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PostPosted: Tue May 01, 2018 5:56 am 
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kfreiheit wrote:
blamkin86 wrote:
Not sure how you could possibly know that the spacer was exactly the proper height for your R&P and case combo.

Snake oil to me; let's see what Jesse says...


There is a solid spacer and stack of shims. You assemble with all the shims and then check end play. Remove shims until endplay is correct. Then you do a post check of drag on the bearings like the fsm states. In my opinion i think it should feel and act exactly like a crush sleeve in 99% of usage.


That makes a lot more sense, thanks. I guess if you aren't good at the crush washer stuff, it would be nice to be able to take it apart until you get it right.


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PostPosted: Tue May 01, 2018 7:49 am 
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How is that different from the crush washer? You still have to set the rotational torque with no seal and then remove to final assemble. So many myths about this stuff. I have done more than a hundred of the various Mazda diffs over the years with the factory parts with zero issues. This includes cutting them in two pieces and welding them up for a second gen so we have gear choices. Do it right once and it will last a long time. A crush washer is just a spacer after initial install, they do not move if you disassemble the diff. Put a set of mics on it and it will check the same as the solid sleeve when setup correctly.


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PostPosted: Tue May 01, 2018 12:02 pm 
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Steve Eckerich wrote:
How is that different from the crush washer? You still have to set the rotational torque with no seal and then remove to final assemble. So many myths about this stuff. I have done more than a hundred of the various Mazda diffs over the years with the factory parts with zero issues. This includes cutting them in two pieces and welding them up for a second gen so we have gear choices. Do it right once and it will last a long time. A crush washer is just a spacer after initial install, they do not move if you disassemble the diff. Put a set of mics on it and it will check the same as the solid sleeve when setup correctly.

Steve, my take is that the theory behind the crush washer is that it's "somewhat" flexible by nature. You crush it to set the total length, but it can still be crushed more or deformed somewhat by repeated hammering of the rear end, causing the crush sleeve to deform and loosen.. I'm hearing both sides of the story for those for and against it, and it falls under "plausible but unlikely" to me.

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Houston Region
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PostPosted: Tue May 01, 2018 12:24 pm 
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Matt93SE wrote:
Steve Eckerich wrote:
How is that different from the crush washer? You still have to set the rotational torque with no seal and then remove to final assemble. So many myths about this stuff. I have done more than a hundred of the various Mazda diffs over the years with the factory parts with zero issues. This includes cutting them in two pieces and welding them up for a second gen so we have gear choices. Do it right once and it will last a long time. A crush washer is just a spacer after initial install, they do not move if you disassemble the diff. Put a set of mics on it and it will check the same as the solid sleeve when setup correctly.

Steve, my take is that the theory behind the crush washer is that it's "somewhat" flexible by nature. You crush it to set the total length, but it can still be crushed more or deformed somewhat by repeated hammering of the rear end, causing the crush sleeve to deform and loosen.. I'm hearing both sides of the story for those for and against it, and it falls under "plausible but unlikely" to me.

Agree. If you have a dog ring box, solid mounted everything, it will bang the diff pretty bad over time. I have just never pulled one apart that had the crush sleeve beat down past the normal clearance. I guess it could happen, but the taper bearings will be gone long before that happens. Keep in mind as you accelerate it pushes against one of the taper bearings for thrust load while unloading the other taper bearing. Decel and it pushes against the other with same effect. Never will be a time that both bearings are being loaded at the same time to crush it. Side loading of the pinion will push both taper bearings out, not in.

Either way if it works go for it. We made a run of the fixed sleeves in the early 90's and went back to crush sleeves. No shims, we just ground them to exact fit on surface grinder.


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PostPosted: Wed May 02, 2018 12:29 am 
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Interesting stuff. For what it is worth one of the guys that works for me worked at a 4WD-Offroad shop for 7-8 years. He can tell you about every axle swap you can do on a Jeep or Toyota etc and he can look at an axle and tell you what it is from 50 feet driving down the road as those guys are all about the axles and driveline upgrades and swaps. And he has done about 200 setups. I asked him and he had used the spacers on some setups but said it did not really help much since every differential has a weakest link that will break and those off road guys will find what it is. But that it was never related to the crush sleave.

He did his first Mazda 1.8 Miata (same as 79-85 RX7)and he was really impressed by the design. Easy to do but strong and well made.

