Click for Coverage
  • JP Magazine
  • Dirt Sports + Off-Road
  • 4-Wheel & Off-Road
  • Four Wheeler

Your Jeep - May 2014

Posted in How To: Tech Qa on April 22, 2014
Share this

ZJ Coils on a TJ Again
I saw the article on putting ZJ front coils under a TJ, and I was wondering if the rear springs were still stock on the TJ? Plus I have Rubicon springs on mine, but the front still sits too low. Not much, but I don’t like it so I am curious to try this out. Are there more pictures on how your TJ looks now?
Shawn Doyle
Via email

Yeah, I am running stock rear coils on my TJ with a set of .75-inch Daystar spacer pucks. Before I added the ZJ front springs, the Jeep was sitting nose low, mainly because the stock front springs were sagging. Now the Jeep has a bit of a nose high rake, but I like that look and it makes sense, as the rear does not rub (much) and the front tires require more space to allow turning while flexing. Here is another picture of how the Jeep sits now. I think the ZJ springs would provide a little more lift than the TJ Rubicon springs, as I have heard Rubicon TJ springs are good for about an inch over stock. I can’t confirm it, as I don’t have a set of the TJ Rubicon front springs here to test.

Manual Addict
Guys, your magazine rules. I mean, it’s straight-up-American, hair-on-your-chest, beer-in-one-hand, wrench-in-the-other fun! And I just renewed for another two years -- so maybe you can answer because I’m super loyal.

Speaking of hair on my chest and a wrench in my hand, I need some advice. My love for manual transmissions started before I could drive, so it’s inevitable that it would come to this. I did my first manual swap from an auto on a BMW racecar I drove, and that wasn’t too on to my next project.

I’ve checked the forums, and yeah, they’re okay for basics, but then you get the “Why would you want to do that!” guys who just want to stir the pot. And others who say, “Just buy a manual XJ.” To me, that defeats the point. I love my XJ, have owned it for years, so I’d rather improve it, not trade it for something else whose history is unknown. Plus, manuals are more fun, plain and simple, and part of the fun is saying, “Yeah, I did that.”

My Jeep is a ’99 with the 4.0L and AW4/NP242 combo. It’s fine as it is, but the project will be to fit 35-inch tires and build a sweet rig that I want to have more control over -- so the manual swap is what I want to do. I know the AX15 is a good option and I would want the NP231 in there, but with possible 21-spline to the 23-spline conversion I now have, I’m not sure what I would need. Can you give me a rundown of a swap like this and maybe help with things I have not thought of? I would greatly appreciate it. You rule.
Bryan Palmer
Via email

Merica! Need I say more! Well, Bryan, like you I am a manual addict. I’ll admit it. I’d rather row gears in almost any situation then let a slushbox do whatever it is that they do. Now having said that, the AW4 in an XJ is probably one of my favorite Jeep autos of all time. They are pretty bulletproof when taken care of and have a decent First gear ratio and a nice Overdrive. I can, however, understand your interest in having a five-speed in its place, but I do think the path of least resistance (especially if your Jeep is not highly modified) is to look for an XJ with a manual from the factory. Why? Well, swapping is gonna be a fair amount of work. You’ll need to find so many parts from a similar year XJ with a manual that you might as well buy it, if for nothing else, just to have all the parts. You are gonna need the the manual XJ ECU (or the Jeep will at least throw a check engine light), transmission, pedal assembly, bellhousing, clutch, flywheel, throwout bearing and hydraulic stuff, driveshafts, etc. You could use an AX15 out of an earlier XJ, or maybe one from a Wrangler (the T-case clocking will be different in a Wrangler), but you’ll still need the manual tranny, ECU from a similar year XJ, and all those other parts I already mentioned. If you want to go to a NP231, get one from a 4.0L H.O.-powered XJ with an AX15 (again, because of possible clocking issues) so the spline-count and stickout length match. While you’re at it, grab the T-case shift linkage as well.

