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November 2010 Your Jeep

Posted in How To on November 1, 2010
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Dana Dropping
I just inherited a '99 Cherokee Sport with the 4.0L and automatic tranny. I don't know what kind of maintenance has been performed on it in the past, so I am in the process of replacing all of the fluids, tuning it up, and so on. How can I tell which rear axle I have? Also, how can I tell if it has a Trac-Lok differential or not? If it does have a Trac-lok, what is a suitable friction modifier that I can use? Attached is a picture of the differential. The outside diameter of the tubes is just a bit larger than 3 inches. Does the Jp magazine staff have a preferred brand of gear lube?
Matt Williams
Mercersburg, PA

Since you probably want the lube before you pop the diff cover for inspection, put the transmission in Neutral and with the rear wheels off the ground spin the tires. If they go in the same direction, you've probably got a Trac-Lok. If they spin opposite, it's an open diff-or the Trac-Lok is completely wasted.

There are lots of nice synthetic lubes, but I usually run conventional Valvoline oil in anything I care about. Both Car Quest and NAPA in-house oil brands are actually just Valvoline oil, so if you've got one of those stores nearby you can just buy the NAPA- or Car Quest-brand lube.

As for friction modifier, most hypoid lubes including Valvoline comes with the modifier already in it. However, if the lube you buy doesn't say "for use with limited-slip differentials" on the bottle, you can swing by the Jeep dealership and buy a container of Mopar friction modifier, PN 04318060AB.

360 Turnaround
Greetings from Sherwood Forest: the legendary home of Robin Hood in merry old England. I have a '78 CJ-7 with an AMC 360 engine. I also have a spare AMC 360 engine to rebuild. Do you have any suggestions as to the best spec for an engine rebuild on a modest budget? Full MPI is outside of my budget, but higher compression pistons, a different cam, and a four-barrel manifold and carburetor are a possibility. I use the CJ for gentle off-roading and general cruising, so a modest power boost with plenty of mid-range torque would be ideal. You have probably covered this before but I have not found it in my back copies of Jp.

For your information, my CJ has the standard Quadra-Trac T-case and axles (AMC 20 in the back) with 4.10 gears, 31x10.50R15 tires, a 1.5-inch body lift with heavy-duty shackles, a later roll-over bar, and a period-correct Ramsey REP8000 winch. It spent some years in Switzerland and Ireland before arriving in the UK in 2004.
Brian Smeeton
Sherwood Forest, UK

If you're only looking for a moderate bump in horsepower I'd think about simply adding a camshaft, intake manifold, and good four-barrel carburetor to your current 360. Here are my recommendations:

Camshaft: Summit Racing's PN SUM-K8600 cam and lifter set (duration @ 0.050 214 intake/ 224 exhaust; lift 0.472 intake/ 0.496 exhaust). This is a bargain-basement selection price-wise but won't skimp in the power delivery. It will give you a good bump in power, especially in the mid-range rpms and more power elsewhere in rpm range. Or, if you want something a bit rowdier with more of a lope, more mid-and-upper rpm power, Summit's PN SUM-K8601 cam is a beast (duration @ 0.050 224 intake/ 234 exhaust; lift 0.496 intake/ 0.521 exhaust).

Intake: Most will suggest an Edelbrock Performer intake manifold, but I've found you give up very little, if any, low-end by choosing the Edelbrock Performer RPM. Either the standard RPM or RPM Air Gap intake will give you very similar low-end performance as the standard Performer manifold, but with a big mid-and-upper rpm bump in power. At the top end the RPM is probably worth 15-25hp over the Performer.

Carburetor: You'll get more top-end power (probably 10-15hp or so) with a 750cfm carb, but you'll get much better drivability with a smaller 600-670cfm carburetor. I'd consider the 670cfm Holley Truck Avenger. They deliver decent performance and very good off-road drivability. Otherwise, find yourself a good, used Q-Jet. Or, Summit Racing sells rebuilt Q-Jet carburetors such as its PN SUM-210216 750cfm electric choke model. The Q-Jet has smaller primaries that keep the low-end/slow-speed intake air charge velocity high, but the cavernous secondaries still deliver a huge whack of fuel when needed. Plus, they're the best off-road carbs going in my book. The downside is that they're difficult to initially tune for a performance application.

