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Answers To All Your Jeep Questions

Posted in How To: Tech Qa on May 2, 2018
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Over Focus T-Case

I have a tech question about transfer cases that I hope you can help me out with. I have a ’05 Wrangler TJ Unlimited with a 4.0L, NSG370 manual transmission, and an NV231 transfer case. I am in need of either a slip-yoke eliminator kit, or better yet, I would prefer to put in a transfer case with a 4:1 low-range gear. The obvious first choice would be an NV241 Rock-Trac transfer case from a Jeep Rubicon. It would bolt right up and be much cheaper than any of the aftermarket transfer cases. The main problem is that they are hard to come by in my area. It is much easier to find an NV241 out of a JK. The JK doesn’t have the same output shaft speed sensor setup that I require for my speedometer. I daily drive my Jeep and the speedometer is a must-have.

Do you know of a way to make the factory TJ speedometer work with a JK transfer case? Is it possible to swap out the output shaft and bearing retainer on the JK case to a TJ style? Do you know of any companies making a kit for this? Are there any other options I am not aware of? Any suggestions to make a JK case work would be appreciated.

Lorne Baxter
Via email

As you have found, the ’07-’18 JK NV241OR Rock-Trac transfer case does not have a speedometer sensor and tone ring on the rear output. The JK gets its speed reading from the wheel sensors, which also control the ABS, traction control, and stability control. In order to use the JK NV241OR, you’ll have to add a three-wire square wave speed sensor and tone ring. The easiest low-buck way to do this would be to fabricate and attach a tone ring to the rear output yoke, then build a bracket that attaches to the back of the transfer case to hold the speed sensor. It’s a relatively cheap solution. However, the tone ring and sensor could get fouled or damaged by mud and other trail debris.

Realistically, I think your best solution is to look outside of your immediate area for the proper TJ NV241OR Rubicon transfer case, which will bolt up to your Jeep transmission and give you the speedometer output that you need. A quick search online revealed several TJ Rubicon NV241OR transfer cases on eBay (ebay.com). They typically run $2,000-$3,000 without a core.

Hi-Low Steering Swap

I am preparing to do a high-steering revision and a track bar relocation to my ’01 TJ. It has a Ford Super Duty Dana 60 front axle. Is there any reason or benefit to mounting the steering linkage to the top or bottom of the arm at the knuckle? Thanks for any insight.

Bob Crooker
Via email

Generally, the reason for installing high-steering arms on an axle is to get the steering linkages up and out of harm’s way. With this logic in mind, you’ll want them to be as high up as possible. So you’ll usually want to attach the linkages to the top sides of the steering arms. However, when installing high-steering arms on any axle, it’s important to check for clearance, especially on Jeeps with low center of gravity suspensions. It’s not uncommon for the tie rod or drag link to bump into the frame, steering box, or other chassis component. You may need to cycle the suspension to properly check the clearance. While doing this, you can mock up the drag link and tie rod into both locations to see what fits and what doesn’t. Don’t forget to cycle the steering back and forth as well as cycle the suspension through all different scenarios. This can be achieved by safely supporting the chassis of the Jeep, removing the coil springs, and articulating the axle with a pair of floor jacks.

Shafting Experience

I got to wondering if you people at Jp ever ran an article on trail repairs for broken axles, differentials, and so on. I never saw it if you did, so humor me. I have a ’14 JK Rubicon Unlimited with 35-inch Goodyear MT/R tires, a 4-inch Mopar lift, and a lot of junk that I haul around, which includes tools, recovery gear, jack, and so on. The suspension sits about 3/4-inch off of the bumpstops, so I guess it’s loaded heavy.

Anyway, if I break an axleshaft, will the tire and wheel just come off and roll down the trail? Is this Rubicon Dana 44 a semi-float axle? If the axleshaft breaks, but the wheel will stay on, is it OK to limp off of the trail, and if so should I keep it shifted in 4x4? Should I lock the differential on the broken axle? For some reason I assume it will be a rear axleshaft that breaks. Would it be better to yank the rear driveshaft and motor out in front-wheel drive or vice-versa if it was the front axle that broke?

