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Do You Really Need Grade 8, 9/16", Fine Thread, Partially Threaded Replacement Bolts?

Do You Really Need Grade 8, 9/16", Fine Thread, Partially Threaded Replacement Bolts?

If you have properly maintained your jeep and/or will continue to do so in the future, the answer is "no, you do not need them."

The stock, smaller-than-bracket-bolt-hole-and-bushing-sleeve bolts only become a problem when insufficiently torqued because the smaller size permits more violent oscillations within the bracket and bushings. This results in more violent oscillations commonly referred to as Death Wobble, and the extra play results in greater damage to brackets, bushings, welds, and other components.

Again, the undersized stock bolts are only a problem when they are not sufficiently torqued and maintained--the greater play when not sufficiently torqued is the common source of Death Wobble.

The bolts themselves are not a source of Death Wobble.


Now, many people who have done the swap have experienced improvement in tightness and handling of their front end and suspension. For some, they experienced Death Wobble before the swap, and it went away after the swap.

People who have experienced improvement from the swap to 9/16" Grade 8, partially threaded, fine thread bolts, had this experience because of the byproducts of the swap.

These byproducts may include one or more of:


  • the swap resulted in greater attention to torque and maintenance
  • the swap resulted in the owner purchasing a quality and calibrated torque wrench, learning how to properly use it, and becoming more familiar with how their jeep works
  • fine thread, partially threaded bolts stretch slightly less than the stock bolts, and as a result, they hold torque better (but this still does not negate the need for maintenance)
  • the swap resulted in pre-loaded/binding/twisted rubber bushings returning to a neutral position between the brackets at ride height (for people who did/had incorrect installs where bolts were not loosened for the installs)
  • for people who had not sufficiently maintained their jeep with stock bolts and bracket holes were egged out, the larger bolts helped center the bushing bolt sleeves over the holes for a more even clamping of that bushing bolt/crush sleeve force between the brackets
For people who properly maintain their jeep, don't have egged/wallowed bracket holes, and who don't have pre-loaded rubber bushings, the byproducts of the bolt swap don't really matter, and they do not experience any real difference from the swap.


But, what about using partially threaded bolts instead of fully threaded bolts in brackets and bolt sleeves?

Well, it doesn't matter if bushing bolt sleeves get scored by stock bolts. The scoring is only a concern if it is the result of looseness from lack of torque/clamping force. None of the joints or bushings corresponding to the bolts that are swapped are supposed to have the sleeves rotate on the axis of the bolts. The bolt sleees are to remain static between the brackets, and the suspension articulation is allowed by either the twisting of the rubber bushing, or the rotation of a joint.

The clamping force of 125 ft lbs of a stock bolt, with the bushing bolt sleeves set at a full and even contact surface on the inside of the bracket, is sufficient to prevent movement within the brackets.

If the contact surface inside the bracket is damaged, if the contact surface is uneven because the holes have been egged/ovaled out, etc., then the stock bolts may not be sufficient to center the bolt sleeve over the bracket holes.

A larger diameter bolt may be needed to center the bolt sleeve/bushing over the hole in order to get an even surface inside the bracket.

If the holes are severely egged out, the larger diameter bolt may be insufficient, and either washers or plate may need to be welded to the bracket to provide an even surface for the bolts, washers, and bushing bolt sleeves to hold the clamping force sufficient to prevent movement at 125 ft lbs.


Now, that being said, I still suggest that people consider doing the swap of at least the front trackbar bolts. Why? Because the cost is relatively small, and the byproducts can be helpful. But, it is more out of preference than a requirement.


Should you spend the equivalent of about 1/2 tank of gas and spend $40 to do a swap all of your front and your rear track bar bolts, and all of your lower control arm bolts?

Well, if you think that the byproducts of the swap are worth it, then go for it. Most of us waste $40 on things, recreation or entertainment of less value--on a regular basis.

Many of us change our engine oil more frequently than is needed and easily overspend $40+ more annually on oil and filters. So, what? It's a preference. It is a "conspiracy" by the oil companies and lube centers to tell us that we need to change our oil every 3k miles or 3 months instead of at the intervals recommended by the manufacturer in our owners manuals? Is it a "conspiracy" that some recommend synthetic oil? Maybe. Who cares? Some people with an axe to grind, maybe care. For the rest of us, it is a choice and a preference. Northridge4x4 and Synergy selling bolt kits is no conspiracy.