We had one 5.11 Ring and Pinion last 2 logbooks with a lot of endurance racing including a 24 race at Nelson when the track was super rough and full of unavoidable bumps. The joke was that there was the fast line and then there was the line that did not break the car. We replaced it because a rear bearing backed out at Road Atlanta and pushed the seal out and emptied the rear axle of oil. It was bone dry. And even then we refilled it and did the rest of the weekend on it. At that point it had around 10K race miles on it.

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PostPosted: Wed May 02, 2018 7:38 am 
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Steve or anyone else who has done these,
Any tips or tricks? I made a slip fit pinion bearing to setup the pinion depth with the other pinion spacer/washer How often is the depth off that you need to order another spacer/washer?

Kyle


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PostPosted: Wed May 02, 2018 10:47 am 
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Mazdaseven wrote:
Interesting stuff. For what it is worth one of the guys that works for me worked at a 4WD-Offroad shop for 7-8 years. He can tell you about every axle swap you can do on a Jeep or Toyota etc and he can look at an axle and tell you what it is from 50 feet driving down the road as those guys are all about the axles and driveline upgrades and swaps. And he has done about 200 setups. I asked him and he had used the spacers on some setups but said it did not really help much since every differential has a weakest link that will break and those off road guys will find what it is. But that it was never related to the crush sleave.

He did his first Mazda 1.8 Miata (same as 79-85 RX7)and he was really impressed by the design. Easy to do but strong and well made.

We had one 5.11 Ring and Pinion last 2 logbooks with a lot of endurance racing including a 24 race at Nelson when the track was super rough and full of unavoidable bumps. The joke was that there was the fast line and then there was the line that did not break the car. We replaced it because a rear bearing backed out at Road Atlanta and pushed the seal out and emptied the rear axle of oil. It was bone dry. And even then we refilled it and did the rest of the weekend on it. At that point it had around 10K race miles on it.


the 4.88 has been in this car for quite some time- I've filled maybe half a logbook since I've owned this car with the 4.88 and now running my 5.1 the last few races since I killed the 4.88. At a couple tracks around here I'm above 8500rpm in 5th with the 5.1, so it would be good to get the 4.88 back together for those tracks.

Given the other reliability issues I've had with this car, I'm looking for anything I can legally do to help keep the car together better. sounds like this is a moot point really, as others have stated this doesn't seem to be the root cause of failure.. BUT not knowing what killed it and the price I'm paying to replace it, $50 is small dollars.

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Matt Blehm
Houston Region
EP 1st Gen RX7
STU Nissan 240SX


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PostPosted: Wed May 02, 2018 9:24 pm 
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We just used this product on a 400rwp S2000 Honda. The Honda diff is very similar to the NB+ Miata unit and in fact we used a 4.10 Miata R&P. The Honda likes to break the caps holding the diff in place.

I had called Weir about making and installing billet caps for the Honda diff and he explained to me why this product would be all I needed to use. Anytime a vendor talks me out of spending $$$ at his shop I am willing to listen. The spacer kit made setting up the diff a breeze with no worry about too much or too little crush.

Don't get me wrong, I have never had a diff in a Miata/RX7/RX8 fail using the crush sleeves. I just like the fact that the Weir part is reusable and easily repeatable... YMMV...


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PostPosted: Wed May 02, 2018 9:58 pm 
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I completely understand where you are coming from. Nobody wants to have something break. And That is why I said it was a good post. I learned a lot and I never would have asked my guy about it until you asked about it here. Until you asked about it I never knew they made them.

And You make a lot of power and run slicks. We had 125 WHP. And we also had the clutch LSD rebuilt several times and the guy who did them for us then would check the setup when he did that. So he could have been adjusting the shims for the pinion or changing out bearings. We eventually started doing that ourselves and even made an axle with socket welded to the end so we could check the torque point where the LSD would slip. I also remember the housing having extra baffle plates and a second filler plug higher up. Maybe that helped it too.

In my Production car I have a Kia 4.78 I purchased used on Ebay for $135 that I did myself. It was a temperary one I did so we could make an event while a pro was dong the "good" one. Which is now the spare but really should be the one in the car.

One thing Mike Van Steenburg said when I ruined my FP Miata one when I knocked off the oil cooler tank going through the sand swales at Roebling was to not reuse the carrier. The pinion teeth had actually melted and looked like plastic that had been burned. So did one of the pinion bearings. He said when they get that hot he had the next one fail and did not reuse the carrier when he saw pinion bearimgs that had run dry and melted.

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Rob Garrison

FP Mazda Miata
IT7 RX7
2nd Gen STL EP RX7


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