If I carry a spare axleshaft, assuming the rear shafts are the same length, would the bearings have to be pressed on already? Exactly how would you go about this on the trail? If this is doable, how do you get the broken splined stub of the axle out of the differential? If I blow up my brand-new G2 5.13 gears, will it wreak havoc if I try to get off the trail with the other differential, and would you pull the driveshaft at this point?

I realize I went over my quota of questions, but I don't seem to understand everything I should know about this stuff. I’m going to Moab soon, so I figure I will be better prepared if anything exciting happens to my rearend.

Bruce Williams
Corrales, NM

That’s quite the myriad of driveline trail repair questions. Unfortunately, there isn’t always a simple answer to each question. There are many variables and sometimes other obstacles that will need to be overcome. For simplicity’s sake, we’ll stick with the JK axles, because some other popular axles would require a slightly different thought process.

If you break a rear axleshaft, it will generally break where the splines end. This is usually the narrowest and weakest area. Although, an axleshaft could fail anywhere along its length. Your JK rear axle is a semi-floating rear axle. The axle bearing is pressed onto the axleshaft and a retainer plate keeps the axleshaft and bearing in the axlehousing. If the axleshaft does fail at the splines, or anywhere between the axleshaft bearing and the splines, the bearing retainer and brake caliper will keep the wheel and tire assembly on the axlehousing. It will be wobbly and unstable, but it should roll well enough to get your Jeep off of the trail and onto a tow truck. Now, if for some reason the rear axleshaft fails on the outside of the bearing, the wheel will typically break free from the grasp of the brake caliper and exit the wheelwell. This type of axleshaft failure usually only happens in really abusive conditions.

The right and left rear axleshafts in the ’07-’18 JK are different lengths. The right shaft is 32 5/8 inches, and the left shaft is 31 1/4 inches. They are not interchangeable, so if you want to carry spares, you’ll need both sides. Companies such as Mopar (mopar.com), Spicer (spicerparts.com), and Yukon (yukongear.com) offer factory replacement axleshafts assembled complete with the axle bearing, seal, retainer, and ABS tone ring.

If you are concerned about the strength of the stock axleshafts under your loaded-down Jeep, you could replace them with heavy-duty 35-spline parts from companies like Dynatrac (dynatrac.com), G2 (g2axle.com), and RCV (rcvperformance.com).

Limping a Jeep with a damaged axle usually requires some assessment and repairs prior to getting underway. You should be able to figure out exactly what is broken and know if it’s binding in any way. Binding can cause a lot more damage, so it’s best to free up whatever is stuck instead of abusing the parts further. Locking the rear locker with a broken rear axleshaft with help get your Jeep off the trail more easily. Needless to say, you will want to baby it off the trail.

A broken ring-and-pinion could have the busted teeth jammed into other areas of the axle. Ring-and-pinion failure usually requires that you pull the differential cover and remove the broken bits. Loose gear teeth in the axle assembly will cause it to unexpectedly and randomly lock up. Not even removing the driveshaft can guarantee this won’t happen. If the rear ring and pinion are completely shot, you can remove the rear driveshaft after clearing the broken bits out of the housing. In some extreme cases you may need to remove the ring gear and reinstall the empty carrier in the axlehousing.

Removing the splined section of a broken axleshaft from the carrier is tricky business. Sometimes you can pull it out with a powerful magnetic telescoping retriever tool; sometimes you can tap it out with a rod from the other side; and sometimes you have to remove the carrier from the axlehousing before pounding it out. It’s usually not at all a fun job in the dirt.

