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Thread: Did OBX mess up my LSD?? (long post)

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    Supporting Member Turbo Mopar Contributor jonnymopar's Avatar
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    Did OBX mess up my LSD?? (long post)

    So here I am, over-thinking things as usual. Please someone chime in and either tell me if I'm right or if I'm an idiot. I took my OBX apart and I'm a bit confused as to what I'm looking at here. I confirmed that when the diff is in use, the two large side gears are supposed to be forced outward, away from the belleville washers.

    Here's a view of the guts in my OBX, basically as viewed from the driver's seat with the transmission installed:



    Looking at the gears and the way the helix is cut on each of them, applying rotation to the case and resistance to the large gear visible in the picture would result in that gear being drawn inward, not outward as it's supposed to be. Ok, so I'll switch the gears left to right and that should solve the problem. I found out quickly that it's impossible to do. Below are the two large side gears that the axles engage with. Passenger side gear is on the left. Driver side gear is on the right.



    Ok, they're two different sizes. If I put the small gear on the passenger side...



    ...followed by the piece where the thrust washers drop into...



    ...followed by the larger of the two gears...



    ...the larger gear interferes with the small helical gears:



    So the only way that the gears can go in is like this (again, as viewed from the driver's seat with the transmission installed). This results in the gears being drawn inward under torque:



    Now to test your eyes. Take a look at this picture (this picture belongs to Rich Bryant and is on his OBX rebuild page):



    It may be hard to see, but compare the above picture to the first picture in this post. The gears are cut in opposite directions! Am I doomed here? Do I just have to deal with it? I can't flip my gears so they face the way they do in the above picture.

    My differential is modified, but only the holes where the ring gear bolts to. I don't know if that's enough to void my warranty. If you've made it this far through this post, I sincerely thank you for your time.

    Any ideas?
    Last edited by jonnymopar; 05-08-2014 at 01:08 PM.
    Jon J.

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    Re: Did OBX mess up my LSD?? (long post)

    Your over thinking it. Ok, I said that now here is the point to understand. This is not a POSI unit or any other diff that delivers power to both tires at the same time as we have come to understand such things like the RWD cars of old. They used clutches, springs, blocks and such to apply force to either the side spider gears or clutches or cones depending on the unit.

    The OBX, like it's parent, the Quaife are a Torque biasing differential and apply power the the wheels with LESS traction, not both at the same time. If you dump the clutch at 6K RPM (a really dumb idea on a FWD trans, I'm just saying) and the LF tire hooks and the right starts to spin, the power is directed to the spinning wheel. This can switch back and forth during the "loss of traction process"

    At no time will you have a nice two wheel tire fire going, just an application of power to the tire with less traction.

    SOOOOOOO, with that being said, I hope you remember how it came apart, put it back together, apply some loctite to the bolts, torque them to about 150" lbs, install the ring gear and get it in the transmission. Don't forget to set the differential bearing preload, don't want to trash a new set of diff bearings and other parts.

    Cliff Ramsdell
    The "Retired" Transmission King
    But I still know a few things.

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    Supporting Member Turbo Mopar Contributor rx2mazda's Avatar
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    Re: Did OBX mess up my LSD?? (long post)

    Quote Originally Posted by Cliff Ramsdell View Post
    Your over thinking it. Ok, I said that now here is the point to understand. This is not a POSI unit or any other diff that delivers power to both tires at the same time as we have come to understand such things like the RWD cars of old. They used clutches, springs, blocks and such to apply force to either the side spider gears or clutches or cones depending on the unit.

    The OBX, like it's parent, the Quaife are a Torque biasing differential and apply power the the wheels with LESS traction, not both at the same time. If you dump the clutch at 6K RPM (a really dumb idea on a FWD trans, I'm just saying) and the LF tire hooks and the right starts to spin, the power is directed to the spinning wheel. This can switch back and forth during the "loss of traction process"

    At no time will you have a nice two wheel tire fire going, just an application of power to the tire with less traction.

    SOOOOOOO, with that being said, I hope you remember how it came apart, put it back together, apply some loctite to the bolts, torque them to about 150" lbs, install the ring gear and get it in the transmission. Don't forget to set the differential bearing preload, don't want to trash a new set of diff bearings and other parts.

    Cliff Ramsdell
    The "Retired" Transmission King
    But I still know a few things.
    Don't you mean it applies power to the wheel with more traction and away from the spinning wheel? This back and forth action is what makes it a LSD. If it directed all the power to the wheel with LESS traction(like a non LSD diff) then it would only spin one tire.

