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OBX vs Quaife (with pixors)

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I think you are good with the quaiffe. It's just us penny pinchers that need to be concerned about the OBX units. I began taking my OBX apart tonight for a washer change and inspection. Structurally and quality-wise, it seems quite good. The metals used seem very hard. I will check the stubs if I get time. I was told by another member that uses the OBX, that the 280Z and 280ZX inner stubs fit fine. I will double confirm when I can.

 

Pics on the way

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OK I played around with the OBX on the floor of my house (too cold in the garage).

 

This is how it works.

The large side gears are splined correctly for the 280Z 280ZX inner axle stubs. When forward torque is applied to the ring gear, the left and right side gears are PULLED into eachother, towards the center of the diff. This is due to the spiral (angle) cuts in the gears. Sandwiched between them is the star shaped "clutch" that is filled with spring washers. The spring washers are compressed by the two colliding side gears as the side gears bite onto the central "star" shaped "clutch". On neutral input torque, the spring washers push the side gears back outwards, away from the central "star-clutch" and into the inner walls of the gear case. In reverse torque on the ring gear (engine braking) the side gears are forced outwards into the inner walls of the gear case.

 

There is also friction created from all the thrusting around of the thinner spiral gears as they press into their pockets and their ends drive into the case walls under pressure.

 

(point to note: the groove inside the side gears for the axle retainer ring is made extra wide to allow the side gears some side to side action without pulling on the axles)

 

BOTH decel and accel will produce some level of LSD action.

 

THE SPRING WASHERS:

They are merely there to keep the outer gears from slopping around during transistions from accel to decel. If the stack is too short, you get slop and the gears rattle. If the stack is too long, you get some preload when you screw the case together and the diff will never act like a FULLY OPEN diff. The spring preload forces the side gears outwards to press against the inner case walls.

 

NOTE:

If the outermost spring washers are installed (xxxx) the end of the stub axles CAN rub into them. I reccommend installing the outermost washers like this )xxxx(

 

I chose to assemble with one-washer-thickness of preload. Using the McMaster washers I did this:

 

))()()((

 

This makes the diff slightly preloaded with hopes of keeping the slop to a minimum when getting on and off the throttle.

 

 

R200 280Z Axle Stubs:

462569159_3VPWS-XL.jpg

 

462569330_XkC9P-XL.jpg

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I never actually paid any attention to how these diff work until I saw the last pics in your post. seems simple enough. makes it easy to see how the planetary gears move power from one side to the other.

 

so are you replacing the cap-screw bolts with 12.9 grade?

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These are the screws that came in my unit. :wink:

 

462493439_nsyAE-L.jpg

 

 

I don't have a Quaife to study, but from all the cutaway's I see, the OBX and the Quaife work oppositely. The OBX forces the side gears toward eachother under acceleration and the Quaife forces the side gears apart during acceleration. This might have gotten them around any patents that might be involved.

 

If my assumptions are correct, and I very well could be wrong, then OBX should have put the bellville springs outside of the side gears, forcing them inwards to take up slack. This design reversal could explain the abuse imposed upon the OBX washers and the slack felt in some peoples driveline when going from accel to decel.

 

NOTE THE OPPOSITE ANGLE OF THE SIDE GEAR TEETH:

OBX

462493812_DaVQP-S.jpg

 

Quaife

F23.jpg

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I don't have a Quaife to study, but from all the cutaway's I see, the OBX and the Quaife work oppositely. The OBX forces the side gears toward eachother under acceleration and the Quaife forces the side gears apart during acceleration. This might have gotten them around any patents that might be involved.

I'm having a hard time with this, and I'll tell you why. Dana's helical LSD the True-trac comes in a "front" and "rear" version for the Dana 30 (front might be for a Jeep front diff, rear might be for a Volvo sedan). The difference is that the gears are flipped around, and that's the only difference. In fact, I've flipped them for a customer who needed one right away when I sold diff parts. The lockup on the diff should come from the side gears and helical gears driving into the ends of the case and also from the teeth of the helicals wearing on the case too. I had a .pdf that had breakaway pictures and showed torque vectors and all sorts of cool stuff, but I no longer have it and can't find it online. I think Drax240z posted one for the torsen LSD as well.

