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TrumpetRhapsody

OBX Differential Inspection and Installation

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What follows are my experiences with the OBX unit (part number LSD10528). I still suggest you read through the related threads (HERE and HERE), as they give a more complete overview of the issues/solutions. This writeup is also not in "install" order, so be sure to read through it completely before starting, so you don't miss a step. Additional pictorial guidance can be found on rbryant's writeup.

 

________________________________________________________________

 

 

First thing of note is that due to a copyright issue (assumed?) all of the gears are installed backwards in comparison to the quaife. This causes the axle gears to slam into the bellville washers on accel, presumably causing premature wear and failure.

 

Here is an illustration of the difference, (pic via batou)

obx_gears.JPG

 

Be sure when swapping all the gears around that BOTH axle circlip grooves are toward the inside of the case. This will ensure both axles will clip in properly.

 

________________________________________________________________

 

 

Second thing of note is the poor quality of the stock bellevelle washers and stock casing bolts. The combination of bolt stretching and the breaking of washers has been known to lead to premature failure in these units.

 

The solution is to replace these parts. rbryant sells replacement bolts and washers as a package HERE, or you can source your own or reuse the case bolts and get new bellevelle washers HERE.

 

The actual orientation of the washers IS NOT as important as the final preload once you get everything put back together. The machining tolerances of these units make it impossible to suggest a universal washer orientation. The best advice is to try one, test it, rinse repeat until you get the proper amount of preload. Suggestions for various orientations are littered throughout the two linked OBX threads, so find the one that works best for you.

 

A good way to quickly estimate the preload is by counting the number of turns on the case bolts. From rbryant's writeup:

The overall goal with the washers is that they get ~.8-1.5mm of preload. The bolts are a 1.25mm pitch so you can tell the preload based on the number of turns on the bolts. From the time that the washers become snug to the time when the case is fully clamped by counting turns on the bolt. One full turn is 1.25mm. This means we want .5 to 1.25 turns from when the washers start to compress until the case is fully clamped down.

Rbryant's original writeup suggestion for the R200 washer orientation DID NOT work for me, so again, measure your preload and pick your own orientation.

 

Examples of McMaster washer orientations:

John Scott - ())()(()

lbhsbZ - ((()()))

cygnusx1 - ()()(())

EMWHYROHEN - ))))((((

Stock Quaife - )()()()(

 

Examples of rbryant washer orientations:

())(() - (originally suggested)

)(())( - (what I ended up using)()()()

)()()(

 

________________________________________________________________

 

 

Also, if using a S30 or S130 ring gear, it will use the 10mm ring gear bolts. Some have said it is a good idea to use these spacers (10 needed) to take up the slack in the bolt hole, which was designed for 12mm bolts. If using a 300zx ring gear, it will use the 12mm ring gear bolts, and the spacers will not be necessary.

 

________________________________________________________________

 

 

All other steps pertaining to installing this LSD can be found in your FSM, as it is just like installing any other open carrier. Hopefully you can re-use your stock carrier bearings, as I couldn't find them anywhere for less than $60 EACH.

 

For ease I will include a few important items below.

 

Necessary Specs

Suggested backlash: 0.0051"-0.0071" in

10mm Ring gear bolt torque: 43-51 ft/lbs

12mm Ring gear bolt torque: 65-72 ft/lbs

Carrier main cap bolt torque: 65-72 ft/lbs

OBX case bolt torque: 30-36 ft/lbs

Breakaway torque: ~10-15 ft/lbs (.5-1.25 case bolt turns from snug to clamped)

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Guest TurboHatch   
Guest TurboHatch

very nice write up, however one bit of required info is needed that is also missing from all the other threads and that is if you use the spacers exactly how long do they need to be cut to as to not interfere with the clamping of the ring gear to the carrier?

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nimeton    0

Hi, little confirmation. This is OBX unit part number LSD10528 is unit that will fit to R200 240SX 240Z 300ZX and old -75 280Z R200 differential? Correct?

 

 

Edit, yes I know that this will fit to R200 240SX 240Z 300ZX but I haven´t find complete certainty that this fit to that old long nose R200?

Edited by nimeton

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FlatBlack    17

Hi, little confirmation. This is OBX unit part number LSD10528 is unit that will fit to R200 240SX 240Z 300ZX and old -75 280Z R200 differential? Correct?

 

 

It's in the first sentence. unamusednew.jpg

 

What follows are my experiences with the OBX unit (part number LSD10528).

Edited by flatblack280

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FlatBlack    17

From the following thread from clubRSX, the gears are reversed from what you have stated. Is this because the LSD is mounted the opposite way in the RSX?

 

 

From: http://forums.clubrsx.com/showthread.php?t=520556

 

Dscn2782.jpg

Dscn2780.jpg

 

 

Maybe because they take the ring gear side off to inspect theirs, and we take off the top side opposite the ring gear?