I’m not saying you can’t do this swap, because I am sure you can. I’m just not sure it’s worth the effort when factory-equipped manual XJs can be found. If you decide not to do the swap, I’d look to trade into a ’95-’96. The ’97-’01s with a manual are gonna be few and far between, although they do exist. I had an ’01 with an NV3550 and an NP231 for a few years. One last suggestion is that if you have to do a manual swap and you wanna spend cash and start a major project, look into swapping to a NV4500. It’s big (may require cutting the floor), heavy, and getting rarer with the super low First gear, but it will add a granny First gear while retaining overdrive

Renix or H.O. Identification
How can I figure out if my ’90 4.0L XJ with an auto is running a Bendix- Renault (Renix) or H.O. fuel injection? It runs fine and it does not smell of fuel, but opening the hood I don’t have any information about the type of fuel injection. The Jeep does not have a C101 connector on the firewall.
Via email

Marco, if you are sure your XJ is a ’90 and not a ’91, then it should be running the Renix system. Our own Pete Trasborg reports that the Renix-to-H.O. change is pretty solidly between a ’90 and ’91 XJ. And he also says that yours could be Renix even without the C101 connector on the firewall, as the C101 was phased out in the ’89 model year. In other words, before the switch to H.O. injection. The easiest way to check is to look at the throttle body. If it has a square four-bolt pattern to the intake (shown), it is an H.O.-injected 4.0L. If it has a triangle shaped three-bolt pattern, you have the Renix injection.

Long-Arms on a CJ?
I was hoping to do a custom suspension on my CJ-7, but my problem is that I can’t find a kit I want to use. I was hoping to do a long-arm style on the rear, but I can’t find a long-arm kit for an ’85 CJ-- or any CJ for that matter. I found a kit for an ’85 Jeep Cherokee, and I’m wondering if the kit for the Cherokee will fit the CJ-7. If not, how much modification would have to be done to the kit and my Jeep for it to work correctly? I was also planning on doing away with the fan on the motor and putting an electric fan on it.
Hunter Boring
Via email

Hunter, there are a couple of routes you can take with your suspension dreams, but more on that later. First I am gonna answer your second question. I would not swap the mechanical fan for an electric one. A stock mechanical fan in good working order will reliably cool your CJ-7. If it is not, then you probably have other problems. Your radiator could be filled with junk, keeping it from cooling properly, or your water pump or thermostat could be malfunctioning. I’d start with those first, toss in some new hoses, a new fan clutch, and a good coolant flush and see if that won’t clear up any cooling issues.

Getting back to your first question, there are several aftermarket companies that can help get you started with a link-style suspension. Unfortunately a long-arm conversion for a Cherokee probably won’t help much because a Cherokee and a CJ-7 are very different designs. First of all, and I am not sure which long-arm Cherokee conversion you found, but Cherokees already have coil front suspension, while your CJ will have leaf springs on all four corners. Converting to a long-arm or link-style suspension will require lots of modification to the frame of your CJ and the axles. You could get a pretty good start with a three- or four-link like those offered by Synergy Manufacturing ( They have the parts to build the links and brackets for the frame and axle, but you’ll have to figure out how to mount coilovers, coils and shocks, or air shocks to complete the suspension and set the ride height. Oh, and welding…yep, you are gonna have to do lots of welding. Another more complete option is the Black Diamond Xtreme Coil Link Conversion System from Superlift Suspension ( This is a complete link and coil conversion available for a CJ designed a few years back, but in general the XCL is a pretty tall lift and yields a pretty soft suspension that some have called unstable because of the relatively narrow rear coil mounting points. If I were you, I would spend more time looking into modifying and improving your leaf-sprung suspension to perform better before getting too crazy with a coil conversion. If you want a coil conversion, find someone with a CJ that performs the way you want yours to and figure out what they did to it.

A Flattie and a Buick Walk Into a Bar…
Hello, I was reading your article about the headers in your ’49 CJ-3A. I think I have found a Buick V-6 for my ’50 CJ-3A, and I think that since you have already done this, you could save me from reinventing the wheel by telling me what you had to do to make the swap. Maybe there is an article you wrote on the project? How difficult a swap is it? Where did you get the motor mounts and what about transmissions and transfer case hookups? Any help you can give me will be greatly appreciated. I know this has been done a lot, and the CJ-5s came with the V-6. I just don’t know how much trouble I’m looking at to do my CJ-3A. Harry Hill
Via email

