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September 2013 Your Jeep

Posted in How To on August 8, 2013
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Photographers: JP Staff

We Feel Your Pain
I have a ’79 J10 with a 360 engine, T-18 tranny, and a Dana 20 T-case. Recently, my work transferred me to another plant 15 miles away. The J10 is my daily driver. I was wondering if anyone here has done or has a link to an article about swapping in a five-speed tranny. I just want to lower my rpms while doing 65 mph. Hopefully this will improve fuel economy as well.

Yep, that sounds familiar. Our ’78 J10, Piggy, has the same drivetrain and came from the factory with 4.10 axle gears. Somehow someone was patient enough to put about 85,000 miles on it with stock-size tires. That’s a lot of high rpms from a V-8 that does not like to rev or some really slow highway driving. Now we have lifted Piggy and are running some 36-inch tires, so you’d think it would be a highway cruiser, but it still approaches 2,700-3,000 rpm on the highway. Well, like us, you have a few options. One option you could pursue is to track down an NV4500 from a ’93-’94 Chevy truck. There are other transmissions with an Overdrive, but they lack the granny First gear that your T-18 has. An NV4500 is not gonna be the cheapest or easiest option, but it is an option. Another way to lower highway rpms is to switch to higher (numerically) axle gears or go to larger diameter tires. Unfortunately the AMC V-8s don’t seem to be at all efficient. They are the heavy drinkers of the V-8 world. On top of that, the factory did not skimp on the steel when building our trucks. The sheetmetal, when not rusted away, is thick and heavy. Some people will advise an entire drivetrain swap like a diesel and a tranny with an overdrive. How ‘bout a more-modern V-8 and an auto tranny with an overdrive? That has given many FSJ owners a mileage increase. Having said that, the cost of any of these conversions probably won’t ever pay for themselves with fuel savings. That does not mean you should not do it, it just means your FSJ and mine can’t easily or cheaply get decent gas mileage. Another option, and again, it’s not gonna be cheap or easy, is to try to track down a rare Borg Warner/Rancho Overdrive for a Dana 20. They are heavy, only work in 2WD, and are very rare, but they do exist, and if you can get one that works or can be fixed, you can bolt it to your J10, have a shorter rear driveshaft built, and drop the rpms on the highway. One last option would be to swap to an NV3550. You’d lose the granny gear, but you’d pick up an Overdrive.

The Pressure Is Killing Him
I own an ’87 jeep YJ with the 4.2L engine, and I keep having trouble with my oil pressure. I’ve already replaced the oil sending unit twice, and the pressure on the gauge keeps dropping. Could this be the oil pump going out on it, or could it be another PCV valve, or what? I’m stumped and have no idea. I do know for a fact that it is a mechanical gauge, but should the pressure really read the line before zero at interstate speed?
Derrick Knight
Plant City, FL

Hmm. It sounds like you may need a new oil pump. But to check the first thing, I’d toss a new PCV valve at it (cause that ain’t gonna hurt) and hook up a mechanical aftermarket oil pressure gauge. That is a new one with a capillary tube. If your current gauge has a sending unit that is replaceable, then it is probably not truly a mechanical gauge. A true mechanical gauge will tell you if your gauge is malfunctioning or if you need a new oil pump. Sure, you’ll have to buy a gauge that may tell you what you already know, but it’s easier than tossing a new oil pump in the Jeep first thing, and heck, who doesn’t want a nice aftermarket oil pressure gauge?

Right From the Horse’s Mouth
I have a question about a project you guys did a while back. You guys did a 5.9L Magnum swap on a Jeep TJ (“More Mopar,” Parts 1 and 2, July ’11 and Aug. ’11). I am doing the swap as well, and with California’s smog stuff I have to run a mechanical fan. With that said, have you guys had any cooling problems? I will be blasting the A/C in 115 degree heat in the California summer in the desert. Please let me know how it is going! Everyone online has gone with electric fans, and that will not work for me!
Mike Zeko
Brea, CA

To answer your question we went right to the source and talked to Ali Mansour, Four Wheeler magazine Technical Editor, who wrote the articles covering the V-8 conversion in his very own TJ. Here is what he said: “The TJ does not have A/C, but does in fact still run the mechanical fan (which I prefer over electric). I have never had any heating issues, even in weather over 100 degrees. I don’t have much of an inner fenderwell, which helps dissipate some of the heat. Prior to swapping in the engine, I removed all of the core plugs and cleaned out the water jackets (it was pretty gunk-filled). I also put in a new thermostat and water pump to be on the safe side. To date, I never have heating issues, but I wouldn’t mind putting back the A/C one day!”

