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Unread 05-11-2013, 07:13 PM   #1
mtnracer190
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Wj knuckle swap and unit bearing bolts

Im in the middle of a WJ knuckle swap. For those of you who have done it, which unit bearing mounting bolts did you use? Which are longer TJ,YJ,XJ,WJ? I know the size of the bolt so please I don't want to replace these with 6 point grade 8 bolts. I want to replace them with authentic mopar unit hub bolts.

Thanks,

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Unread 05-11-2013, 10:47 PM   #2
Bong_Holyeo
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I have been thinking about this exact thing because i am doing a WJ knuckle swap right now also. I included some pictures to illustrate what i am talking about.
The WJ bolts are longer than the YJ ones and they are the ones you want to use because of the .25" spacer you needed to center the U-joint with the ball joints. Now for what i am not sure of... if you examine the factory bolts they are wider in diameter by the head of the bolt on both WJ and YJ. I got a grade 5 bolt replacement bolt and works perfect but is the same diameter as the wider portion at the top of the factory bolts ... so why isnt the diameter of the factory bolt uniform all the way down when the replacement one that is works perfect?? i dont know? In the end i have the original WJ bolts but i think i will go with my grade 5 replacements in the end.
img_0522.jpg   img_0523.jpg  
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Unread 05-11-2013, 11:41 PM   #3
YJ4LIFE
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Quote:
Originally Posted by Bong_Holyeo View Post
I have been thinking about this exact thing because i am doing a WJ knuckle swap right now also. I included some pictures to illustrate what i am talking about.
The WJ bolts are longer than the YJ ones and they are the ones you want to use because of the .25" spacer you needed to center the U-joint with the ball joints. Now for what i am not sure of... if you examine the factory bolts they are wider in diameter by the head of the bolt on both WJ and YJ. I got a grade 5 bolt replacement bolt and works perfect but is the same diameter as the wider portion at the top of the factory bolts ... so why isnt the diameter of the factory bolt uniform all the way down when the replacement one that is works perfect?? i dont know? In the end i have the original WJ bolts but i think i will go with my grade 5 replacements in the end.
Why would u not get grade 8 or better? Chech out apr bolts they're 25% stronger than grade 8 and have some patents with rocketdyne that I use to work for. (rocketdyne made the space shuttle engines and apollo era engines for the moon)
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Unread 05-11-2013, 11:44 PM   #4
Bong_Holyeo
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only had grade 5 in the exact bolt with the correct thread length and all. any ideas on the reason why the bolt is wider on the head of the bolt? sorry did not mean to thread jack the op.
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Unread 05-12-2013, 12:25 AM   #5
YJ4LIFE
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Quote:
Originally Posted by Bong_Holyeo View Post
only had grade 5 in the exact bolt with the correct thread length and all. any ideas on the reason why the bolt is wider on the head of the bolt? sorry did not mean to thread jack the op.
Force through metal is like water flowing through a pipe. The wider head will spread out the force and carry more load. Www.mcmaster.com
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Unread 05-12-2013, 06:19 AM   #6
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I forget what the thread size was, I just know it was metric. I used some hex head grade 12.9 bolts and hardened washers when I did my swap. If you look at the heads, grade 12.9 is what the factory bolts are. I wouldn't substitute and less. You never know when you might hit a pothole and those weak grade 5 bolts decide to shear off.
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Unread 05-12-2013, 09:31 AM   #7
jbolty
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TJ and YJ bolts are identical; I carry a few as spares and have swapped them in both.

I would guess the stock bolts have a narrower shank to make assembly easier.

The shear strength of a 3/8 grade 8 bolt is about 10,000 lbs, a grade 5 is about 8,000. Hardly weak. A 12.9 metric is roughly the same as an SAE grade 9, but in any case almost any bolt you can grab off the shelf will be many multiples stronger than needed.

Keep in mind that Warn only provides 5/16 grade 5 bolts to mount their winches.
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Unread 05-12-2013, 01:44 PM   #8
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I have read threads where people were proud of using g 8 bolts to mount their seats.
Some people think that too much is just enough.
That said I would not use a lesser grade than the factory determined was required.

Dwayne
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Unread 05-12-2013, 07:02 PM   #9
mtnracer190
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Thank you bong Holyeo that was exactly what I was looking for. The factory YJ bolt is just a bit short for the spacer but it looks like the WJ bolt should fit perfectly. I'm going to stick with the factory flange head just like YJ4LIFE says the flange spreads out the force. I would imagine the extra contact surface of the flange head would help keep the bolt from backing off too. While grade 5 might be strong enough to hold up I wouldn't chance it with anything less than at least factory strength.

Quote:
Originally Posted by YJ4LIFE View Post
Force through metal is like water flowing through a pipe. The wider head will spread out the force and carry more load. Www.mcmaster.com
Thanks for all of the replies!
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