Harry, the Buick V-6 is a great mill to have in a flattie. The fact is the Spicer 18 transfer case is one of the coolest Jeep parts out there -- mainly because bolting on an external Saturn, Warn, or ATV Manufacturing overdrive allows for low axle gears that are great for crawling but still get reasonable highway speed thanks to the Overdrive. The problem is that this part, the Spicer 18, which allows so many gearing options is not up to the task of handling huge power. A Buick V-6 offers a pretty sweet package that fits well in flatties and early CJ-5s without totally overwhelming the internals of the Spicer 18 the way a V-8 can. Unfortunately, I don’t have an article on my own Buick V-6 conversion, but I can answer many of your questions. First you have to decide if you want an earlier odd-fire or a later even-fire Buick V-6. There are plusses to both, and either will make for a great engine in a flattie. Many people have swapped them between the fenders of a Jeep. The odd-fire (ranging from the early ’60s in Buick cars to ’65-’71 in Jeeps and then ’75-’77 again in Buick cars) has a huge, heavy flywheel that helps externally balance the engine with its odd…odd-fire system (pun intended). That heavy flywheel helps maintain engine inertia to build with low-end torque, keeping the odd-fire running even when lugged down to really low RPMs (like in rocks or crawling up hills). Problems with the odd-fire are that they are starting to get a bit long in the tooth, and usable used parts are harder and harder to find. Also, the odd-fire nature of the engine rules out some fuel-injection systems. The newer even-fire Buick V-6 is a bit more common in junkyards and can easily be fuel injected. And, HEI ignition is available from the factory. The even-fire engines are internally balanced and lack the super-heavy flywheel that helps the odd-fire lope up hills and all over the rocks, but parts are easier to find and the even-fire is still a brick poop house of a V-6. These even-fire engines can be found in lots of old boxy rear wheel drive Buicks, Oldsmobiles and the like both as a 3.8L (in ’78-’84 cars) and as a 4.1L (in some ’80-’84 cars) with a forged crank and an aluminum four-barrel intake. Either way, both Buick V-6s have tons of aftermarket support in the form of bellhousings, performance parts (like headers), conversion motor mounts, and so on. Many of these parts fit both even- and odd-fire, although some are specific. Be sure to verify before placing an order.

Basically, I got my ’84 even-fire 3.8L Buick from a junkyard from a wrecked Oldsmobile. I added a rebuilt HEI distributor from a ’79 even-fire Buick V-6 from the local parts store (the ’84 has some computer controls associated with the factory carb that I did not want to mess with). I then sourced motor mounts, bellhousing (to adapt the engine to a Ford T-18 transmission), pilot bearing, and adapters to retain the Spicer 18 T-case (behind the Ford transmission) from Advance Adapters ( I was also able to get a brand new-even fire Buick flywheel, clutch, pressure plate, clutch fork, and so on from Centerforce ( Add on a TBI injection system from Howell Engine Developments (, and I had nearly all the major parts for my conversion. That meant I was then able to install the Buick engine and Ford transmission in my flattie without having to spend lots of time scrounging around junkyards or swap meets to dig up parts that might not even fit. So, to reiterate, you’d have to decide odd- or even-fire and start tracking down some parts. Just be wary of any Buick V-6s built after 1982 and found in front-wheel-drive cars, as they may have a different engine-to-transmission bellhousing bolt patterns. Other good options for an engine swap in a flattie would be a Chevy 4.3L V-6 and a hand full of more modern four-cylinders.

Low, Low, Low Spicer 18 Follow-Up
I’d like to give Mike Gardner (Your Jeep, Oct ’13) another lead for his super-low, low range Spicer 18. In 2003 I had a 4.86:1 low range installed in my transfer case by a company called O’Briens 4 Wheels West. I just searched the Internet for them; they apparently don’t have a website, but their address is 1302 Hidden Court, Roseville, California, 95661-5882, 916/773-3278. I’m very happy with the conversion. This gearset eliminates the ability to use a Saturn or Warn overdrive, though, because of the small size of the input gear. I think you can use a Saturn Overdrive with the Tera Low gears -- some of them, anyway.
Dave Peterson
Via email

Thanks for letting us know about this! To be clear, TeraFlex’s website says their 18LOW does work with both Warn and Saturn Overdrives.

Write Us!
Got a tech question you’re just itching to get answered? Send it on in to Jp Magazine, Your Jeep, 831 S. Douglas St., El Segundo, CA 90245, or e-mail it to

Connect With Us

Newsletter Sign Up

Subscribe to the Magazine

Browse Articles By Vehicle

See Results