The OBX Helical Diff Thread!!! Installed in S14!!!

[240shorty]

Finally got my OBX differential a couple of days ago. It's been about a month and a half, thanks to the wonderful folks at UPS. What can brown do for you?? Answer: Lose my packages.

INSTALL: I took 36 pics and was thinking of doing a writeup, but a differential install is a differential install. They are pretty much all the same, so I'll just point out the relevant stuff.

First it was installed into an open differential. There was some question as to which type it would work for. It appears to be designed for the open. The shafts fit in where they should be, flush with the housing, and the depth appears correct also.

I installed the unit myself. I checked the backlash of both the oem unit and the OBX. The OEM @ 140K miles had backlash measurements of .0045, .0055, and .0070. The latter being slightly out of spec. It worked well.

I removed the bearings with a puller and reused them. I used the original ring gear as well. Everything lines up and is cake to install on the OBX. Ring gear applied with red loctite.

BACKLASH: This is important. I DO NOT recommend installing one of these without checking backlash. Some people do it with the s15 diffs, but that is an OEM Nissan part. I tried the OBX with stock shims and the result was ZERO backlash. Spec is .0039 to .0059. The gears interlocked completely with no play whatsoever. I had stock shims of roughly .083 and .103 inches. I thought of swapping sides of the shims, but they would have moved the diff housing the wrong way. I did not have a shim pack, so I cut my own shims. I don't recommend this, but it works. I cut a ~.063 shim from sheet and 6 .005 shims from aluminum cans. Hoffbauer lager, to be exact. I used these shims in combination to eventually get the backlash within spec. I took many measurements ranging from .0035 all the way up to .008. Again, that latter is slightly out of spec, but it is close enough for me, and pretty much the same as the OEM unit.



I checked the tooth pattern with prussian blue. It was pretty heel heavy, but I did not intend to adjust the pinion, so it will have to do. This cannot always be adjusted properly anyway, as it depends on the pinion bore to housing alignment.

I should also note regarding bearing preload: I did not have a spring gauge to test preload. The OBX with stock shims, fell into place pretty easily. It required more shims than stock to create some preload. I simply gauged the tension on the OEM diff and tried to duplicate it as nearly as possible. I ended up using all 6 pop can shims as well as the homemade sheet shim, plus the OEM .103 and spacer. I discarded the .083 from the non-toothed side of the diff. I probably ultimately added somewhere between .010 and .020 shims total.

OBX with bearings and ring gear:



Including removal and replacing the housing there are several hours of work involved to do the job right, depending of course on working conditions and tools. I did it over the course of a couple nights, off and on, while taking pics and making notes.



REVIEW:

This is a preliminary, first impression type of review. I'll update my impressions over the next couple of days and add any relevant information regarding its performance. And of course, if it breaks.

After the install I took it out for a 20 minute test drive. Normal driving operation is, well, normal. Everything looks good so far. So I took it onto a dirt road first. I stopped in a few different spots, leaving one tire on dry gravel/dirt and the other tire in the ice and hard packed snow. I gave it a little brake and a little gas and let the clutch out to spin the wheels in place. I did this for a couple of seconds at a time to verify that the wheel with the most traction was spinning. The results are as expected. Both tires spun, and the tire with the most traction (dirt) spun continuously. Note: This is hardly scientific, as the application of the brake gives torque to both wheels, really negating the effect that might be experienced without braking. But it does prove that the differential is functioning and transfering torque.

Here is a pic showing the marks left by the tires on dirt and snow:



Next I took it to a paved road and parked it once again, half on pavement, half off the road in a snow covered gravel field entrance. I repeated the same methods used on the dirt road and once again the tire on the pavement broke loose. I did this only briefly as my winter tires smoke like the dickens and they are almost new.

I also opened up the throttle a bit on snow covered gravel to compare its response with the open differential. Both wheels spin and the rear end steps out more dramatically and quickly than with the open diff (of course).

This is about the extent of the testing so far. I didn't want to flog the car so fresh off the swap, and I will post more when I do.

In summary. So far, so good. I will update as appropriate.

-Steve

[kabukie]

Finally some posts a review!

Keep us updated!

[SR240DET]

haha i started laughing everytime i read the word "shim'' it started to lose its meaning...

nice write up.. finally somebody did one....

[i8yourfwd]

FINALLY! I'll be keeping my eyes on this thread. let us know when you take it for some "spirited driving"

[EvilRB]

great thread man!!
Keep us updated!

