How tough is the stock 9 inch do I need to go to the Daytona pinion

[Yeller]

I have and never found a difference. Advantage of working on race cars that get blown apart and examined with a microscope and reassembled.

with crush sleeve diffs, I've thrown a lot of .002" shims on them and reused them for a seal or yolk replacement, just retorqued and set up like a new one. I 100% agree that a solid spacer is the best, anything that I work on from scratch gets one. Repairs like a seal or yolk replacement no.

 

[jamesroney]

I have and never found a difference. Advantage of working on race cars that get blown apart and examined with a microscope and reassembled.

with crush sleeve diffs, I've thrown a lot of .002" shims on them and reused them for a seal or yolk replacement, just retorqued and set up like a new one. I 100% agree that a solid spacer is the best, anything that I work on from scratch gets one. Repairs like a seal or yolk replacement no.

I’m totally with you on WHAT to do, and I do the same. But I’m trying to reconcile WHY.
Why would you put a solid spacer in a 9 inch? (And I DO love those NASCAR boys that have select fit collars with no shims!) But the fundamental engineering advantage is lost on me. Yes, the collar thickness goes with the pinion support bearing bore depth. And yes, once you marry a set, they are super fast to swap.

You said that solid is better. I’m still not sure.

 

[Yeller]

Ok I'll delve deeper. as for a nascar application it may or may not be better their loads are constant and usually without major shock load. Drag racers hit them with enough shock load to actually make it crush past yield, destroying the bearings and gears. In a 4x4 off road application we are the hardest on crush sleeves, we put high torque loads in reverse, trying to suck the pinion into the differential. These loads are enough to crush the sleeve into a solid spacer, I've actually had them pressed to the pinion they were crushed so much. In a front axle application it does the same thing going forward. If you get a hop or bounce, your introducing shock load like the drag racers. The only solution is a solid spacer. For a shop that warrantees their work, its worth the few extra minutes and small extra expense to not have that come back with a failed crush sleeve, especially when there is a reasonable alternative. Does that make sense?

Back to the shifting to reverse...... We are horrible on axle shafts for the same reason. We get bound up, twist the axle until it begins to yield and holds some of that twist, a normal condition in drag racing, you paint a line down the length of the shaft and when it reaches a 360* twist you throw it away and replace it. We throw the curve ball, twist it until it begins to yield and then put it in reverse and do it again. Now your not just working the molecules in 1 direction making them pull on each other and stretching, your twisting it the other way causing those molecules to begin to fracture, eventually leading up to a broken axle, often in a situation that it should not have broken, all breaks down to accumulated stress.

 

[ntsqd]

..."you can simply replace that bearing without having reset the spacer's length to again have the desired preload." 100% agree.

I remember in Strength of Materials that the bending of a tube versus the bending of a tube with a tension memeber resulted in greater resistance to bending when the material is anisotropic. So yes, a pre-stressed concrete beam has increased resistance to bending. But I'm not so sure about a pre-stressed carbon steel pinion.

But that's kind of moot since the pinion nut torque and clamp load is the same for both crush collar and shim, and therefore the tensile stress is identical for both.

What am I missing?

The example that we worked was a steel tube with a tensioned steel rod at it's center, not pre-stressed concrete. Mine was an applied Strengths class that was Trig based, not the typical ME's class that was far more theoretical and Calculus based. Oddly enough I got it from the Construction Management curriculum rather than the ME curriculum.

What you're missing is that the crush sleeve has been yielded and will continue to yield long after you've stopped applying torque to the pinion nut. It hasn't been taken to the max possible loading like a torque to yield head bolt, it's been taken well beyond that point.

I crushed one further in an 8" with ~26" tall tires using a carb'd 302 with 3.80 gears in a ~2700 lbs '67 Ranchero. It's worst case use was flat towing the avatar, all ~1500 lbs of it. The p/n for the sleeve is the same for both the 8" and the 9", so the rebuild got a spacer.

On the Reversing of torsion topic, 300M was developed specifically for this type of application. It was one of the reasons why, when I was asked what alloy to make the first aftermarket HD D20 output shafts from, that I suggested it. I guess mine was a good suggestion since that's what they were made from.

 

[jamesroney]

Ok. Steel tube with a tension rod I understand. Compressive forces on the tube prior to applying a bending moment would certainly allow for a greater load capacity on the bottom of the tube. My Management Engineering degree was production and operations focused, and my Mechanical Engineering degree was indeeed…theoretical.

But back to your 8 inch and the crush sleeve. Are you telling me that you managed to apply an axial load on the gear head that was sufficient to overcome the tapered bearing, push thru the cone, compress the cup, compress the housing…and push against WHAT to crush the collar? Can’t be the outer bearing, because all loads are pushing out. That makes no sense.

