OBX vs Quaife (with pixors)

[batou]

here yah go

[V8INtheZ]

here yah go

 

 

Good call dude

[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

[automec]

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!

[cygnusx1]

Spacers Here:

 

http://forums.hybridz.org/showpost.php?p=982194&postcount=54

 

Washers:

 

http://forums.hybridz.org/showpost.php?p=786643&postcount=13

[cygnusx1]

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.

[z-ya]

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

[JMortensen]

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).

[cygnusx1]

- 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.

[rags]

Dave,

 

FWIW, my Gleason makes the same noise and has the same play. I find it very annoying. Man I must be getting old

 

 

Joe

[cygnusx1]

Here is a video I took this afternoon. Listen for me getting on and off the throttle to demonstrate the clunk. It sounds much more like a pop in the video. It's a much deeper clunk than it sounds in the video.

 

[JMortensen]

That does sound loud.

[Careless]

I hear a humming sound too.

[cygnusx1]

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.

[z-ya]

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

 

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

[cygnusx1]

I am strongly considering pulling out the OBX and adding bellville washers to the smaller gears outside ends. If there is no space inside the bores for the washers, I'll have the ends of the gears ground down a touch, to make room for a preloaded bellville washer. This should take the majority of the CLACK out of the diff.

 

The main gears are held preloaded OUTWARDS, but the planetary gears are free floating(within their loose bores), and knock side to side on accel/decel. With bellville washers on their outer ends, they would preload in the accel direction, so when you lift off the throttle, they would remain in position, ready for accel again.

 

The only downside is that the initial breakaway torque would increase. Right now it's only about 15ft-lbs. I guess it would be about 30-40 after adding all the other preload washers. Still in acceptable range.

[JMortensen]

I am strongly considering pulling out the OBX and adding bellville washers to the smaller gears outside ends. If there is no space inside the bores for the washers, I'll have the ends of the gears ground down a touch, to make room for a preloaded bellville washer. This should take the majority of the CLACK out of the diff.

I don't like this idea. This would grind the gears on the belleville springs under load, something they apparently don't take too kindly judging by the problems people have when they have the side gears installed backwards.

 

You're sure you can't put some kind of place holder in on the other side of the worm gears? If not a Belleville spring, maybe just a solid shim would work. Preloading might completely eliminate the noise, but I think a solid shim that took up the majority of the slack should significantly reduce it.

[cygnusx1]

The bellville springs in the center grind against the two side gears all the time when there is wheel speed difference. There is no load on them during positive traction other than the assembly pre-load. The same would apply to washers on the outboard ends of the little gears. They are driven into the pocket faces during positive drive, not into the washers. All of the washers would see compressive force only during snap-decel or heavy engine breaking. Normal street driving would stress them very little. Even hard acceleration would have no effect on the washers. They are on the "downstream" side.

 

OTOH, yes, a brass spacer, thrust washer would work well instead of the bellevilles, if sized precisely to each pocket-gear space.

[JMortensen]

All of the washers would see compressive force only during snap-decel or heavy engine breaking. Normal street driving would stress them very little. Even hard acceleration would have no effect on the washers. They are on the "downstream" side.

I thought they were driven towards the outside of the case. If I'm wrong, then go for it.

[z-ya]

Dave,

 

I drove my car for the first time this year the other day. I definitely do not have the clunking sound you have. I can get on and off the throttle without clunk. What I do have is a gear noise that I can control with the throttle. Under full load there is no noise. Only when cruising can I make the gear noise my modulating the throttle just the right way.

 

I wonder if a heavier oil might quiet yours down. I'm using 75W90 conventional in mine.

 

Pete