    EDIT: From Quaifes website.......".... because unlike a conventional plate-style LSD, it never locks harshly with a set pre-load of wheel slip across the driven axle. Rather, it automatically biases the torque away from the spinning wheel across the axle, to a constantly varying degree and never locks."

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    Supporting Member Turbo Mopar Contributor jonnymopar's Avatar
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    Re: Did OBX mess up my LSD?? (long post)

    Thanks for the input guys. I know what the differential does and why it's different than a locker or a clutch style LSD. That's not what I'm concerned about here. I'm concerned about a technical aspect inside the unit. I finally found a thread that explains exactly what I'm highlighting above:

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

    Read post 5. This is what I'm talking about here. It's not that I don't know how the differential works. It's not that I don't know how it goes together. I'm focusing on what I believe to be a fundamental flaw in the operation of the unit, at least with the unit I have. With some of the quality nightmares that I've read about with OBX products, I wouldn't be surprised in the least if only some of them out there were wrong. If the two sun gears weren't different sizes, I would have never posted this. I would have flipped everything around and been on my way, confident that the helical teeth were correctly oriented.

    The belleville washers are preloading the gears outward. With the way the teeth are cut on mine, every time you launch the car, those gears are getting violently shoved toward eachother, instead of being pressed against the case (which is a larger bearing surface to support the side of the gears). If the gears were meant to go inward, the gears would have been preloaded from the outside.

    I dunno.
    Jon J.

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    Re: Did OBX mess up my LSD?? (long post)

    Jon

    I see what you mean, and to add insult to injury look at post #23 in this thread. It clearly shows the helical gears in Turboshad's OBX cut in the same direction as Rich's. (which is opposite to yours) Basically what your saying is the OBX appears to be built for a transmission in which the OBX would rotate in the opposite direction to work correctly (so it would work well in reverse in ours transmissions) nice.
    http://www.turbo-mopar.com/forums/sh...ight=turboshad

    I'm just at work, but I've got an OBX apart on the bench at home that I bought from TU about 2 years ago. Im curious how my gears are cut. Ill let you know. And also I need to clear the cobwebs out of my head since I'm working nightshift and get this whole thing straight in my mind.

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    Supporting Member Turbo Mopar Contributor jonnymopar's Avatar
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    Re: Did OBX mess up my LSD?? (long post)

    Thank you for the link to that thread! I had searched the death out of this forum and the pictures that I was really looking for were right in front of me!

    Ok, for the money shot:

    DJ's passenger-side gear:



    My passenger-side gear:



    This is what I'd like to get fixed. Because all 10 of the outer helical gears are the same length and diameter (just 5 in one direction and 5 in the other), I'm pretty confident that I could get away with simply replacing the two side gears and call it a day. From what I've seen, the Neon OBX seems to be on backorder from the factory, but only shortly. We'll see how this goes.
    Jon J.

    1989 Daytona ES 2.4L DOHC
    2003 Neon SXT - gone but never forgotten

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    Re: Did OBX mess up my LSD?? (long post)

    Somebody put the part in backwards during machining if those pictures are what you say they are.
    Brent GREAT DEPRESSION RACING 1992 Duster 3.0T The Junkyard - MS II, OEM 10:1 -[I] Old - 11.5@125 22psi $90 [U]Stock[/U] 3.0 Junk Motor - 1 bar MAP [/I] 1994 Spirit 3.0T - 11.5@120 20 psi - Daily :eyebrows: Holset He351 -FT600 - 393whp 457ft/lb @18psi 1994 Spirit 3.0T a670 - He341, stock fuel, BEGI. Wife's into kid's project. 1990 Lebaron Coupe 2.2 TI/II non IC, a413 1990 Spirit 3.0 E.S. 41TE -- 1993 Spirit 3.0 E.S. 41TE -- 1994 Duster 3.0 A543 1981 Starlet KP61 Potential driver -- 1981 Starlet KP61 Parts -- 1983 Starlet KP61 Drag 2005 Durango Hemi Limited -- 1998 Dodge 12v 47re. AFC mods, No plate, Mack plug, Boost elbow -- 2011 Dodge 6.7 G56

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    Re: Did OBX mess up my LSD?? (long post)

    So I checked my OBX and my gears are machined backwards as well (same as yours Jon). I bet the whole production run was machined wrong. I recall someone posting a question a while ago about thinking thier OBX was assembled backwards also, so I bet there are more out thier on this board with this problem since this particulat OBX cant be assembled backwards.


