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Discussion Starter · #1 ·
I have a question about the pinion preload torque spec. I've been using a book written by Jefferson Bryant. He states the pinion preload on Chevy 12 bolt should be 14-19 in lbs. Yet it seems the consensus of those who are experienced on this site that it is 25 inch lbs. My final reading was 16 inch lbs. Should I be concerned & if so what are the consequences of it being 16 inch lbs.
 

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that spec is fine on used bearings. generally they recommend new bearings to be set at 25 inch lbs. make sure the races are seated.16 inch lb load is fine . i allways err on the light side .sneak up on the setting its easy to go to far. i have a 4 ft bar that bolts to the yoke that i use with a 3/4break over bar. makes it alot easier
 

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Discussion Starter · #4 ·
In response to Gary, the book i'm using as a reference says torque for use bearings is 6-8 inch lbs.,new 14-19 inch lbs. Since I have the entire rearend assembled I'm going to leave it at 16 inch lbs. If you or Freddie feel this is not acceptable then please let me know. Thank you for your input.
 

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Bill
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16 is good. The difference between 8 and 25 inch pounds is almost not measureable. It is more about getting everything seated and eliminating movement than smashing the bearing.
 

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If I was doing it I wouldn't be happy with 16. That would be fine for a 7.5 or 8.2 10 bolt with the smaller pinion bearings, but I wouldn't think it is enough for the larger bearings in the 12 bolt. This is just my opinion and totally up to you.

If you decide to go tighter then be very careful. It will only take a very small move of the pinion nut to gain the 3 to 5 inch pounds. Use a Sharpie and put a mark on the socket. Turn the nut just a little more than the width of the mark on the socket and that will probably get you right around 19 to 21. Even if you go as far as 25 it will still be good.
 

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new bearings are the key fact here. The preload is to keep the endplay tight once the bearings have seated to the races.
In 100 miles , the preload will be significantly less. If you put this much preload on used bearings , they will run hot , cooking the oil, and likely failure
 

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Discussion Starter · #8 ·
I used the Ratech solid spacer, so I would need to remove everything to change the pinion preload. These are new bearings not reusing the old. Ratech says to shim & torque to 125 ft lbs. Do you think by torqueing to 130 ft lbs it would increase the pinion preload higher?
 

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i would probably disassemble it and remove a few thousanths and recheck.. with the everything assembled you could check the total preload of the assy and then after you drive it 500 miles or so remove the drive shaft recheck and compare it to your 1st reading.you can tell by feel if its to loose .if i were you i would just tighten it up a little and be done. to be honest as long as it has some load on it you would probably never know the difference
 

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If you decide to go tighter then be very careful. It will only take a very small move of the pinion nut to gain the 3 to 5 inch pounds. Use a Sharpie and put a mark on the socket. Turn the nut just a little more than the width of the mark on the socket and that will probably get you right around 19 to 21. Even if you go as far as 25 it will still be good.
Good advice! That preload gains QUICK once you are in the neighborhood......
 

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If you used a solid spacer then removing .001 inch would probably put you in the right range. Increasing the torque on the nut 5 foot pounds won't make a difference, but increasing it about 50 would. I usually go between 150 and 200 foot pounds on a solid spacer. Sometimes changing the shim .001 is too much of a change in preload, so I make small adjustments by changing the torque on the nut.
 

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Discussion Starter · #12 ·
Freddie, can that torque increase be accomplished with the rear assembled as is, or do I need to disassemble to make the torque increase?
 
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