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OBX vs Quaife (with pixors)

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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.

Did you check for slop as reported by 75&78Z? You don't want that slop in there, in fact you want the carrier to be hard to get into the housing because it's such a tight fit. Ideally it would be "have to smack it with a dead blow to get it in tight".

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With mine we had to order the correct shims from Nissan. They are cheap BTW. Without the correct shims there was too much slop, and the ring gear bolt heads just barely rubbed the pumpkin. Make sure the carrier rotates freely through a full rotation. With the stock shims mine rubbed on two of the ring gear bolt heads.

 

Pete

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I got unlucky in that the internal OBX gears were backwards but I got lucky in that the OBX measured within 0.001 to all the width and ring gear location to the original open center. Yes the OBX needed to be coaxed into place with a mallet. There are no bolt head interferences....yet!

 

BTW here is the McMaster Part for 12mm to 10mm bushings for the ring gear bolt adaptors. 10 needed. 6679K14 http://www.mcmaster.com/nav/enter.asp?partnum=6679K14

 

 

On another note. I had my dad apply torque to the input shaft of the diff while I tried to turn the side shafts in opposite directions. It works. I could not break the breakaway torque with two long screwdrives wedged in the stub axle studs, when my dad applied input torque. Pretty cool.

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I took my OBX apart tonight, and confirmed that the gears are arranged like this photo of a Quaife unit:

 

F23.jpg

 

Not the way cygnusx1 unit came:

 

462493812_DaVQP-S.jpg

 

Please confirm that I am correct on this.

 

The washers are in perfect shape. Little to no wear after one season of street driving, and a couple track days.

 

I have my washers arranged like this: ))))((((. There is at least one washer of preload in this configuration.

 

Pete

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Pete great to hear. You are correct with your photos. The lower photo is how mine arrived wrong! How do the rest of the internals look as far as wear?

wow when I spotted the pics from Pete about his OBX and your talk about how yours was assembled incorrectly - it had me thinking if my unit was wrong too. Now given I was one of the first - if not the first to get one of these on Hybridz and give it ago - however my car is still off the road and all I have done is assemble the unit into the diff and paint it ready for the body to get back from the body shop......

 

Anyway I went back to the old threads see here http://forums.hybridz.org/showthread.php?t=107997&highlight=obx

Back in 2006 - time just flys

 

Anyway I found my pic of the unit I got and how it was assembled. You can see the difference vs the one from Pete.

462493812_DaVQP-S.jpg

OBX_HLSD_1.JPG

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Guest primovera

Hello, I'm new to this discussion but I have a 1973 240z with what im guessing is a r180. Will the OBX fit in my car? If it doesn't fit does anyone have a money saving solution for a lsd for my application. Thanks

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i installed the obx in my 85 300 zx turbo a couple months ago and have the ckunk in it. after finding and reading this thread i cked the diff today. when i turn the driveshaft foward you can tell it pulls the axel stubs inward, and turning backwards pushes the axels out! dang it the gears must be in backwards.

i see lots of disscussion on replaceing the spring washers. but where do you get them? i want to get new ones here before i pull the carrier out.

 

thanks for the great wright up and info!

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OK I drove the car for about 20 miles since all of my upgrades including the OBX. I can tell you that the OBX definitely drives both wheels under power. You can feel the tires biting at the road instead of one just breaking loose like it used to. The car turns in just as good as it did before. During normal driving, you wouldn't know anything changed. The only thing you notice is a clunk when going from decel to accel. It's a pretty loud metallic thump in the rear. (I am using the RT mount) I am almost positive now that it comes from the backlash in all the internal OBX gears, and from the free-float movement of the "barber-pole" gears around the perimeter of the OBX. When you go from decel to accel, all the planetary gears need to shift in their pockets from outside to inside. If I remember correctly, there was about 1/8"+ of side play in those gears. In retrospect, I might have measured the exact side to side clearance of those gears and dropped in a bellville washer on the outer ends of each one, to preload them to the accel side. This in theory would eliminate the majority of the accel/decel slop in the differential. The downside is that the washers would act sort of as little clutches and may wear out....then again, maybe they would hold up, since they only work hard when the wheels are spinning at very different speeds, which is almost never.

 

The idea is to preload the center gears OUTWARDS and preload the perimeter gears INWARDS.