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cygnusx1    12

It actually depends on the application.  It depends on which way the torque is being applied to the ring gear by the pinion.  The bottom line is that when the car is being thrust forwards, the torque on the ring gear should be forcing the left and right barrel gears away from eachother.  FWD and RWD may require opposite gear arrangements.  If you are putting it in a Z, go with our diagram.  

Edited by cygnusx1

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Marc280    0

I just pulled open my OBX unit last night and the gears were the wrong way around, so it would seem that it is definitely worth checking this. All of the bolts that came with mine were marked as grade 12.9 alhtough I swapped them out for new bolts to be sure that they are quality items. I also swapped the washers with some from RBryant as the quality of the washers does seem pretty poor (you could feel the burrs on the edges of all the washers).

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I am disassembling my OBS HLSD as I'm typing this over at Chris'[TrumpetRhapsody] house.

 

My gears were installed the 'wrong' way, and my washer stack looked like this:

 

()()(())

 

*edit* Crap >_< This is FlatBlack BTW

 

The washer stack suggested on RBryant's website is )()()( [silver, bigger OD washers in bold]

 

The silver washers bottomed out on the retainers. After some trial and error, I am using all 7 black washers as ()()()())

Edited by TrumpetRhapsody

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jc8587    0

It actually depends on the application.  It depends on which way the torque is being applied to the ring gear by the pinion.  The bottom line is that when the car is being thrust forwards, the torque on the ring gear should be forcing the left and right barrel gears away from eachother.  FWD and RWD may require opposite gear arrangements.  If you are putting it in a Z, go with our diagram.  

 

 

Actually its going in my Subaru WRX 5MT.

 

Can you explain an easy way to tell where the force will be appled to the barrel gears?

 

Thanks.

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FlatBlack    17

Actually its going in my Subaru WRX 5MT.

 

Can you explain an easy way to tell where the force will be appled to the barrel gears?

 

Thanks.

 

I've never opened up a 5MT, try to find some pictures of one open through google or whatever.

 

Look at what side of the diff the ring gear is on as it sits in the tranny. You know which way the axles turn on acceleration, so that should be pretty easy to figure out once you figure out how that thing sits in there.

 

Good luck. Once again, please post pictures as I'll be doing that to my Impreza after it gets MegaSkeet and a WRX terbeaux setup.

 

Pictures!!

 

This table should look familiar :D

 

IMG_0203.jpg

 

The "deluxe" upgrade kit. I got the washers, bolts, and 10mm to 12mm sleeves for the ring gear.

 

IMG_0204.jpg

 

It comes with seven [7] smaller, black washers, and two [2] larger, silver 'retainer' washers.

 

IMG_0205.jpg

 

WRONG!!

 

IMG_0206.jpg

 

This was the washer stack that came with my OBX. Order is listed above in my post under TR's name

 

IMG_0208.jpg

 

After flipping the gears

 

IMG_0212.jpg

 

New washer stack. I ended up using all 7 smaller, black washers, as well as the 2 silver, larger washers.

 

IMG_0216.jpg

Edited by flatblack280

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FlatBlack    17

FYI, here is my correspondence with Rich [RBryant]:

 

Mat,

 

I was having trouble with many of the differentials where the center retainers weren't fully surrounding the washer stack.

 

When that happened the center two washers could missalign and cause the stack to collapse. I tried to make a stack that contained the washers by using them ())(() but I had to use thicker than normal washers and the stack was a little too short. In order to solve that issue I am including two larger washers in the new kits that are for the center of the stack and actually are retained by the case rather than the retainer. They also hold the smaller washers in place because of the way they engage. This was rare but I want a solution that works for everyone in both the common and rare machining tolerances of the OBX LSD.

 

I updated the webpage a while back to describe this change (search for R200 in the page).

http://rbryant.freeshell.org/obx_washers.htm

 

For the time being I am also including enough washers so that if the retainer is able to surround the stack (which I don't think any of them are) you can use all small washers. If you use the larger two washers you will have some of the small ones left over. Hopefully that doesn't make things too confusing...

 

I think at the time TrumpetRhapsody got them I was using some thicker washers which worked ok but I think that even he said the stack was shorter than he would have liked.

 

Your washers are a little bit thinner than the previous ones but they are also chrome vandium which makes them even stronger.

 

I am just trying to improve things. The latest configuration has been tested by another R200 differential customer and I believe that you will find it to be superior.

 

-Rich

 

**IMPORTANT:** [This was the case with my OBX unit]

 

Just make sure that the large washers are not touching the edges of the retainers. The smaller washers need to be what is contacting the large ones. The retainers themselves should not touch the larger washers.

 

If your retainers are longer and touch the large washers then you can just use all small washers (that hasn't happened to anyone yet but I included extra small washers just in case).