    I guess we'll have to contact OBX to see if they will buck up and give us internals that are machined properly. But I know what they'll say.

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    Re: Did OBX mess up my LSD?? (long post)

    Which production run did you guys buy..... I had the first lot that T.U. was selling.
    Brent GREAT DEPRESSION RACING 1992 Duster 3.0T The Junkyard - MS II, OEM 10:1 -[I] Old - 11.5@125 22psi $90 [U]Stock[/U] 3.0 Junk Motor - 1 bar MAP [/I] 1994 Spirit 3.0T - 11.5@120 20 psi - Daily :eyebrows: Holset He351 -FT600 - 393whp 457ft/lb @18psi 1994 Spirit 3.0T a670 - He341, stock fuel, BEGI. Wife's into kid's project. 1990 Lebaron Coupe 2.2 TI/II non IC, a413 1990 Spirit 3.0 E.S. 41TE -- 1993 Spirit 3.0 E.S. 41TE -- 1994 Duster 3.0 A543 1981 Starlet KP61 Potential driver -- 1981 Starlet KP61 Parts -- 1983 Starlet KP61 Drag 2005 Durango Hemi Limited -- 1998 Dodge 12v 47re. AFC mods, No plate, Mack plug, Boost elbow -- 2011 Dodge 6.7 G56

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    Re: Did OBX mess up my LSD?? (long post)

    I just checked my TU account and it was shipped June 2012.

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    Supporting Member Turbo Mopar Contributor jonnymopar's Avatar
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    Re: Did OBX mess up my LSD?? (long post)

    Mine shipped 5/10/13. I wonder how many units are in a lot.
    Jon J.

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    Re: Did OBX mess up my LSD?? (long post)

    btw, are you wondering anymore why they might be on backorder? :P
    Brent GREAT DEPRESSION RACING 1992 Duster 3.0T The Junkyard - MS II, OEM 10:1 -[I] Old - 11.5@125 22psi $90 [U]Stock[/U] 3.0 Junk Motor - 1 bar MAP [/I] 1994 Spirit 3.0T - 11.5@120 20 psi - Daily :eyebrows: Holset He351 -FT600 - 393whp 457ft/lb @18psi 1994 Spirit 3.0T a670 - He341, stock fuel, BEGI. Wife's into kid's project. 1990 Lebaron Coupe 2.2 TI/II non IC, a413 1990 Spirit 3.0 E.S. 41TE -- 1993 Spirit 3.0 E.S. 41TE -- 1994 Duster 3.0 A543 1981 Starlet KP61 Potential driver -- 1981 Starlet KP61 Parts -- 1983 Starlet KP61 Drag 2005 Durango Hemi Limited -- 1998 Dodge 12v 47re. AFC mods, No plate, Mack plug, Boost elbow -- 2011 Dodge 6.7 G56

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    Supporting Member Turbo Mopar Contributor jonnymopar's Avatar
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    Re: Did OBX mess up my LSD?? (long post)

    Quote Originally Posted by Ondonti View Post
    btw, are you wondering anymore why they might be on backorder? :P
    I spoke with Chris at Turbos Unleashed about this issue tonight and he brought up that point, which I though was pretty interesting. I'm really hoping that's why they were on backorder. At least that means that the new units will be right (and there's hope that I might be able to get good parts for mine). Chris was even nice enough to offer to open up a Quaife in stock to see which direction the gears should face.

    I bet there's a halfway-decent demand for this part, considering it fits 520/555/523/568/T350 and whatever gets bolted to a 420A in the Eclipse/Avenger.
    Jon J.

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    Re: Did OBX mess up my LSD?? (long post)

    I doubt backorder is to fix this issue, mainly from lack of demand compared to other cars that sell more parts. And "backorder" length has been pushed off several times now. I was told mid-April in March, and 45-90 days at end of April. No update as of last time I asked, and I'm trying to get 8-10 more. Our cars are old news and not that many people buy diffs. Even if 20 sell a year, that's not that many. OBX doesn't care, it's why I gotta take apart every one I get, cut the splines down for axle clip (Neons), press bearing on and make sure axle still fits after bore is squeezed down a bit, and gotta take die grinder to brand new $15 speedo sensor gear to make it even snap on. Just checked 2 sets I had in the shop. RH gears from old school (7+ years old, seeing how we pressed the axle out of it when I was still in tech school 6 years ago). LH gears from batch shipped last March from OBX (the ones Modern had as well), of which I had received and sold 8. For what it's worth, everybody that I've sold a new one too has said they work great.

