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Discussion Starter #1
Set up my first 9" a few weeks ago, and I'm finally getting around to to finishing it off by setting the pinion bearing pre load. I'm using a solid shim spacer. Looking around the interwebz I have found a few guys that claim with a solid spacer not to run any pinion bearing pre load because the spacer wont "absorb heat" like a crush sleeve will, and can actually expand enough to cause damage to the pinion bearings. Anybody heard of this or had this experience themselves? I already have it set up with the pre load in spec of what it should be with a crush sleeve, but it's still out the truck and easy to change if need be.
 

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From what I've read you are not supposed to preload the bearings with a solid spacer. I remember doing mine and setting it up to have .0005"-.0010" of endplay. I don't remember where I read that but I believe it was on a Mark Williams forum or something. I hammered my 9" with 39.5" iroks for over a year and never had an issue.
 

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Discussion Starter #4
From what I've read you are not supposed to preload the bearings with a solid spacer. I remember doing mine and setting it up to have .0005"-.0010" of endplay. I don't remember where I read that but I believe it was on a Mark Williams forum or something. I hammered my 9" with 39.5" iroks for over a year and never had an issue.
That's the same thing I read too. I'm new to differential set up, so I figured I'd check it out here and see what people had to say.
 

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Intentional pinion end play? This I gotta hear.
Yup, intentional. The theory is that if you preload the solid spacer the same as you would a crush sleeve it would expand and grow with heat, thus causing more bearing preload, and in turn more heat .....

edit: I am not a differential specialist, and this may be the completely wrong way of setting it up, but, I did it this way, and it worked flawless. Maybe I got lucky. I'd like to hear some input from guys that do this kind of stuff for a living.
 

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If the spacer expanded, wouldn't it put the bearings further apart, thus reducing preload?

My initial reaction is one of disbelief, but I am trying to be open minded. Hopefully someone has strong info on the subject.

Most of the Mark Williams stuff I have worked with was ball bearing, and the spacer was specific to the pinion support. It was preset and didn't require adjustment.
 

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If the spacer expanded, wouldn't it put the bearings further apart, thus reducing preload?

My initial reaction is one of disbelief, but I am trying to be open minded.
YES!!! you're right. Like I said I don't really remember where I read it, or if the way I explained it was correct (clearly it wasn't), but I know I did read a lot about it a few years ago and I ended up doing mine that way. I set it up to have a half a thou end play. I wish there was more info out there on the solid spacer route.
 

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I've always set them up with normal preload, 13-20in lbs. with new bearings on the 9" and they work great. Lighter with used 5-8in lbs.
 

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Discussion Starter #9
If the spacer expanded, wouldn't it put the bearings further apart, thus reducing preload?

My initial reaction is one of disbelief, but I am trying to be open minded. Hopefully someone has strong info on the subject.
I feel like a tard now for not realizing that's exactly what would happen. Leave it to somebody with a clear mind to come and state the obvious. Looks like I'll be running it the way it is.
 

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I checked my Ford shop manual (1974 Truck edition) which says the F100 with 390 and manual trans came with a solid spacer from the factory. Set pinion preload to 12.5 - 32.5 in-lb.

Always start with the largest spacer and work down. Too small a spacer with the required pinion nut torque could damage the bearings.
 
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