 

Thanks and sorry for any confusion on this. Given that your roommate tried the other configuration I am interested in hearing his thoughts on which is better. Ironically I think it was actually one of his comments on a forum that prompted me to change what I provide.

 

-Rich

 

Thanks for all of the R&D and for offering these kits, Rich! It's very nice to get quick replies back to questions. The shipping was also very quick.

 

*Also:*

 

Be sure when swapping all the gears around that BOTH axle circlip grooves are toward the inside of the case. This will ensure both axles will clip in properly.

 

Remember to do this as well, if your gears came in the improper orientation, you will need to switch [and flip] the 'top' gear with the 'bottom' gear. The circlip grooves will be towards the inside of the case if you've done it properly.

Edited by flatblack280

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jc8587    0

Here are some photos of the 5MT with an OBX in it, but it doesnt show the orientation of the gears:

 

IMG_0119.jpg

 

IMG_0120.jpg

 

 

As you can see, the axle splines are on the diff itself, as the axles do not clip in, but are attached via compression pins.

 

Will I need to shim the diff, from side to side, axle to axle? Shimming the bearings I mean?

 

As you can see in the photo, the bearing looks to be pressed on all the way to the housing.

 

Will I need new bearing for the axle shafts?

 

New seals?

 

 

I also have the kit from RBryant. I hope that hardware works!

Edited by jc8587

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The Woj    27

Crap, so I just rebuilt the OBX and had the bearings rebuilt and bolted back together by a diff shop - but I checked the pic's of my teardown and the gears are in the wrong direction. How bad would it be to run with the gears turning the wrong way?

 

I actually tried to remove the carrier since the shop put it in, but could not get it out (I forgot to put the circlips in, but I managed to get them in from the sides).

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FlatBlack    17

Here are some photos of the 5MT with an OBX in it, but it doesnt show the orientation of the gears:

 

http://i19.photobucket.com/albums/b181/Crazykevwrx/IMG_0119.jpg

http://i19.photobucket.com/albums/b181/Crazykevwrx/IMG_0120.jpg

 

As you can see, the axle splines are on the diff itself, as the axles do not clip in, but are attached via compression pins.

 

Will I need to shim the diff, from side to side, axle to axle? Shimming the bearings I mean?

 

As you can see in the photo, the bearing looks to be pressed on all the way to the housing.

 

Will I need new bearing for the axle shafts?

 

New seals?

 

 

It would be best to replace the carrier bearings, I'm going to use my old ones though.

 

For non-Subaru people, the front of the transmission is in the right of the picture. The axles come off the tranny directly after the motor:

 

IMG_0108.jpg

 

Your carrier is setup like the R160/R200 if I'm thinking about this correctly. The ring gear is on the driver's side of the carrier, like the rear diff

 

103_1784.jpg

 

So, it *should* be the same, and the gears need to be in the same orientation.

 

How bad would it be to run with the gears turning the wrong way?

 

The gears will 'slam' into the retainer/washer stack on acceleration, which is most likely the reason people complain about unmodified OBX LSDs obliterating the stock washer stacks.

 

From KA-T.org [A forum for turbo 240SXs]:

 

I have been running an OBX diff for about 18 months or so. Initially it works pretty well but after 6 months it wore out and was basically an open diff. At the time I did not have the cash to upgrade, so I took it apart and found the spring washeres inside were all worn, craked, and half of them were in pieces. Not knowing were to find replacement beveled washers, I simply put regular flat washers inside. I added enough washers to make sure their was going to be enough resistance to lock up the diff. Immidiately the diff worked great again.

 

The RBryant washers are much stronger, but it's only extra insurance. It's much better when the washer stack only sees pressure on engine braking [Like the Quaife unit].

Edited by flatblack280

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jc8587    0

How the hell does this work? I mean, I'm sure your right, but think about the following scenario via MSPaint!

 

With both ring gears on drivers side, the rear moves opposite the front.:

LSD%20wrong.JPG

 

 

With rear diff ring gear on passenger side, they move the same way. (ALTHOUGH I AM ALMOST 100% POSITIVE THAT THE REAR DIFF HAS THE RING GEAR ON THE PASSENGER SIDE ALSO!!!):

LSD%20right.JPG

Edited by jc8587

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jc8587    0

 

The gears will 'slam' into the retainer/washer stack on acceleration, which is most likely the reason people complain about unmodified OBX LSDs obliterating the stock washer stacks.

 

 

 

Ok, under acceleration you want the diff to lock up, right? So you want the axle gears to be pulled into the diff and touch the washer stack right?

 

So the axle gears should be "slamming" into the retainer/washer stack, right?

 

OR, will the gears be pulled in regardless of the orientation?

 

The reason we want to run the gears as said is because the barrel gears will crash into each other on acceleration if we do not?

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