 

I did quote part of both .pdfs in this thread: http://forums.hybridz.org/showthread.php?t=93879

 

Here are a couple of excerpts:

 

The Truetrac can transfer up to 3.5 times more torque to the high traction wheel. This torque transfer ratio (called the bias ratio) is accomplished by using helical side gears and pinions. The bias ratio is the result of the pressure exerted by the side gears and pinions against the surface of the differential case. In certain applications, this normal gear engagement may produce temporary driver feedback.

 

The characteristic of torque bias is achieved in a very simple way. It is well known that frictional forces are determined by the product of the coefficient of friction of a given surface and the normal force applied to that surface. Frictional torque, of course, is merely the application of that normal force at an effective frictional radius. All of the forces which are active within the differential are derivable from the torque which is being conveyed by the differential and the friction coefficients of surfaces within the differential. Therefore, all of the frictional forces which are generated within the differential, and all of the resulting resistant torques which oppose the transfer of torque between drive axles, are proportional to the torque being conveyed by the differential. Since the maximum difference in torque between drive axles which can be supported by friction is proportional to the combined torque of the drive axles, the maximum bias ratio remains constant with respect to changes in the combined drive axle torques.

 

In addition to providing a geared interconnection between drive axles which permits the usual opposite relative rotation between the drive axles, the gearing also distributes forces which may be generated to resist differentiation over a large number of different surfaces within the differential. The surfaces over which the Invex gearing distributes forces are designed with different coefficients of friction and the Invex gearing is designed to distribute different loads between the surfaces. Collectively, the surfaces and the gearing are designed to distribute wear evenly over the surfaces and to control the overall amount of friction within the differential needed to achieve a desired bias ratio.

 

This section of the paper provides a mathematical representation of the basic frictional relationships within a Torsen differential which are responsible for achieving the bias characteristic between drive axles. The mathematical representation assumes that the direction of torque transfer through the differential is from a vehicle's engine to the drive axles. Figure 4 may be again referred to for identifying differential components mentioned in this section. However, specific forces and torques which are mentioned in this section are illustrated in Figure 5 in association with a schematic depiction of key differential components.

 

Engine torque applied to the ring gear (Trg) is substantially equal in magnitude to the sum of reaction torques which are developed at each drive axle (T1, T2). The engine torque is transferred to the drive axles through

(a) the differential housing which supports the ring gear and (B) the Invex gearing which is carried within the housing and interconnects the drive axles for equal but opposite directions of relative rotation with respect to the housing.

 

Thus, in addition to transferring torque from the differential housing to the drive axles, the Invex gearing also provides a rotational interconnection between drive axles which may be understood to function as a gear train for transferring torque between drive axles. Gear trains, of course, develop various reactions at gear meshes and mounting surfaces which generate friction opposing rotation of the train in proportion to the torque being carried by the train. Since all of the engine torque which is transferred to the drive axles is carried by the Invex gearing, reaction torque which opposes rotation of the Invex gearing is proportional to the engine torque which is transferred to the drive wheels. Thus, the transfer of torque between drive axles is also resisted in proportion to the transfer of torque between the engine and drive axles.

 

This feature enables the Torsen differential to support a torque imbalance between drive axles which contributes to the total amount of torque which can he transferred from the engine to the drive axles when the amount of torque which can be supported in one of the drive axles is limited by available traction. The major frictional interfaces which are responsible for supporting a torque difference between drive axles are listed below along with parenthetically enclosed symbols representing the coefficients of friction of the respective interfaces.