Now, swapping just the front trackbar bolts might cost you $6, plus or minus. They will hold torque better. The front trackbar bolts are the most critical with relation to steering and front end wobbles.


I wanted to post this thread to clarify my posts in my Diganosing Death Wobble threads.

In those threads, I wrote (emphasis added):

I'll start out by explaining that Chrysler decided to use a 14 mm trackbar bolt, with a trackbar bushing sleeve designed for a 9/16" bolt, and the trackbar bracket bolt holes are somewhere around 15-16 mm large. This is a sure recipe for DW if the trackbar bolts are not properly torqued and periodically re-torqued to 125 ft. lbs.

I swapped the trackbar bolts in our 3 JKs long before Northridge4x4 introduced their 9/16" bolt kit or before Synergy started selling volumes of their kit. Northridge4x4 sent me 3 full bolt kits to swap into our 3 JKs--at no charge. I've spent thousands upon thousands of dollars with Northridge4x4 and referred hoards of customers to them. I have recently discovered that there are a few unnamed bullies :9lame: on another forum :crazy: who actually are upset that Northridge4x4 sent me bolt kits for my 3 JKs (outfitted with purchases from Northridge4x4), and they are upset that Northridge4x4 referenced the video I had already made about swapping the front trackbar bolts. Really? Northridge4x4 threw in free bolt kits for people who purchased suspension kits from them for a long time after their introduction. Some people just need to grow up, "shut up and wheel," and stop acting like schoolyard bullies.:flipoff:



The smaller stock bolts are less of a design flaw than the failure of Chrysler to include torquing suspension bolts as part of a new car Pre-Delivery Inspection at the dealership, and to include torquing at least the front trackbar bolts at every oil change interval or two as part of normal maintenance.

Bolts stretch, metal fatigues, and suspension cycling/vibrations results in bolts losing torque. This is a bad combination with the 14 mm bolts in an up to 15+mm stock bracket hole and trackbar bushing bolt sleeve.

So, do you absolutely need to swap your bolts to 9/16"? No.

Should you to the swap? If you want the byproducts of the swap, and/or have some damage from egged/ovaled holes, then you probably should where the problem exists. If you want the peace of mind knowing that your front trackbar bolts will hold torque better and provide a snugger fit, then it is worth swapping the trackbar bolts.

Tech tip: Use a paint pen and draw a line across the bolt onto the mount for a visual.
 

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Thanks for the explanation. It should help a lot of people asking questions about lifts and aftermarket suspension work too.

:happyyes:
 

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Thanks for posting all this extremely valuable information. I had a '79 Bronco that I bought new that started to have DW issues and had to find the problem myself. There was not a front end shop in the country that knew any more than myself about DW at that time. All any of them wanted to do was throw parts at it without investigating for the true cause..
All the best to you and yours.
 

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Longest. Post. Ever. :D

These byproducts may include one or more of:

  • the swap resulted in greater attention to torque and maintenance
  • the swap resulted in the owner purchasing a quality and calibrated torque wrench, learning how to properly use it, and becoming more familiar with how their jeep works
  • fine thread, partially threaded bolts stretch slightly less than the stock bolts, and as a result, they hold torque better (but this still does not negate the need for maintenance)
  • the swap resulted in pre-loaded/binding/twisted rubber bushings returning to a neutral position between the brackets at ride height (for people who did/had incorrect installs where bolts were not loosened for the installs)
  • for people who had not sufficiently maintained their jeep with stock bolts and bracket holes were egged out, the larger bolts helped center the bushing bolt sleeves over the holes for a more even clamping of that bushing bolt/crush sleeve force between the brackets
Those right there are reason enough.
 

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Excellent info & explanation. Should be required reading. I'm a mechanical engineer that regularly deals with critical bolted connections, so I'm glad to see an in-depth explanation.
 