[WILDACEX187]

so does the obx unit have a more aggressive torque split than a s15?

[240shorty]

^If you are asking me, I can't answer that. I've not experienced the s15 yet. There is zero documentation that came with the unit. It comes in a white box with a cheap graphic saying 'OBX L.S.D.' and it's just a chunk of metal in a plastic bag. I never even got a reply from them when I emailed about which type diff it fit, so I'm not sure how to find out either.

[krustindumm]

Just an FYI, it only cost me ~$150 to have a differential setup last time (carried in). $50 was for new shims. Worth it, IMO, to have a diff setup properly.

[OptionZero]

I'm not really sure how a comparison to an open diff will be of any use.

What you should compare it to is a Welded Diff and a VLSD, which are the alternatives at a similar price point.

The compare it to the S15 HLSD, because that (and a Quaife...) are the alternative for those wanting a torque biasing diff.

Just saying that this works better than an open diff doesn't accomplish much.

[BigVinnie]

^^^Well atleast it is a better alternative than an open diff. Sucks though because modifying for a LSD diff case might be a bit more difficult, which means any of us that use LSD already really can't source this as an affordable alternative, (without B.S modifying). Which I thought that this is what it was for us LSD guy's.
Thanks for the info Steve, I guess I will look for other types of Torsens or Helicals that would be a direct bolt in for my case............

[ryangreg]

^^No differential is a drop in affair. Many people choose to go that route, but many people are hacks. Backlash must be measured, and dye should be used to see how the ring and pinion mate. If measurements arent taken, your gonna have a diff that is way louder than it was intended to be.

[240shorty]

Yes, I agree, the open differential comparison is pretty much useless. I was just pointing out that the diff was obviously doing it's job. I only have had access to an open and a welded. The welded diff I really don't like. It might be alright for drifting or strip, but daily driven I don't find the sacrifices in drivability acceptable. For me, after driving the welded, it was either stay open or go hlsd or possibly 1.5 way. I don't consider vlsd to be a good performance differential.

I like the fact that the hlsd is not apparent until you need it. No sacrificing drivability. I was a little torn between going S15 hlsd though. To me it is actually more risky to buy a new OBX than a used OEM part. But most of those actually go for more than this one, so... I went ahead and got it.

krustindumm, I have no doubt a shop install is worth it, but I like to learn the stuff myself when it is feasible. I familiarized myself with the steps involved and have enough tools and intelligence to do a fairly competent install. Or maybe I'm just a cheap a$$?

I didn't get to drive it today. My intercooler and piping came, so I did a little cutting and welding. Hopefully tomorrow I can finish up and get a good drive in.

[slideways2004]

can't wait for more of a review.

[gearhead290]

Originally Posted by ryangreg

^^No differential is a drop in affair. Many people choose to go that route, but many people are hacks. Backlash must be measured, and dye should be used to see how the ring and pinion mate. If measurements arent taken, your gonna have a diff that is way louder than it was intended to be.

I checked backlash, the R&P pattern, and preload on both my ATS and my buddy's Kaaz...all three were right where they were supposed to be. Many shops don't even check the higher end differentials, just drop them in and go.

[krustindumm]

Originally Posted by 240shorty

kristendumm, I have no doubt a shop install is worth it, but I like to learn the stuff myself when it is feasible. I familiarized myself with the steps involved and have enough tools and intelligence to do a fairly competent install. Or maybe I'm just a cheap a$$?

I was just making the post so other people would know that a shop install is a cheap option. Setting up a diff is VERY easy, if you have the right tools and shims on hand. I'm actually a Nissan Technician, but I took mine to a specialty shop because we don't stock shims, and I wanted it done right away. My car is my daily driver, so I can't have 2 days downtime while we order new shims.

[240shorty]

Alright, I was gonna update yesterday, but I kept having problems with my intercooler piping poppin' off. I did manage a couple of short runs, mostly N/A. I did a couple of burnouts/hole shots and the thing held up, but that is no feat for <150 horsepower (restricted intake). I can't comment much on traction though. Wet roads plus winter tires doesn't make for good traction.

I did notice one small thing that I don't particularly like, but I presume it to be normal. When initially releasing the clutch and starting off and on subsequent shifts it is possible to hear or feel a slight delay in the power application. It is very subtle, but I don't recall noticing it on the open. I have my interior out for now, so it is pretty easy to hear and feel everything in the car. I suspect it is the nature of the helical diff, when it's worm gears press outward and direct power to the wheels. I figure it is the mechanical action of the differential causing a momentary delay in power delivery. Perhaps someone with an S15 or Quaife could confirm whether or not this is the case.