 

Side gear to element gear Invex gear meshes (µ1,)

Element gear faces to differential housing (µ2)

Side gear face to side gear face (µ3)

Side gear face to differential housing (µ4)

Typically, the largest reaction forces within the differential are side gear thrust forces (Fa1 , Fa2)

resulting from normal tooth loads (F1 , F2) acting at the side gear to element gear Invex tooth

meshes. The reaction forces are related to the normal tooth loads according to the following

equation:

 

Fa1 , Fa2 = (F1 , F2) x Cos ø x Cos ß

 

where 'ø' is the tooth normal pressure angle and 'ß' is the side gear helix angle.

 

These reaction forces are opposed by the respective frictional interfaces associated with the end

faces of the side gears and result in the generation frictional torques (Tf3 , Tf4) which oppose side gear rotation. These frictional torques are related to the reaction forces according to the following equation:

 

Tf3 , Tf4 = (Fa1 , Fa2) x (R3 , R4) x (µ3 , µ4)

 

 

where 'R3' and 'R4' are the effective friction radii at the respective side gear interfaces.

 

Frictional torques (Tf5 , Tf6) are developed at the respective interfaces between the element gears and differential housing. These frictional torques are also developed as a result of reaction forces at the side gear to element gear meshes, but the reaction forces being considered here are those which are directed along the respective axes of the element gears. These reaction forces (Fb1 , Fb2) are related to the normal tooth loads according to the following equation:

 

Fb1 , Fb2 = (F1 , F2) x Cos ø x Cos ß

 

The above-mentioned frictional torques (Tf5 , Tf6) are related to the reaction forces (Fb1 , Fb2)

according to the following equation:

 

Tf5 , Tf6 = (Fb1 , Fb2) x (R5 , R6) x (µ5 , µ6)

 

where 'R5' and 'R6' are the effective friction radii at the respective element gear to housing interfaces.

 

In addition to the frictional torques developed at the Invex gearing mounting surfaces, sliding contact between the side gears and element gears at the respective Invex gear meshes also produces frictional torques which contribute to supporting a torque division between drive axles. The respective friction forces at the Invex gear meshes may be represented as:

 

Fc , Fd = (F1 , F2) x (µ1)

 

The resulting frictional torques (Tf1 , Tf2) opposed to side gear rotation is related to mesh friction as follows:

 

Tf1 , Tf2 = (Fc , Fd) x R x Sin ø x Sin ß

 

where 'R' is the pitch radius of the respective side gears.

 

Therefore, the maximum difference torque which can be supported between drive axles is related to each of the above-equated frictional torques as follows:

 

T1 - T2 = Tf1 + Tf2 + Tf3 + Tf4 + (R / Rc) x (Tf5 + Tf6)

 

where 'Rc' is the pitch radius of the combination gears.

 

Letting the torque difference between drive axles (T1 - T2) be represented by 'Td', it follows that:

 

T1 = (Trg + Td) / 2, and

T2 = (Trg - Td) / 2

 

From this, the maximum ratio of torque which can be supported between drive axles (i.e., bias ratio) is expressed by the following proportion:

 

torque bias = T1 / T2 : 1

 

An alternative way of referring to drive axle torque distributions is by the term 'percent locking'. This term may be mathematically expressed as follows:

 

percent locking = (Td / Trg) x 100

 

Figure 6 shows the relationship between torque bias and percent locking over a range of comparable values of each.

 

S E CHOCHOLEK, BSME

Gleason Corporation, Rochester, New York, United States of America

In the Torsen, the gears pushed on each other during decel. They pushed on the case on accel. On the truetrac they push on the case on accel and don't get loaded on decel.

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Another thought:

If I'm right about flipping the gears, that may explain why people are wasting the washers. Instead of them getting squeezed on decel where the lockup is less or none, they're getting hit on accel...

 

Flip the side gears and the worm gears around and it should work the opposite way. Assuming you have it right and it is squeezing the gears together under accel of course...

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Another thought:

If I'm right about flipping the gears, that may explain why people are wasting the washers. Instead of them getting squeezed on decel where the lockup is less or none, they're getting hit on accel...

