We'd come to love our Wrangler YJ. It had proven itself a likable and competent friend for family outings in the Adirondacks. Even my wife was beginning to understand this four-wheeling thing, having ignored my warning and burying the Jeep on the road to Otter Creek. She called me at camp for help, and I had to negotiate the trail in her mother's four-door Blazer to extricate the YJ. Heck, even her mother thought the whole thing was cool. It was with sentimental tears that I decided to sell the YJ to help fund the purchase of a TJ.
I had come across a half-completed TJ V-8 conversion project that needed a new home and seemed the perfect rig for our adventures. It ran and was driveable, but needed much buttoning up to be trailworthy. After all, this was someone else's idea, started with great gusto, but the job was far from finished. No transfer-case linkage, no gauges, leaking a little here and there. Almost done, no big deal, right? Well, you know how it goes.
Once I had the TJ in the garage and took a close look, it became obvious I'd need to take a few steps back. Good intentions are not enough when you're talking safety, reliability, and money. The previous owner had put together the right parts: low-mileage TJ, small-block Chevy, TH400 tranny, Advance Adapters transfer case/transmission mount, engine mount, and headers. The problem was that all the parts had been assembled using questionable hardware and assembly methods in an otherwise stout drivetrain arrangement. So out came all the fasteners from the motor mount to the driveshafts. Every nut and bolt was scrutinized and replaced with the correct size and grade, then reassembled with a liberal dose of Loctite.
The nut-and-bolt combination has two main functions: to provide a clamping force, and the ability to remove that force when required. The clamping force is generated through tension in the bolt, which occurs as the bolt stretches during the tightening process. Removing the force requires breaking the friction between the threads and allowing the nut to unscrew.
The amount of available clamping force is determined by the grade of fastener and how far it will stretch before losing elasticity. Generally speaking, Grade 5 is adequate for automotive applications. Sometimes, Grade 8 is used. Grade 2, typical of hardware-store bolt bins, is questionable for structural assemblies. Matching the material and size of the flat washer to the nut and bolt is very important. The key to a reliable bolted joint is generating adequate clamping force and then locking the nut in place to maintain tension in the bolt.
The chart on page 66 displays the SAE torque values of the most popular grades and sizes, which should help you decide what you need for any application. There are differences in torque values for bolts based on materials (high-carbon, copper, zinc, and so on) and construction (heat-treated, quench-tempered, case-hardened, and so on), so use this chart only as a ballpark estimate. Remember, too, that stronger is not always better, as some bolts are intentionally designed to fail before extreme torsional stresses can be transferred to other (more expensive) components.
Welding, bonding, or use of a rivet is a way of unitizing parts and preventing unwanted disassembly, without the benefit of easy removal. A liquid threadlocker unitizes the nut-and-bolt assembly by filling the air space between the threads with a chemical resistant plastic.
Vibration and thermal cycling can cause a threaded fastener to come loose with sometimes devastating results. There are many mechanical devices designed to keep a nut or bolt from coming apart. Some work, some don't. The split-ring lock washer is not very effective. Nylon insert nuts have been known to loosen just enough to reduce effective clamp force. The easiest way to ensure the nut stays put is through the use of a liquid chemical threadlocker such as Loctite.
The benefits of using a liquid threadlocker include preventing rust and corrosion and easy removal in the future through the use of force or heat. We've all been there before, fighting with that rusted or heat-seized nut or stud that refuses to come loose. Along with busted knuckles, the scene generally degrades to Vise-Grips, drilling, cutting, or torching. Threadlocker will minimize the aggravation factor.
Liquid threadlockers are anaerobic adhesives used on metal fasteners. The liquid cures to solid plastic in the absence of air. If you leave a puddle of threadlocker exposed to the air it will never harden. If you remove all the air, such as between two parts, the liquid will solidify. The presence of active metal such as copper or steel will speed the cure, while inactive metals such as stainless steel or cadmium plating cure slowly and may need to be primed. Loctite 7649 Primer N is a copper-filled spray that is applied to inactive surfaces to ensure cure, speed the cure, and cure to greater depths.
Threadlockers are formulated for different removal strengths: 222, or purple, is low strength designed for use on small fasteners that allow disassembly with a screwdriver; 242, 243, and 248 are blue, medium strength and can be removed with handtools; 262, 271, and 268 are red and considered permanent, designed to withstand tremendous removal forces; 220 low strength and 290 medium strength are wicking types designed for post-assembly application; and 272 is a high-temperature permanent version that withstands temperatures up to 450 degrees. By comparison, most other grades of threadlockers withstand temperatures of 300 degrees.
OEM's have used threadlockers for years. They are dependable, provide predictable removal, and are easy to use. Understanding the properties of your fastener is the first step in achieving maximum performance. Utilizing a liquid threadlocker takes it to the next level through maximum reliability. In most instances, these gas-, oil-, and chemical-resistant threadlockers are well worth the few cents it costs per application.
|Bolt size (in.)||Grade 2*||Grade 5*||Grade 8*|
|11/44 - 20||6||10||14|
|51/416 - 18||12||19||29|
|31/48 - 16||20||33||47|
|71/416 - 14||32||54||78|
|11/42 - 13||47||78||119|
|91/416 - 12||69||114||169|
|51/48 - 11||96||154||230|
|31/44 - 10||155||257||380|
|71/48 - 9||206||382||600|
|1 - 8||310||587||880|
|111/48 - 7||480||794||1,430|
|111/44 - 7||675||1,105||1,975|
|131/48 - 6||900||1,500||2,650|
|111/42 - 6||1,100||1,775||3,200|
|151/48 - 511/42||1,470||2,425||4,400|
|131/44 - 5||1,900||3,150||5,650|
|171/48 - 5||2,360||4,200||7,600|
|2 - 411/42||2,750||4,550||8,200|
Coarse thread per inch
*Minimum tensile strength
Grade 2= 74,000 psi, Grade 5= 120,000 psi, Grade 8= 150,000 psi
|220||Low strength||Purple||Liquid||Wicking grade for small pre-assembled fasteners|
|222||Low strength||Purple||Liquid||For fasteners under 11/44 inch|
|242||Removable||Blue||Liquid||General purpose, easy removal|
|243||Removable||Blue||Liquid||Oily fasteners, cures faster, remove with handtools|
|248||Removable||Blue||Stick||Paste, won't run or drip, remove with handtools|
|262||Permanent||Red||Liquid||Fasteners under 31/44 inch, remove with heat|
|271||Permanent||Red||Liquid||Fasteners over 31/44 inch, remove with heat|
|268||Permanent||Red||Stick||Paste, remove with heat|
|272||Permanent||Red||Liquid||Withstands 450 F, remove with heat|
|290||High strength||Green||Liquid||Wicking grade, may require heat to remove, seals welds|
|7649||Primer||Lt. Gn.||Spray||For inactive surfaces, speed the cure, cure deep gaps, 30-day on part life|