Attack of the Flasher
I don’t know if this is the right section or not, but I was trying to contact Randy’s Electrical. I have been a subscriber for a few years now and finally ran across a question I could ask him. I have a ’98 TJ, and recently changed the taillights out for some flush-mount LED oval-shaped trailer lights. I have them wired up and everything is working. My question is, when I turn the turn signals on, it flashes fast as if the bulbs are blown, but none of them are blown. Is there a diode or anything I can put in line to stop the fast flashing?
Benjamin Tugwell
Lucama, NC

Yep, that will happen with a Jeep with an older style flasher installed. There are a couple ways to deal with this, but the easiest is just to go down to the parts store and get a new flasher that has provisions for LED lights. One that will work is the Trico EP-26 flasher with the “LED” notation on it. Then when you get home, stick your head under the dash, pull the old flasher, and install the new one.

More Mysterious Clunks
I have installed an ’01 Super Duty Dana 60 front and Sterling 10.5-inch rear in my ’01 TJ. After much reading on the subject, I decided on Detroit Lockers for both. They were installed by a national 4x4 company. There are the occasional clunks that I expected, but overall I’m happy very with the lockers. The only noise that I can’t seem to verify as “normal” from any source is a regular knocking from the rear when coasting that is about in time with the tire rotation. I expected and accept noises, but haven’t been able to find out if this one is normal. Thanks for any input.
Via email

Well, clunks and drivetrain noise are probably one of the hardest things to diagnose without getting some seat time in a moving vehicle. On top of this, Detroits, while being brick-shithouse-solid and reliable, are also noisy. Having said that, your description of the noise being in time with the tire rotation probably means it’s coming from a wheel bearing or carrier bearing. Any pinion bearing noises will be faster than tire rotation because the pinion is before the reduction from the ring-and-pinion. You could try jacking the axle that you think is making the noise off the ground, put the Jeep in Neutral, and rotate the tires by hand to see if you can hear the noise. This will also help verify if the noise is in time with tire rotation or not. A carrier bearing could have been damaged during installation, or just from mileage and age if you reused the wheel bearings in these axles (you should have bought new carrier bearings for the differential install). If you can’t figure out what is causing the noise and the place that installed the Detroits is not worried about it, there is not much you can do but drive it. If there is a problem, it will develop into something that the 4x4 shop that did the work will be able to identify. Hopefully they will stand behind their work. Just make sure they know that you think something is off and that you contacted them about it after the modification and they gave you the all-clear. Let’s hope they have some warranty on their work that they will stand behind.

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Oh Boy!
I have a ’79 CJ-7 six-cylinder that had all of the emissions pump and related equipment removed and a header installed. I moved from Iowa to Colorado, and now the vehicle has to comply with Colorado emission laws, which means it fails without the original emission equipment. The body is rough. I was thinking about replacing the tub, but now have to round up all of the missing equipment, which adds additional cost. My question to you is would I be better off to sell the old Jeep and buy something like a TJ with all of the original emissions equipment, or is the old CJ-7 drivetrain and suspension superior to the newer TJ?
Alan Bauler
Via email

Oh boy, I should know better than to comment on this, as I am sure I will just enrage all the CJ-7 fans out there. The truth of the matter is that a stock later-model TJ is a way better vehicle than a stock CJ from the ’70s or ’80s. I will say that the looks of a CJ-7 are arguably better than a TJ, and certainly better than a YJ with its square headlights, but there is plenty of sound reasoning for feeling a TJ is superior in many ways to a CJ-7 when stock vehicles are compared head-to-head.

The frame of the TJ is much better. It’s fully boxed on a TJ while a CJ-7 has a 2 C-channels welded together. The CJ-7s are well known for developing stress cracks around the steering box. Now that’s not to say you can’t break a TJ frame, or that with time and use a TJ frame won’t develop stress cracks, but in a straight-up comparison a TJ frame is stronger.

Now, on to other parts of these Jeeps. If you wonder if a TJ’s suspension is superior to a CJ-7s then I can tell you have never ridden in a TJ. The hands-down easy winner in suspension design is the TJ. They ride better on-road and work better off-road with their multi-link suspension and coil springs. Riding on a bumpy road in a CJ-7 is a tooth-rattling butt-aching proposition. The same road in a TJ, well, it’s so smooth you should probably slow down to avoid bending the axles. As for the rest of the Jeep, the easy nod goes to the TJ’s 4.0L HO. This is a super-reliable engine that makes power and gets pretty decent gas mileage. The induction is far superior to that of the CJ-7’s 258 I-6. Also, I’ll say a stock 4.0L HO is better than a stock emissions-strangled AMC V-8 found powering a CJ-7.