Distributor: I know it's often overlooked, but seriously consider upgrading to a Performance Distributors DUI HEI distributor. It'll make a noticeable difference. In fact, consider making this modification to your stock engine first and then determine if you even still need/want more power!

Put your savings into upgrading your rear axle with some 1-piece shafts because with the additional power they're likely to snap where the hub presses into the keyed shaft splines.

If a rebuild is required, you can find a set of Keith Black Hypereutectic pistons that can deliver a 9.5:1-10:1 compression ratio depending on head gasket and machine work (block and head decking). Piston compression/head volume and head gasket thickness will be the final determination on what your actual compression is. Once your machine shop cc's your head chambers, measures your block, and determines how much needs to be cut from the head/block faces you'll get a better idea on what pistons you'll need to order to reach your target compression. If you shoot for a true 9.5:1, you'll have decent quench, good throttle response, and should still be able to avoid costly premium fuel, since AMC engines are somewhat more resistant to detonation than other brands.

Plucking Wallflowers
How do you properly put a Jeep back on the road? I have a '98 TJ that I bought new. I have every receipt from all work done and parts added. I have babied her since day one. She has sat in the driveway for two years and I am now ready to put her back on the road. How can I do it best, minimizing damage to the engine and other components?
Jay Siller Staten Island, NY

We covered this in the March and April 2009 issues of Jp magazine using my '89 YJ that sat for two years ("Why-J," Parts 1 and 2). Here are some highlights. 1) Clean battery cables and (most likely) replace the battery;

2) Check the level and condition of the anti-freeze and radiator/heater hoses;

3) Pop off the cap and rotor and make sure they didn't get corroded from moisture under the cap;

4) Remove the spark plugs and spray a bit of fogging oil into the engine. That'll help protect the rings on first cranking the engine. Normally I'd say to use Marvel's Mystery Oil or something a bit heavier, but it's a newer Jeep and two years isn't that long in the grand scheme of things. The fogging oil is available at your local Napa. If they don't have it, check your local boat/marine supply shop. Fogging oil is most commonly used when winterizing a boat;

5) Drain the oil and spin on a fresh oil filter;

6) Remove the fuel cap and smell the gas. If it's got a sweet scent or smells like varnish, add a can of octane boost and/or fuel injector cleaner. Top off the fuel tank with high-octane fuel the first chance you get. Then the next tank, fill with 89-octane. Then you can go back to running 87-octane (assuming that's what you used to run in it);

7) Turn the key on/off a couple times listening for the fuel pump to shut off before cycling the key again. This will build fuel pressure and prevent excessive cranking;

8) Fire it up. Keep and eye on the oil pressure. Honestly, you should be fine. I'd consider maybe changing the oil after 100 miles of so if the oil that's in the engine from storage looks really dirty. Pop the diff cover fill plugs and make sure that condensation didn't create excessive moisture in the diffs. You may consider changing the tranny, T-case, and axle lube, but it's not 100-percent necessary. It'd be more for your peace of mind.

Dana 35 Ponderings
As an avid reader of Jp magazine, I pretty much take your advice on several subjects while I build my '91 YJ, but something caught my eye on your Project Why-J that I just have to question. You guys are always saying what a dud the Dana 35 is and that you shouldn't modify or put a locker in it. But I noticed that the Dana 35 on Project Why-J has an Eaton E-Locker. This contradicts the sage advice given.

Now to my main point: I am building my YJ as a daily-driver with mild trail abilities for the mountains of Colorado with no rock crawling capability. I plan to run the Dana 30/Dana 35 axles with 4:10s with 33-inch tires, and a mild lift for clearance. I also plan to place a Detroit Truetrac in both front and rear for a little extra traction, which the current open differential really lacks. The Truetrac has received good reviews by you guys and the rest of the Jeep community, so that's good enough for me. In addition, I plan to replace the current axleshafts with new units and keep the old ones for spares should the "expected" happen.