Anyway, I did some more work today and welded a couple lips on the trouble areas of the intercooler piping. This time they held up and I got to take a few full throttle runs in it. This is the first time I've gotten to run for a signigicant time with sustained boost. Boost pressure runs between 8 and 10 psi and my timing is retarded to 15* and conservative AFR's around 10.5 to 11. I estimate it is producing somewhere in the ballpark of stock SR power, give or take. I'm still a little hesitant to go full throttle right off the line, I want to make sure everything is kosher and build a bit of confidence in it. But traction is alright and the diff has held up so far.

What I really need is some road coarse type testing or at least some tight cornering. This is of course, why you'd buy an hlsd in the first place. It's still winter here unfortunately, so no tracks will be open for awhile. I will do what I can on the public roads when we get some dry pavement.

Summary, I haven't broke it yet, but give me time. :')

[beavis360]

any update on this?

[tchenku]

i'm trying to keep updated, also. nothing as of yet. nothing on nico, either. either 240shorty is snowed in up where he lives or he's out having the time of his life with the obx lsd and has forgotten to keep us up to date.

[240shorty]

Originally Posted by tchenku

i'm trying to keep updated, also. nothing as of yet. nothing on nico, either. either 240shorty is snowed in up where he lives or he's out having the time of his life with the obx lsd and has forgotten to keep us up to date.

Well, they say no news is good news right? The differential is still doing fine.

I've been installing the new clutch over the past few days. I had a throwout bearing/fork issue the first time around, so I pulled it back down and fixed it. It's all good, now, but I'm still in the break in period so I've been taking it easy on the clutch.

I have not had much chance to flog the differential, but it is holding up well so far to my mildly boosted engine and some spirited driving. I just hadn't updated because I don't have any real relevant info to report on. I would like to get some launch times and hard cornering in, but that is still nearly a month off up here. Weather sucks.

Hope this will suffice for now. If not, well... tough luck.

Hasn't ANYONE else tried this diff yet?? I'd like to see someone elses thoughts on it. Specifically someone who has driven with an S15, Quaife, or clutch diff in a 240. I have yet to drive any of them. Only open, welded, and OBX. So in my very limited experience, OBX is EASILY the most superior. I'd like to know myself how it compares directly to the 'heavy hitters'.

-Steve

[infinitexsound]

im procrastinating on trying it out seriously, my viscous is goin out...and i would either replace it with a 2way clutch type pref.. a nismo one.. or that obx one to see how well it holds up...

[Skyline0586]

i laughed when i saw OBX..

[AzNCmB]

for the price, i would like to try it because i think my vlsd is going out to0

but....i will do more research on diff installs just to be sure if i can attempt this myself...

please keep us updated..thanks

[nrg]

isn't this just a HLSD? There are tons of reviews on these obx lsd on honda-tech.com
I think there's a 450whp drag car using one.

best way to test this diff is to drift or road race on it.

[KA24DESOneThree]

Do you read AT ALL?

1. It says helical in the thread title.

2. He lives in Michigan. Track time in March in Michigan is hard to come by.

[timtiminy]

okay well i am interested in this soley for grip driving because of the torsen diff is more adequate for handling than drifing. I am looking for some info from 240shorty about the way this thing handles, i am sure its a huge improvement over an open diff. So its spring now...is there still snow or can you go on an dry road and tell me how this thing performs??

[240shorty]

Well, the weather IS better here now and I have been doing some driving. Only on the street though. I like the way it launches; I like the way it feels in corners; I like the fact that it hasn't broken.

I have very limited experience with 240 diffs, but off the line the difference in traction is noticable. I was doing some launching the other day on the street and was fairly impressed with traction out of the hole. Keep in mind I've been driving on 7.5" wide wheels with crap Korean rubber. Any attempt at a hard start with the open diff resulted in a spectacular one tire fire. Even with the crap tires and the helical, I have found it hard to break traction without trying to do so. Raising the revs to around 3k and nearly dropping the clutch did result in some squeeling, but not a full on burnout. The tires did chirp repeatedly, but they got plenty of traction to propel the car forward. I am not skilled in the art of drag launches, but feel that with practice one could do very well with this diff.