As for four-cylinders, both the CJ’s four-banger and the TJ’s are dogs, but the TJ’s micro mill has a reliable multiport injection while the CJ’s four-cylinders breathe through a problematic Carter carburetor. As for axles, both Jeeps are in need of upgrades if you use them off-road and or plan on large lift and big tires. I like the TJ’s Dana 30 front axle. As long as you don’t jump the Jeep much they will last for years and the slightly larger U-joints mean they are just a little stronger than the CJ’s Dana 30 front axle. As for the rear axle the TJ’s Dana 35 is a turd and should be avoided. The AMC-20 that the CJ-7 will have is a way better axle…that still has problems. Next on the hill of rear axle quality is the optional TJ Dana 44. This is a pretty good axle, but the housings are not that strong because of thin-walled axletubes. The king of the rear axle hill is the ’86 CJ-7 Dana 44. With flanged axleshafts, thicker axle tubes the CJs Dana 44 is a great axle…that was only available in the last year of CJ-7s. Now as for T-cases, the CJ-7 Dana 300 is a stout part, but that’s not to say that the NP231 or NP241 in a TJ are not great T-cases. Both are more than adequate for most Jeepers. We can keep comparing major systems of these two Jeeps and talk back and forth about the benefits of overdrive transmissions, galvanized sheet metal, locking hubs or lack thereof debating what’s best. The fact is that a TJ is a great Jeep with many modern improvements over the CJ-7. Also, every TJ you see is at least 10 years younger than any CJ-7 you’ll come across. Both have loyal groups of owners, and these groups won’t agree with you or with me, no matter what reality is. Most agree that a CJ-7 looks tough and are more along the lines of the iconic Jeep look, but the TJ’s more agreeably homely appearance hides a mechanical wolf as compared to the CJ-7. The fact is both can be built to do what you want them to. Some carry a little more style, while some have the benefit a little more modern design.

Speaking of an 1986 CJ-7…
I own a ’86 CJ-7 with a 21⁄2-inch Rough Country lift, and a 2-inch body lift. It’s a pretty solid truck, and I’ve brought the steering up to modern standards with a tie rod flip, heavy-duty tie rods, steering box bracket, steering box brace, and a Flaming River input shaft. My only complaint is that the brakes are subpar, though everything is fairly new, i.e., discs and pads. The Jeep has manual brakes with just the basic master cylinder with no booster. My question is, which upgrade route do I go with, dual diaphragm brake booster or hydroboost? I know hydroboost is more, so being able to stop quickly is a must, especially with the way New Yorkers drive!
Roy Winn
Brooklyn, NY

Somehow in the past 15 years of playing with Jeeps I have never messed with converting a Jeep to hydroboost, but I have heard only good things about the stopping power it can add to a Jeep. The only complaints I have heard are that a conversion ain’t cheap, and you have to know what you are doing to piece it together using only junkyard parts.

I am a little surprised that your ’86 CJ does not have a power brake booster—if I am reading your letter correctly and that is indeed what you are saying. It seems like the stock system might not be up to snuff if you are running 35s, 37s, or larger tires, but with a 21⁄2-inch lift and 2-inch body lift, I doubt you are running tires that large. If that is correct and your Jeep does not have a brake booster, I would definitely try tracking down the parts from an ’86 CJ-7 that did have a brake booster and try that first. That will be the simplest and cheapest route. And you may be able to track down new or remanufactured parts from your local parts store. If you have your heart set on hydroboost, getting an aftermarket conversion kit for hydroboost is probably the way to go rather than searching junkyards and harassing parts counter people. Try Vanco Power Brake Supply at 800/256-6295, ( for a conversion kit.

Outsmarting a 2012 JK
Any idea about the programmers or tuners for the ’12 JK that will allow me to bypass the low-range-only use of lockers, on/off of stability control, idle speed, adjust for tire size, and turn off the low tire pressure monitors? I may be wrong, but some of the ads in Jp only show those options for ’11 JK and back, with ’12-’13 being for engine performance only.

Apparently the Bully Dog GT (PN 40440) for Jeep can do everything you want for the ’11-’13 JKs. This unit also comes with tuning programs and gauges. Have a look at Bully Dog’s website at: for all the details.

Hee, Hee, Hee, He Said Bung!
In the March ’13 article about a high-clearance skidplate (“Clearance Clarence”), you had to weld in two new threaded bungs for the new skidplate to fit. I have a ’92 YJ with rotted out T-case crossmember bungs, and my homework skills are terrible. I can’t find where to order these bungs! Stupid question? Any help would be great.
Josh Wright
Frederick, MD

Sorry for the title of this letter, I enjoy humor usually reserved for 7-year-olds. We got the extra weld-in bungs for that story directly from T&T Customs, and they may be willing to sell you some. I have bought similar weld-in bungs from McMaster-Carr ( Once there, search for “weld nuts,” and be ready to see more weld-in-bungs and/or weld nuts than you ever could imagine. You just need to know the diameter and thread-pitch of the bolts. The ones you want fit YJ and TJ skidplate bolts and are 1⁄2-inch 13-tpi. McMaster-Carr will have them for almost any standard or metric thread.

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