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I have the Northridge 4x4 bolt kit and plan on installing it this weekend. I also have the Mopar 3" lift... Is there anything I should be keeping an eye out for while I am swapping bolts? Any tips and tricks on the install?
 

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Discussion Starter #13
I have the Northridge 4x4 bolt kit and plan on installing it this weekend. I also have the Mopar 3" lift... Is there anything I should be keeping an eye out for while I am swapping bolts? Any tips and tricks on the install?
Don't torque control arm or trackbar bolts until the full weight of the vehicle is back on the springs at the new ride height.


If you are installing the lift at the same time:

You can use ratchet straps to pull the axle toward the frame or toward the front bumper.

You can have a helper cycle the steering right or left to help align the front trackbar bracket hole to the bushing hole. Attach the frame side first. Then use a helper to cycle the steering the to line up and attach the axle side.

You can use ratchet straps to center the rear trackbar bracket hole to the bushing hole.


If the lift is already installed, then just replace one bolt at a time (waiting to torque anything until they are all installed).

A helper can grab ahold of a tire and roll it forward or back to unbind/line up bracket holes, bushing holes, and bolts.

A helper can cycle the front steering to help with the front trackbar. They can push on the side of the rig for the rear trackbar.


It's a good idea to loosen the upper control arm bolts and vigorously rock the vehicle to unbind everything. Then, torque those bolts back to spec when you torque the new bolts.



Regardless, it is a good idea to use a small amount of antisieze on the threads if you live where they spread heavy salt or chemicals on the road in the winter.


You will want to retorque the bolts after about 50 miles driving. Then, do it again after every major wheeling trip and at every oil change interval.
 

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Regardless, it is a good idea to use a small amount of antisieze on the threads if you live where they spread heavy salt or chemicals on the road in the winter.
AFAIK, the torque specified is a 'dry' torque, meaning no oil, anti-seize or thread locker on the bolts. If you apply anti-seize you would need to torque the bolts to a lower value to achieve the same clamping force.
 

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I hate to throw a rock into the pond on this 14mm vs 9/16" issue, but I have some disagreement re: retaining the 14mm standard (fully threaded) bolts on lifted rigs. In my experience they may work ok on stock rigs with their limited wheel travel, but throw the increased wheel travel of a lifted rig at them with significant increases in wheel travel and the clevite bushings on control arms & track bars start to move, no matter what torque is applied. When they do, the threads of the 14mm standard bolts grind on the bushings, and the bracket holes. Using 9/16" shank bolts eliminates the excess clearance between the bracket & bushing holes and the bolt, and the shanks prevent abrasion of the bushings & brackets. On control arms with Johnny Joints on both ends there is less chance of damage to the bushing, but the bracket holes still can be egged out by the bolt threads when they shift under stress. With control arms using clevite joints at the frame, the need for the 9/16" shank bolts is more acute. Track bar brackets and bushings in particular benefit from the conversion to 9/16" shank bolts. Many cases of loose steering and death wobble have been traced to the 14mm standard bolts wallowing out the bracket & bushing holes, allowing the track bars to shift. These issues can arise even when the stock bolts are torqued to the specified 125ft lbs, and again it's simply due to the added stresses the additional wheel travel of lifted rigs exert on the bolts, brackets and bushings. Converting to 9/16" grade 8 shank bolts is an inexpensive upgrade that prevents this, it really does pay off.
 

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Thank you for the write up. This hits close to home for me since this weekend I discovered the bolt on my front trackbar (axle side) had not only loosed but drop the nut and was a few threads from FALLING OUT.

This is a 2014 JKU with 7k miles (and 2 wheeling trips) on it since putting in a 3.5" lift. I know the bolts were torqued on install. I agree you don't HAVE to do a replacement but I do feel people who wheel SHOULD do the replacement as well as check these bolts before / after every wheeling trip. Shame on me for being lazy. Lesson learned.
 

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When re-torquing is it best to just put the wrench on set at 125 lbs and see if it clicks or loosen and then re-tighten to the torque spec?
 

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Discussion Starter #20
When re-torquing is it best to just put the wrench on set at 125 lbs and see if it clicks or loosen and then re-tighten to the torque spec?
Just see if it clicks.
 
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