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    Re: Did OBX mess up my LSD?? (long post)

    Not sure I follow what Dogg is saying completely So even machined backwards they still work as an LSD? BTW I have 3 cars with OBX LSD's, 2 were definitely built before 2010-2011 so those are safe. But that last one

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    Re: Did OBX mess up my LSD?? (long post)

    There are quaife pictures on here somewhere. I think Reeves posted them.
    Last edited by 83rampage; 05-14-2014 at 02:17 AM.

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    Re: Did OBX mess up my LSD?? (long post)

    Here is a quaife posted by Reeves. It clearly shows the OBX gears are backwards.

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    Re: Did OBX mess up my LSD?? (long post)

    From what I've been told, yes they still work great. And I've been thinking about it. Under no circumstances will both side gears be pushed together OR apart. When your diff is spinning and both wheels are spinning the same speeds, none of the gears inside it are rotating with respect to the housing, same as an open differential. The load is transfered from the ring gear, to the case, to the sets of helical gears, and through the side gears out both axles.

    Now if the right wheel starts to spin, and the left wheel slows down (wet pavement on right side), the right gear will start to spin FORWARD while the left gear spins BACKWARDS with respect to the housing. With old style gears, it'll push both side gears to the left inside the case (right one will push in, left one will push out). New style gears, they'll go the other way. How much do they actually move? I'll have to assemble a diff with no washers and put a dial indicator on them. Either way, it will compress the washers as the gear being pushed out will hit the case and can't move. So regardless of which way the gears move (and not much at all), you still end up with a set of meshed helical cut gears that are all rotating at different speeds.

    This is from the website for Truetrac differentials, which are same theory from pics:

    "The Truetrac uses the separation action of helical gears, caused by differential speed, to control whichever wheel starts to rotate faster. As the gears are loaded, the separation presses the end of the gears into hardened steel pockets thus braking the faster wheel. This mechanism acts in the same way as a standard differential gear train until wheel speed differences are greater than normal, i.e through the sudden wheel acceleration caused by loss of traction. Steering and general vehicle function is unaffected by this gear system"

    So regardless of which way they are cut, the whole system will move one way or the other, and force the worm gears against the pockets in the diff and slow down the faster wheel, and apply power to the slower wheel.

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    Supporting Member Turbo Mopar Contributor jonnymopar's Avatar
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    Re: Did OBX mess up my LSD?? (long post)

    Even though I’ve never had a car with any type of LSD before this, I will say that this LSD with the backwards gears is better than open diff! Whether it’s working properly or not, it is working at least to some degree. Even if the gears are getting forced against the “star” looking piece that houses all the thrust washers, they’re still getting forced against something. Obviously there’s not nearly as much of a bearing surface there as there is against the outside of the case.

    Chip, when it comes to FWD Chrysler transmissions, I hold you in very high regard, especially with your contributions to the Neon community with your extensive knowledge of the T350. But I respectfully disagree with the statement that under no circumstances will both gears move in or out simultaneously. When you launch hard (which I would make a guess is when ANY differential sees the most stress on all of its internals, regardless of its design), those sun gears are absolutely moving opposite of each other. You are correct in saying that none of the gears are moving relative to each other inside when both wheels are moving at the same speed, but that doesn’t mean there isn’t tremendous force against them. When there’s force between two meshed helical-cut gears, there’s going to be side force in one direction or the other simply due to the way the teeth are cut.If the teeth were straight-cut, you wouldn’t have that, but this whole design wouldn’t work too well. Even with a little bit of wheelspin on launch, those gears are spending most of their time with side forces exerted in opposite directions. Inside the OBX you have that’s several years old, those gears will move out during that hard launch. Awesome. With the newer ones like mine, they get shoved in.

    I’ll throw this out there too: when I took my differential apart this time, the case didn’t seem to spring apart as much as it did when I first took it apart last year to machine the ring gear holes. I don’t have any new Belleville washers to compare mine to, but they do not seem to have as much spring to them as they did new. I don’t know whether that’s due to the hammering action of having the gears cut backwards, or if it’s simply inherent to having them compressed.
    Jon J.

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    Re: Did OBX mess up my LSD?? (long post)

    It's Cliff

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