 

Flip the side gears and the worm gears around and it should work the opposite way. Assuming you have it right and it is squeezing the gears together under accel of course...

 

 

Bingo...what I was saying. But can you really just flip the gears? It's like putting a propeller on the boat backwards. The boat still goes forwards? No? lol

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This kind of ♥♥♥♥ always screws me up, so here's what I did. Saved your pic, opened it in Windows Picture Viewer, and flipped it 180 degrees. When you do this you can see that the gear patterns go the opposite way, so the side gears will drive the worms in the opposite direction.

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Holy Hopping Snot! I swapped the positions of the helicals and the side gears left to right and now the OBX thrusts OUTWARDS during acceleration! NOW it makes sense! This way it wont bash the washers when you punch the throttle. The only thing the washers will see is pressure from heavy engine breaking. I think this is the ULTIMATE solution to make the OBX function like the Quaife. Albeit probably not as smoothly and as durable but MUCH better than when the gearsets were backwards!

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I’ve been following this thread with great interest as I received my OBX (from Tuna Tom) late October. Upon disassembly I noted all the previously mentioned issues, Poor quality washers, burrs, dirt, etc. The bolts however were grade 12.9. Also mine arrived with the gears properly arranged, so if you do plan on using an OBX don’t just flip the gears assuming they are wrong. I’m guessing it comes down to lack of attention to detail during assembly at the OBX factory.

This next part is in regards to the machining tolerances of the OBX. My plan was to reuse the original ring and pinion in my R200. To help ease the set up of the ring to pinion, prior to pulling the open diff I checked the ring and pinion lash. It was between .006”and .0065”, (near the middle of the factory spec). After pulling the open diff and removing the ring gear I measured from the ring gear mounting surface on the diff to the two faces on the diff where the carrier bearing races seat. I then measured the same areas on the OBX and compared the numbers. The left (drivers side) was within .0005” (half a thousandth) however the passenger side dimension of the OBX was .012” smaller than the original open diff. Rather than try and order a new spacer ring from Nissan I cut an additional spacer from .012” steel shim stock and installed it along with the two original right side spacers. After reassembly the ring to pinion lash was now between .0055” and .006”. This may not be the best way to do it but it worked for me. Also I’m not sure if Nissan offers a spacer as large as I needed as the FSM showed spacer sizes ranging to a maximum of .007” larger than the spacer in my diff.

I hope this helps.

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Shims are shims and you don't need to use Nissan shims to get the diff set correctly. Cutting your own works fine. I would think that someone needing shims might go to a gear shop and find something close. MikeC has suggested that a 12 bolt chevy diff has shims that are pretty close in size, so that might be a first place to look, but most shops will have a big pegboard wall with different size and thickness shims, so it shouldn't be too hard to find something that works.

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I did not rearrange the gears in mine. All I did was change the washers. I don't remember the exact configuration. Mine had the same 12.9 grade bolts, and was also quite dirty right out of the plastic bag and box. I did my best to clean it when I installed the new washers. I changed the gear oil once in it so far, and it came out looking nasty (dark).

 

I will be taking it apart soon as I have a leaky pinion seal. I didn't replace the pinion seal when I put the LSD in (it was a junkyard R200). I'll post my findings.

 

In operation the limited slip action is quite good. I would say that it slips less than a Nissan CLSD, but not much. You can easily predict it's behavior during wheel spin. As far as noise, it make a fair amount of gear noise but no clunking. Using a solid or urethane differential mounts will amplify this I'm sure. I have a Ron Tyler/urethane mount in this car. Maybe different gear oil weights can quiet it down more.

 

Pete

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It looks like my OBX unit is going to be a drop-in with the factory shims that came out. I need to double check but so far I get about 0.005"-0.007" backlash on the ring gear. I also set the belville washers with about 10ft/lbs of initial break-away torque (preload). I just didn't feel comfortable setting zero preload for fear of gear rattles, or too much preload for fear of excessive wear, so I took a conservative approach. We will see how it works hopefully in a month or so. Snow melts.

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