The only way that the crush sleeve gets shorter is if the two inner bearing races get closer together. There is no static load, and I’m not sure if there’s a shock load that can push to make the crush sleeve shorter.

I’m not saying that you can’t overcrush the sleeve with the nut, and I’m not saying that shims can’t get squished out. (I’ve seen them…) All I’m saying is I don’t see how.

 

[jamesroney]

Ok I'll delve deeper. as for a nascar application it may or may not be better their loads are constant and usually without major shock load. Drag racers hit them with enough shock load to actually make it crush past yield, destroying the bearings and gears. In a 4x4 off road application we are the hardest on crush sleeves, we put high torque loads in reverse, trying to suck the pinion into the differential. These loads are enough to crush the sleeve into a solid spacer, I've actually had them pressed to the pinion they were crushed so much. In a front axle application it does the same thing going forward. If you get a hop or bounce, your introducing shock load like the drag racers. The only solution is a solid spacer. For a shop that warrantees their work, its worth the few extra minutes and small extra expense to not have that come back with a failed crush sleeve, especially when there is a reasonable alternative. Does that make sense?

Back to the shifting to reverse...... We are horrible on axle shafts for the same reason. We get bound up, twist the axle until it begins to yield and holds some of that twist, a normal condition in drag racing, you paint a line down the length of the shaft and when it reaches a 360* twist you throw it away and replace it. We throw the curve ball, twist it until it begins to yield and then put it in reverse and do it again. Now your not just working the molecules in 1 direction making them pull on each other and stretching, your twisting it the other way causing those molecules to begin to fracture, eventually leading up to a broken axle, often in a situation that it should not have broken, all breaks down to accumulated stress.

Pulling on the pinion does not apply any force to the crush sleeve. The pinion pulls on the yoke which pulls on the bearing cone, which tries to shove the cup into the housing.

Low pinion D44 pulls on the pinion in forward.

Totally agree on the rear, except when you launch a 9 inch hard, it will blow the pinion support right out of the carrier. (You can find it hanging on the end of the driveshaft…). But the crush sleeve will be perfect!

Put a 9 inch pinion into a Daytona pinion support, and try pressing the pinion out the front. Or drop a pinion into a d44 housing, and try to push it out the front. The pinion preload pack only gets looser.

 

[jamesroney]

I was thinking that too paul
if you run a lift and 6 degree shims, it looks like you will be putting in less gear oil in the axle because of the angle, the oil will leak out or be level with the fill hole earlier. Unless you put more oil in before You put the axle in.

SPAP, sorry for the previous thread jack.

The oil level is established by the fill plug. All 9 inch axles since about May 15 of 1967 fill thru the case. If shim the perches, and elevate the pinion...the fill port rises relative to earth. So in order to fill it...you have to add MORE gear oil. I've seen rear ends with a 15 degree pinion inclination (from horizontal) that take over a gallon to fill. You can imagine that if you pointed your pinion straight up...then it would take the most oil to fill it. If you point the pinion straight down...that would be the least.

If you are going to stay with 31 spline axles, and you are going to run a true-trac...then your original C7AW-E case with the small pinion support will last longer than the true trac.

the 9 inch was used in countless 1/2 ton pickups, vans, and Ambulances from 1957 to 1988. By the time they received the 31 spline axles, they reached maximum strength and durability. In stock form, and with an automatic transmission...it will push that Bronco of yours around for a million miles. Sure, a Nodular case with a Daytona support is "better." But some of the guys on this thread hit the trail pretty hard.

If you bring yours to me here in Fremont, CA... I'll put it together for free. Just buy the parts and bring beer.

James.

 

[ntsqd]

A bending load on a rotating shaft would crush the sleeve further. Likely that means that the case was also elastically distorted under the load. No bloody clue how I could have achieved that kind of loading in the Ranchero. It is also possible that the Heat-Treat of that particular crush sleeve was off, and it was easily yielded further. I'd have thought that the guy who assembled it the first time would have felt that, but maybe not.

It wouldn't take much to loose the pre-load. I once set-up seven 50's era Fiat Otto Vu rear diffs (~2.5% of all known to exist). These have a pinion bearing spacer and the difference between no pre-load and a spot-on pre-load was as little as .001" difference in the length of the spacer. (We used a surface grinder to adjust the spacer lengths.) In a 9" I'd expect it to be a bit more of a length delta, but even if it is double that still isn't much distortion.

It isn't the removing of the yoke that is the problem with a crush sleeve, it is the replacement of it. It is now not long enough to establish the previous pre-load due to it's elastic deformation. The plastic deformation has shortened it too far to achieve enough elastic deformation to create the needed pre-load and because it is designed to crush it can't behave like a solid spacer.