Like the rear axleshafts, broken front axleshafts require similar evaluation prior to limping out. They typically fail at the steering U-joint. If you hear popping up front, it’s important to let off the throttle immediately. A broken steering joint can lead to the axleshaft ears trying to pass each other if you stay in the throttle. This can cause the ball joints to pull apart and the entire steering knuckle and wheel to free itself from the axle assembly. The broken axleshaft ears can also keep the steering from functioning properly. Front axleshafts with a broken U-joint or ears should be removed or replaced before limping off the trail. If a splined end of a front axleshaft breaks, it’s not as big of a deal, although you should disassemble the axle and remove the broken bits before continuing on. A broken front axleshaft can flop around inside the housing, bind up, or potentially cause damage to the inner axle seal and seal mounting surface. The JK unit bearing does not require the stub shaft to be installed like some other unit bearings, so you can completely remove the offending axleshaft, stuff a rag in the axletube to keep the oil in, and limp off the trail in three-wheel drive. You can use the front locker in this scenario, but you should baby it.

Ideally, you can avoid all of these axle failures. Driving sanely and matching the tire size and load capacity to your axles is the best way to avoid this kind of destruction. You may want to consider carrying less equipment, especially if you don’t need it for every trip. The 35-inch tires are about the maximum tire diameter I would recommend for the factory Dana 44 axle assemblies.

Fuel Pick-Me-Up

You gave me some brake advice a while back that was spot on. Thanks so much for helping me overcome problems with my build. I have a new problem. I need to extend the fuel pickup for my ’67 CJ-5. I got a plastic underseat fuel tank and it’s taller than the steel one. I’d like to add a flexible tube with a strainer on the bottom so the engine won’t starve for fuel when at odd angles. I’d prefer to use something I can just clamp onto my existing pickup tube. Any and all advice is welcomed.

Chuck Merritt
Via facebook.com/JohnCappa4x4

Early Jeeps with the flat and shallow underseat fuel tanks have always been a challenge to keep fueled at odd angles, especially when the fuel level gets low. If you have access to the inside of the tank via the sending unit hole or you can pull the feed line out, you should be able to simply splice in a longer feed. All it takes is some fuel hose, a steel tube, and a couple of hose clamps. If you are concerned about the pickup sucking air and not fuel at the least opportune time, consider adding a Holley (holley.com) HydraMat to your fuel tank. The HydraMat is a fuel reservoir system designed to reduce fuel starvation issues during hard cornering, acceleration, stopping, inclines, and low-fuel conditions. There are many different sizes available that can be plumbed into nearly any fuel tank.

Crawl Ratio Calculations

I need a sanity check on my calculations. Simply stated, I want my CJ-2A to have a crawl ratio near 220:1. I’m limited by the available parts, but I think I can do it with an SM465 manual transmission and an NP203 doubled up to a Dana 300 transfer case stuffed with a 4:1 gear set. Advance Adapters offers the NP203 to Dana 300 adapter and I have the SM465 to NP203 adapter. Even with the doubler adapter and 4:1 Dana 300 gear set, this is still the least expensive option. I have also considered using the elusive SM420 transmission, but they are hard to find. Up here we have tons of SM465 transmissions but very few SM420s. If you do find one, they are usually very far away, expensive, and scary to purchase sight unseen. When I found my SM465 it was factory-mated to an NP203. It has been suggested as being available in 1972, so I guess I won the lottery!

The Jeep will have a 4.3L V-6 from a ’02 Chevy S10 and roll on 285/75R16 or similar tires. I plan on using the Jeep to crawl over rocks, ford through water, and dip into the occasional mud bog. I may also be pulling a small camp trailer. Aside from the challenge, I prefer crawling or winching up and over things. I will be wheeling in northern Quebec and Ontario, Canada. I think of it as an expedition vehicle that can make 120-mile round tips to my favorite fishing hole. I also need to carry or pull enough gear for up to 10 days. I normally take these trips solo.

Jeffer Bear
Via facebook.com/JohnCappa4x4

Stuffing a 4.3L V-6 mated to an SM420 or SM465 into a flatfender is no small feat, and mating it to an NP203 doubled up to a Dana 300 is impossible. If you try to retain the factory body and wheelbase, your rear driveshaft would likely be in the neighborhood of 2-3 inches long, which obviously isn’t at all workable. You would have to extend the body or lengthen the wheelbase at the rear axle at least 10-12 inches or more to make a drivetrain combo like this a viable option.

