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OBX vs Quaife (with pixors)

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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.

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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.

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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.

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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.

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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

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I don't know if the clunk in mine is an anomaly or if it's normal for the OBX. I can tell you that it certainly made a big difference in accelerating out of corners, and launching the car. I feel like I can steer it with my right foot when the car is rounding a nice tight curve. It works as an LSD. Under "grocery" driving, it is transparent other than the clunk. I like it. I would love it if the clunk were gone. Worth the money? Yes. But if you got the dough, go for the Quaiffe if it doesn't clunk.

 

EDIT!

 

I got under the car tonight because I need to use it for work tomorrow. I lay on my back and rolled the car in gear, back and forth over myself. I watched the car roll back and forth about 5" just on the driveline slop. But I noticed that the diff was rocking ever so slightly left to right. I checked the mustache bar bolts up top and they were good, but one of the rear cover mount bolts was slightly loose (could be stripped in the cover) and allowing some movement! I torqued it down and the car still rolled back and forth about 5" but the clunk was GONE! I drove it and for the first time in all of my life, I drove a Z without a clunk in the rear. There is still slop in the drivetrain but it's more of a springy feel (not bothersome at all) and NOT a clunk.

 

Retrospect:

This car has had a clunk since 1989 when I bought it. I changed the diff twice, the axles, the trans, the rear bearings, all the mounts, all the bushings....and it still had a clunk. I lived with it. This past Winter, I changed it all again, with an OBX, and an RT Mount, tranny, but the clunk was still there. :-( Since I had even expected the clunk to remain, I failed to even explore the obvious.

 

Moral:

Check everything again....and again. Don't assume. Driveline slop does NOT equal CLUNK sounds.

 

 

I can now wholly recommend the OBX unit. Based on my limited use, and Pete's more extensive use. It works, and seems to hold up.

 

:mparty:

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Dave,

 

Those bolts loosen up on me too. Typically after I swap the diff, and after few hundred miles, I need to tighten them back down. 300ft-lbs at the wheels tends to move things a round.

 

Is the gear noise you hear similar to what I described?

 

Thanks,

 

Pete

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Oh yeah the gear noise is....gear noise. Sounds kind of like the onboard videos of the rally cars. It varies with engine load and vehicle speed. I like the gear noise. It's not really loud. It's just there. If I crack a window open, the wind noise drowns out most of the gear noise. I don't have a radio. I don't think the gear noise is much different than a standard diff would be with an RT mount and poly bushings. I never had the RT mount with a stock diff. When a wheel comes off the ground, and the diff opens up, you can hear much more of the gear noises. I only get that when pulling up my steep driveway. One wheel will sometimes lift off the ground from the severe angle.

 

Maybe those mustache bar bolts call for some locktite...

 

I am making close to, if not, 350ft-lbs. I only have about 1000 miles on it but Pete has a few more. I think it will hold up fine.

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Downloaded.

 

Yup I have no desire to go through that pain. I'll pay someone to do it.

 

Thanks!

 

 

Should any transmission shop have the proper tools to put it in?

You only need to mess with backlash when installing an LSD. It's really pretty easy. Look in the yellow pages for gear or drivetrain shops. I think some transmission shops do rear ends, but pretty much every town has a gear shop.

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OBX is now offering the 'lifetime warranty' hook as well, predicated on the condition the diffy unit is not disassembled.

 

With a warranty, regardless of application, it takes a step up in the competiton.

 

Loosing your car for a time while the replacement is coming can suck, but that would be the same with Quaife or OBX.

 

My 73 with a conventional LSD also has had issues with the rear cover bolts coming loose no matter what I seem to do to it. Maybe the 265's out back and my right foot have something to do with it...

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I guess you need to determine if your gears are installed backwards, courtesy of OBX, without opening it up, or you void your warranty. Hmmm.

 

I emailed them about what I found in my OBX, and linked them to this thread, but I never got a reply from them. I guess my warranty is officially expired. LOL.

 

You get what you pay for in general, but at least with this part, you can rework it if you have to, and get a decent performing part at a value price.

 

This is the unit that is in my R200 3.54

462491630_UPXnh-XL.jpg

462491738_dqj3R-XL.jpg

462492149_Tbgfh-XL.jpg

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How do you determine the gear ratio of the OBX unit? Or should I say is there anything to take into consideration when trying to setup the over all car gearing? Ex. Car "a" is running World Class T5 with stock gearing powered by stock lt1-- would the OBX unit compliment overall gearing?

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The OBX unit uses whatever ring and pinion from an R200 that you want. It won't effect your gear ratios. You pick the ring you want to bolt onto it. Usually, you use whatever ratio is already in the rear. Re-gearing for a specific application is another topic alltogether.

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I'm going to vouch for the OBX diff. I just recently finished installing a unit in my R200.

 

The packaging was that off an old surplus AK-47 with oil all over place and had the same smell as my old Russian rifle. It does require a bit of cleaning/wiping but the overall exterior finish isnt bad. Mine came with 12.9 grade bolts, and was assembled the correct way. I did however, replace the thinner bellville washers with the Mcmaster carr ones. After taking the whole unit a part and putting it back together I was so shocked not only how simple this type of differential works but how easy it would be to machine/produce. I really don't know how quaife sells their units for $1,400+.

 

IMO this unit is way too simple to be expensive. As long as the manufacturing processes are legit it's really hard to screw this up.

 

Anyway, after torquing everything to spec and topping the carrier off with 75w90 I tried to spin one wheel and noticed there was quite a bit a pre-load with the thicker washers. Drove the car around the neighborhood a bit and it felt exactly like an open diff. I was able to make very sharp turns without feeling any scrub from the inside wheel, even tight circles no problem.

 

Went for another spin and easily laid two fat strips down. I tried diving into a corner without braking and the car turned in just like an open diff then stomped on it mid corner and the rear pitches out as if it had a locker. This type of differential is truley awsome.

 

I only installed the OBX unit and nothing else. I didnt notice any additional, clunking, popping, whining, or anything like that. So far it operates really smooth without a flaw.

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