 

Go ahead and grab your OBX unit. Shake it, you will hear the perimeter gears rattling in their pockets. They have no preload and are free to slam back and forth due to excessive clearances.

 

This is why the OBX is a low cost unit. It works, but with a price.

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Dave,

 

It sounds like ring and pinion gear slop to me. Did you check the lash in the ring and pinion before and after replacing the differential? With mine, we had to re-shim the carrier to reduce the ring and pinion slop and to prevent the ring gear bolts from rubbing the differential housing.

 

Mine makes some gear noise (not a continuous whine), but has minimal clunk when getting on and off the throttle. I have the RT mount in there too.

 

Can you feel any slop if you rotate the drive shaft while holding one of the half shafts?

 

Pete

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Can you feel any slop if you rotate the drive shaft while holding one of the half shafts?

Measuring backlash at the pinion is different than much different than measuring it at the ring gear due to the pitch of the teeth. The pinion gear might have 1/4" of movement and the backlash at the ring gear might still be .005". I've seen this mistake quite a few times when guys are trying to diagnose their clunk. In fact there was a guy on classiczcars.com not too long ago that did the same thing. I warned him that the backlash was probably fine, he ended up buying another diff. He tested the backlash in the "good" diff the same way and found the same "large" amount of slop measuring at the pinion. Holding one of the shafts and turning the pinion will work the gears inside the LSD, so that is not a good way to test backlash in my opinion. Even holding BOTH outputs and spinning the pinion will work the LSD before the outputs move. All you can really do is try to carefully feel when the pinion hits the ring, but that's hard to do because of the pitch of the teeth.

 

You checked backlash when you had the carrier out. Assuming the carrier was tight in the housing, I think backlash is not your problem. I also think that the more rigid the mounts are the more clunk you'll hear from an acceptable amount of backlash, and that at some point we'll all just have to get over it and deal with the fact that our diffs don't have fluid filled mounts to isolate all the NVH from the chassis.

 

As far as the noise being from the helical gears, I'm doubting that this is correct too. On the true-trac units there are no springs at all, and the common noise complaint is a crunching sound from those (I think it is all the little helicals moving around and hitting the case inside one after the other).

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- The backlash at my ring gear was about 0.005" checked in the same manner as the factory manual. With a dial indicator on the edge of a ring tooth with the pinion clamped.

 

- The satellite gears in the OBX will kick back and forth in their bores in response to decel/accel. That's the whole key to a torsen diff. The OBX allows quite a bit of room for these to move.

 

-There is quite a bit of lash in between the center barrel gears and the satellite gears. (just shake the OBX unit and listen). I did not measure this lash but it's there. If I hadn't preloaded the center gears, I would be able to feel the lash by turning the half shafts forwards and backwards together.

 

-The fit of my 280ZXT half shaft splines into the OBX is also somewhat sloppy and is part of the clunk I hear. I don't see any wear on the splines. The original stubs were also sloppy in the OBX, BUT they were also sloppy in the original diff center. So I don't think it's unusually loose CV axle splines at the diff. Make sense? Basically I don't suspect an unusually loose spline because that play has always been there with both diffs and both axle types.

 

 

I am going to setup the camera in the car tonight and try to capture the sound. The gear noise is wonderful while driving along steadily. Just a distant whine of diff gears, like a good classic sports car should have. The clunk is a bit unnerving and it makes me self concious of my shifting. I have to be so precise with my rev matching so I don't get the clunk treatment.

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At about 1:10, I was climbing a pretty steep hill so there was a good load on the rear end. You can clearly hear the normal gear noise at that point. At least, the gear noise seems normal and expected with poly mounts all around. If you've ever been in a solid mounted diff car, you know what gear noise sounds like. The OBX is what I think is making the clunk. I am going to borrow some CV shafts from EvilC to eliminate that possibility. The humming is probably from slightly wavering backlash around the ring due to machining tolerances of the OBX.

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I think your right. It sounds more like the OBX than the R&P. It more like a clack, than a clunk (technical terms :mrgreen:).

 

The mechanical noise you are hearing is the same noise I have. The Nissan CLSD is quiet, the OBX is noisy for sure.

 

I've driven a car with the Quaife, and it is quiet BTW.

 

Pete

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