The SM420 transmission is getting harder to find. Parts are difficult to locate too. The last one came off of the assembly line in the late ’60s, so the newest one you will find is still more than a half-century old. The SM465 that you have can be made to work, but it is very large. If you decide to go with an SM420, Herm the Overdrive Guy (hermtheoverdriveguy.com) offers rebuilt transmissions with or without an adapter.

Installing a doubler in front of a Dana 300 is a bit of a gamble on heavy or high-powered Jeeps. While the Dana 300 is incredibly robust for its size, it still only has a smallish 23-spline input and 26-spline output shafts. The rear output is often considered to be the fusible link of the Dana 300. The good news is that there are heavy-duty output shafts available for the Dana 300. Companies such as Advance Adapters (advanceadapters.com), JB Conversions (jbconversions.com), and Novak (novak-adapt.com) all offer heavy-duty, 32-spline Dana 300 rear output conversion kits. JB Conversions also offers a 32-spline front output conversion.

Given your vehicle choice, powerplant, tire size, and intended use, I think the 220:1 crawl ratio is overkill. While I can appreciate the gearing versatility of having a 2:1 low-range ratio doubler in front of a 4:1 low-geared transfer case, I don’t think you will ever find a situation where you will need the compounded low gearing, or for that matter the 4:1 geared transfer case all by itself. I have a 93:1 crawl ratio on a similar Jeep with the same 4.3L V-6 engine and 33-inch tires. I rarely use low range and First gear except in extreme rocky technical terrain with large boulders. I think you’ll really like the stock 2.6:1 low range in the compact Dana 300 when coupled to a four-speed truck transmission like the SM420. With 4.56 axle gears, this combo would put you at an 83:1 crawl ratio, which is more than enough for almost everything you could encounter. If you planned on Johnson Valley heavy rock work you would likely want to error a little closer to 100:1, but for what you are doing it should be a better match and more versatile than the doubler setup or 4:1 geared transfer case.

Laid Back

What are the reasons or benefits of leaning coilovers at an angle in certain applications?

@realjeepsarefullsize
Via Instagram @cappaworks

Custom-fabricated suspension conversions come in all forms. Coilover shocks have become a popular, versatile, and compact package that provides weight carrying capacity and suspension damping. Coilovers are easier to mount than most spring and shock suspension designs, especially when space is at a premium. They also offer near infinite adjustability for spring rates and shock valving.

In most cases, coilovers are mounted to the axle and in line with suspension movement. However, there are situations where this is not always possible or desired. Mounting the coilovers at an angle can help fit a longer shock into a smaller area or help keep it clear of other components that may make contact as the suspension cycles, such as the tire, frame, and so on. Some people inaccurately believe that tilting the shock at a slight angle will significantly alter the motion ratio of the shock and the effectiveness of the shock valving. This could not be further from the truth when dealing with the 1:1 movement of a solid 4x4 front or rear axle. The motion ratio of a shock bolted directly to a solid axle is only minimally altered when the shock is angled. For example, on a typical link suspension with a coilover mounted vertically on the axle, the coilover will compress 1 inch for every 1 inch of suspension travel, providing a 1:1 shock motion ratio. When you angle the coilover to even an extreme and unheard of 30 degrees on the same suspension system, the result is a motion ratio of 1:0.866, meaning the coilover shock travels 0.866 inches (or about 7/8-inch) for every 1 inch of suspension movement. Tilting the shock to a more reasonable 15 degrees results in a motion ratio of 1:0.966. Neither of these scenarios would require special shock tuning above and beyond a 1:1 motion ratio application. By comparison, a performance A-arm suspension might have a shock motion ratio as high as 2:1, where the shock only travels 1-inch for every 2 inches of actual suspension travel. In this situation, the shock valving would need to be changed to compensate for the motion ratio. Motion ratio and other important coilover calculation data can be found on the Hyperco (hypercoils.com) website.

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