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Pinion Bearing Preload and Drive Shaft Install

vavaroutsos

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I installed new Adams drive shafts yesterday. Before touching the rear pinion nut I measured the pinion total torque to rotate and it was only 15 lb-in. I installed the new yoke and ran the pinion nut down with the impact wrench. I could feel it bottom and gave it a few more hits with the impact. I checked the pinion torque to rotate again and it was about the same. I couldn't feel any play in the pinion other than rotational backlash. The Dana specs for the Advantek 44 call for quite a bit more torque than this:

PTR: 13.54 - 21.42
PTTR: PTR plus 8.43 - 15.94

Is there this much difference between new bearings that have not been oiled and broken in bearing in oil? What have others measured for PTTR when installing new drive shafts. What signs should I look for that indicate too little pinion bearing preload?
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roaniecowpony

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Pete, I believe they should be the same rotating torque whether installing new or used bearings, at the time of installation. I haven't specifically worked on a Dana, but other GM and Ford diffs. Diffs that have a crush sleeve between the 2 pinion bearings, will increase rotational torque only upon crushing the sleeve further. So, if you disassemble, or loosen the pinion nut, when you tighten it down again, it will have the same rotational torque as before, until you start to crush the sleeve further. That takes more torque on the nut than most people imagine. I would not use an impact to to that. You really want to feel the nut rotate. It's a fine line between not enough rotational torque and too much. We're talking very small amounts of rotating the nut with a long bar, then checking, repeat. If you go too far and the bearing has too much drag (rotating torque) , you should not simply loosen the pinion nut a little. You should disassemble the pinion and put a new crush sleeve between the 2 pinion bearings.
 
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vavaroutsos

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Pete, I believe they should be the same rotating torque whether installing new or used bearings, at the time of installation. I haven't specifically worked on a Dana, but other GM and Ford diffs. Diffs that have a crush sleeve between the 2 pinion bearings, will increase rotational torque only upon crushing the sleeve further. So, if you disassemble, or loosen the pinion nut, when you tighten it down again, it will have the same rotational torque as before, until you start to crush the sleeve further. That takes more torque on the nut than most people imagine. I would not use an impact to to that. You really want to feel the nut rotate. It's a fine line between not enough rotational torque and too much. We're talking very small amounts of rotating the nut with a long bar, then checking, repeat. If you go too far and the bearing has too much drag (rotating torque) , you should not simply loosen the pinion nut a little. You should disassemble the pinion and put a new crush sleeve between the 2 pinion bearings.
I only changed the yoke, I did not install a new crush sleeve or disassemble the differential. So either it wasn't setup properly from the factory, or the PTTR on oiled/broken in bearings is less than when new. You're right about how much torque it takes to crush the sleeve because the nut barely moved with a few hits of the impact on full power then pretty much stopped. I would have to keep the impact on it for more than a quick hit to get it any tighter. So I'm pretty sure it's back to where it was, and the PTTR indicates the same.
 

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Used bearings are always way less.

But did you yank axleshafts?
 

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Note on a "typical" D44 pinion bearing preload is 14-19 on new bearings and 6-9 for used.

Supposed to be much less on the "barnicle" bearings of the new axles.

On my Super60 front on my SuperDuty pinion bearing preload torque can be 5 in lb on used bearings....so it don't take much.....

Screenshot_20200531-151028.png
 

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vavaroutsos

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Used bearings are always way less.

But did you yank axleshafts?
No, I measured both before and after with axle shafts installed. Surprisingly (or maybe not), it doesn't seem to make that much difference. I tried adding some friction by rubbing my hand on the tire and it takes more force than expected to make much difference in PTTR. I guess due to the gear ratio, but I was surprised by the result as I though axle bearing drag would have had more of an effect.

I watched an install video on JLjournal and he measured 42 in-lb, but maybe his brakes were dragging or something. I guess I'll just have to keep an eye on things and listen for noise when decelerating. I'm going to re-gear soon anyhow.
 

roaniecowpony

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I only changed the yoke, I did not install a new crush sleeve or disassemble the differential. So either it wasn't setup properly from the factory, or the PTTR on oiled/broken in bearings is less than when new. You're right about how much torque it takes to crush the sleeve because the nut barely moved with a few hits of the impact on full power then pretty much stopped. I would have to keep the impact on it for more than a quick hit to get it any tighter. So I'm pretty sure it's back to where it was, and the PTTR indicates the same.
Sounds like you tightened up against the old crush sleeve, but didn't crush it further. The reason for the crush sleeve is to ensure adequate torque on the pinion nut to prevent backing off, while not driving the two bearings together beyond their design pre-load for good life and performance. If you have adequately tightened the pinion so it won't back off and the bearings are rotating within spec, you should be ok. It's not "the book" method, but many, many people get away with this. "the book" would have you replace the crush sleeve and pinion lock nut anytime you loosen the pinion nut.
 

roaniecowpony

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Note on a "typical" D44 pinion bearing preload is 14-19 on new bearings and 6-9 for used.

Supposed to be much less on the "barnicle" bearings of the new axles.

On my Super60 front on my SuperDuty pinion bearing preload torque can be 5 in lb on used bearings....so it don't take much.....

Screenshot_20200531-151028.png
Thanks, I have been corrected on the used bearing spec. ;)

On the measured rotational torque, my recollection was that this was without the ring gear on GM and Ford diffs. Is that the same for Dana's?
 
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vavaroutsos

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Sounds like you tightened up against the old crush sleeve, but didn't crush it further. The reason for the crush sleeve is to ensure adequate torque on the pinion nut to prevent backing off, while not driving the two bearings together beyond their design pre-load for good life and performance. If you have adequately tightened the pinion so it won't back off and the bearings are rotating within spec, you should be ok. It's not "the book" method, but many, many people get away with this. "the book" would have you replace the crush sleeve and pinion lock nut anytime you loosen the pinion nut.
Yeah, the idea was to tighten back down on the crush sleeve but not crush it further. The pinion nut is swagged from the factory to keep it from loosening. I also used some red loctite so I don't think it will come loose. The question in my mind was if the bearing pre-load was within spec. It seemed too low for a new setup and I didn't know how much it varied for broken in/oiled bearings.
 

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I personally wouldn't dream of anything resembling an accurate reading with the carrier in place, there's just too many variables....so:

1) F-it, run it!
2)tear it down and do it right
 

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vavaroutsos

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Thanks, I have been corrected on the used bearing spec. ;)

On the measured rotational torque, my recollection was that this was without the ring gear on GM and Ford diffs. Is that the same for Dana's?
Dana specs PTR (just pinion), and PTTR (with ring gear). PTTR is PTR plus some range depending on gear ratio. This is because the carrier bearing preload is constant and the gear ratio affects the drag added to pinion rotation.
 
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vavaroutsos

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I personally wouldn't dream of anything resembling an accurate reading with the carrier in place, there's just too many variables....so:

1) F-it, run it!
2)tear it down and do it right
I'm going with #1 until I do my re-gear. But this has me wondering if an impact wrench is going to be enough to crush a new sleeve. In the Dana video they have some jig to hold the yoke while they tighten the pinion nut. If an impact wrench won't do the job, I'm not sure how to hold the yoke without making some type of tool.
 

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A good impact like an IR2135 or M2767 will *probably* do it. You can buy yoke holders from Yukon or just make one (I choose the latter, they're simple)
 

roaniecowpony

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I don't like the idea of an impact on a pinion nut, with the bearings right there and with the carrier in place, you're banging on one place of the tiny contact patch of the gears. A yoke wrench and a big ass cheater to crush the sleeve has worked for me.
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