In corners, once the car loses traction, it feels very similar to any locking differential. The ass end slides out easily as both tires spin. The big difference though, is that up until you cross that threshold, traction is solid and handling is smooth. I want to make clear this difference. Driving a helical through corners is smooth and well planted, though much will still depend on your tires. Driving my brother's welded through corners is a jerky, un-inspiring proposition. In fairness, a welded is better for drifting (which I don't do) and attracting law enforcement officers (which I don't like to do) and 16 year old rice loving boys (which I hope to hell I don't do).

I have not intentionally neglected this thread, but having not taken this thing to the limit, I cannot give a true and full review of it. It's still 'so far, so good', and time will tell.

The true test will be in a few weeks. My Holset arrives Thursday and my tax refund will be funding my new wheels and tires within ~3 weeks. I also went back to work today finally. So in under a month, barring an act of God, I should be sporting 300+ hp, 10.5 inch wide tires and hopefully a little suspension too. Then I will know without a doubt if the OBX Helical LSD is up to the task.

And I know I'm not the only one who's bought one of these, so where are the rest of the reviews???

To those who are hesitant: It is not that much money to have the diff installed by a shop (from what I've heard). You can get a cheap, but adequate digital dial indicator and base from Harbor Freight. You can pick up Prussian Blue from Car Quest. And you can get free install instructions from F.S. Manual and your good friend Mr. Google.

In the interest of being completely candid and offering full disclosure: I alluded to something I noticed in the drivetrain previously. I will try to describe it more clearly. When the drivetrain goes from an 'unloaded' to a 'loaded' state, there is what I'd describe as a small 'shock loading' that occurs. This is noticable in certain situations and is affected by the type of driving and especially the clutch release. I am not 100% certain of the origin, but I have attributed it to the diff as I noticed it shortly after the install. There is a possibility that it is tranny related or possibly compounded by my VERY tired engine mounts. I also have a 6 puck clutch which no doubt makes it more noticable. Bottom line: It might not be noticable with a street disk and it is possibly not even diff related (though I believe it is).

I tell you this so those who may be looking at this diff can make an informed decision. I do consider it a 'minor' annoyance and would still take this diff over any other option, with the possible exception of an S15 or Quaife HLSD. Those IMO are the two relevant comparisons here. The Quaife is not comparable in price, but the S15 is fairly close. It is a question of new OBX vs. used OEM.

OBX pwns Open, period. My personal prejudice towards viscous coupling dictates that OBX > VLSD. For my usage, OBX > welded or any clutch diff. I would guess, but cannot say that Quaife > OBX. They may perform comparably. I am not qualified to make this comparison.

For anyone considering swapping to a VLSD, who isn't into drifting, I'd say you are doing yourself a big disservice if you don't consider this diff. You are going to spend enough time and money for that swap, and subsequently enough time wondering when your viscous is going to turn into an open, that you'd be better of going with this diff.

Whatever. I'm not a salesman or an OBX fanboy so... [/commercial]

Your car. You decide.

[i8yourfwd]

Yay finally an update! thanks for not forgetting about us taht want to hear about it :]

Describe the "shock loading"?

[mikesim]

since i've never looked inside my VLSD, can this OBX install into it without modification? or is it only meant for open diffs?

[240shorty]

See, now that phrase sounds bad. I don't know if it is a good choice. All I am trying to say is that there is a small ammount of 'slop' in my drivetrain somewhere. Let's say I'm cruising around town gently shifting through the gears. When I let of the gas to upshift there is no load on the drivetrain. I upshift and release the clutch. Upon release, there is load put back on the drivetrain. Somewhere in the drivetrain it feels like there is a certain ammount of give between mechanical components. So it will give a little 'clunk' as (or slightly after) the clutch engages the flywheel. It comes after the clutch release, with a momentary delay.

It is not the clutch that makes the 'clunk'. This much I can tell. You can also eliminate it by consciously releasing the clutch more gently. For this reason, I suggest it might be un-noticable with a normal street disk. The source of the give in the drivetrain could very well be my tranny, the rear, or maybe a faulty joint in the rear axles. I cannot say for certain. It could even be bushing related.

I could not give a complete review without including it though, as it may very well come from the rear. That is when I noticed it, so that's where I'd tend to attribute it.

I've gotta get to work, but hopefully this explanation helps to describe it better.

-Steve

[240shorty]

Originally Posted by mikesim

since i've never looked inside my VLSD, can this OBX install into it without modification? or is it only meant for open diffs?

I believe the open and viscous use different lengths of output shafts/flanges. The one side would probably stick out too far and the other may not engage properly. I believe you'd need the open outputs.

I never got an answer from OBX on which it was supposed to fit, but the flanges line up flush with my housing on both sides.