims to the opposite side it was pretty close, but not within specs. I put a couple hundred miles on it like that and it was whining pretty badly. I'm about to take it back out and shim it correctly this time. Hopefully I didn't damage anything. Maybe someone will read this and not make the same mistake I did. I wouldn't normally do something like that, but it was only a couple days to zcon and I didn't want to miss it.

 

Rob

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I just finished installing my OBX into the housing a few minutes ago. I put it in with new Timken bearings, and kept the shim alignment exactly as it came out, I'm also using an R200 out of the Z31 if that makes any difference so I didn't need the spacers for the ring gear bolts. Anyway I measured the backlash, and unless I did something wrong I was coming out at right about .006in. I didn't have the tool for when I took the diff apart, so I'm just going with the fact that it fit factory specs.

Edited by DuoWing

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So to clerify, I have a 280zx n/a 3:90 diff in my 240z all stock axles. I bought the mc master ring gear bolt spacers, and the washer/bolt kit. is there anything else i need to finish this project?

 

does this sound right?

so i pull the stock cover off, and the axles, then remove the two half-moon shaped pieces to remove the center housing with the ring gear attached. then i remove the ring gear, and install it to the obx unit, then install it again and install those c-shaped parts and check for backlash? what steps am i missing? 

 

You will definitely want to replace the bellville washers and case bolts with higher quality ones from R Bryant or Mcmaster & Carr, check to make sure the gears are properly orientated, and many, including myself opt to file down any rough edges or casting flash that could break off later. All of this is covered earlier in the thread. You will have to press carrier bearings onto the OBX case, removing the old inner races intact can be tricky, but if you are able to order straight from the bearing manufacturer, the bearings are very cheap to replace (think I paid about $12/ea straight from SKF). When it's back together, check back lash and shim accordingly, and finally check the gear wipe pattern. This might be best done at a driveline shop if you don't have the tools and a collection of shims. I paid about $150 to have it done. 

Edited by m1ghtymaxXx

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Do these obx units not have axle circlips in them? This is something that I didn't realize when assembling the obx and now I can't seem to pop the axle shafts into the diff and get them to lock in. Anyway, I managed to pull the circlips out of the old diff. Now I have no clue how to compress and install them into the new one. Any tips? I tried to put one in an attempt, ended up managing to mangle up the clip and get it back out. Are there any generic ones that have the eyelets that can be used?

Edited by DuoWing

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I did a very similar thing when I installed the obx in my car. This is the thread on here that describes how I got them in without taking the diff apart. I did it with the diff installed in the car.

 

http://forums.hybridz.org/topic/114145-what-happens-if-you-dont-install-retaining-clips-for-280zxt-cv-axles/

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