This build will run about $2,400, which is still less than a new Dana 44 (less install charge) and because I don't have the time or welding ability, a Ford 8.8 swap is unlikely. So, is this a reasonable plan for a daily-driver with limited trail use and conservative skinny pedal, or should I seek out a local shop and have them swap in a Ford 8.8 which will still cost over the $2,500 mark?
Dave Martinez
Englewood, CO

I hate to break the bad news, but up until recently Jeep Outfitter (jeepoutfitter.com) was offering a brand-new Ford 8.8 axle assembly ready to bolt into a YJ for $1,079 that included 4.11 gears, a Trac-Loc diff, disc brakes, and YJ mounting hardware. You probably needed to purchase a new flange to adapt the YJ 1310 (or 1330) driveshaft U-joint since the Explorer axles come with a CV flange. Point is, there may be a few of these still floating around that haven't been installed, so it's worth doing a few nation-wide eBay and craigslist searches before you pull the trigger on any Dana 35 upgrades.

As for my Why-J build, I intentionally kept the Dana 35 so I could perform some long-term durability testing. It's fully-built with every whiz-bang component offered in the Superior Axle & Gear catalog including the company's 30-spline Super 35 kit with the Eaton E-Locker, the company's bolt-on Super Truss, 4.88 gears, and more. With the gear setup and installation said there's roughly $2,500 in my rear axle alone. It's survived for the most part, but I only run 31-inch tires behind the stock 2.5L engine. I'm pretty sure as soon as I feed it any real power from a V-8 swap I'm planning the ring and pinion will be chucking guts. The axle has had some issues: The backing plate broke and allowed the brake shoes to rotate inside the drum. Also, the housing isn't exactly true so the driver-side rear tire exhibits uneven wear. It's not perfect, but it is what it is.

To your plan of running 33s and 4.10 gears, I think if you try to use Overdrive you'll hate it. Kiss Fifth gear goodbye and practice your emergency downshifting. I'd rather see you running 4.88s in the stock axles or 5.13s or even 5.38s with an axle swap that supports these gears. A 2.5L with 33s will have an especially hard time since you'll be in the mountains of Colorado. If your Jeep is a 4.0L the 4.10s will be livable, but 4.56s or 4.88s would be better. The Truetrac diffs are great units, so there's no problem there. I'd guess you'll have decent luck if you upgrade the rear shafts to aftermarket alloy units and keep your head during climbs. You'll still be rolling the dice, but the Truetracs should help survivability over a true locking diff.

Trashcan Color Palatte
In your July '10 issue the cover vehicle was the NUKiZER M-715. The article was written by Christian Hazel. When I first saw it I fell in love with the color of the vehicle, and since I am almost in the painting phase of my '90 YJ build, I have to ask what is the color? Is it a custom mix or do you have a code? Please help me out here. I need to find this color.
Mark Doesburg
Amsterdam, NY

Chrysler's Mark Allen told us that it's actually off of a trash can they had in their shop. They grabbed the trash barrel, wheeled it into the paint guy's office and said, "Match this up." I'm pretty sure that trash can gray won't appear on any paint code. Sorry.

The good news is that it was a fairly standard industrial barrel like those found at most schools, hospitals, and other institutions. Next time you see one of those big 40-50 gallon barrels on caster wheels, steal it-cause that's your color!

Trasborg Electrical Tirades
We are getting ready to install new L.E.D. lamps in our '98 TJ. I remember reading sometime back about this causing problems with the flashers on the vehicle. You had repair for this in Randy's Electrical Corner. I've looked and can't seem to find it. Could you please go over this again for all of us out here who have decided to make this change or at least tell us where to look in back issues? One last thing. Are there any other things to watch out for when doing this change to the lighting system? Thanks in advance and keep up the great work.
Brad Deckard
Bloomington, IN

Pete Trasborg replies: For the '98 TJ, it is pretty easy to "fix" the flasher so that it won't flash fast when you put LED taillights in. The fast flash "feature" is to tell the driver that a light is out. To bypass this function, you have to remove the flasher from the steering column and simply score or cut a trace on the circuit board inside the flasher. I've done this with a pick or even my pocket knife before.

More info and pictures can be seen here: http://www.stuoffroad.com/electrical.asp.

For LED taillights, that is the only change to the vehicle that is needed.

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 christian.hazel@jpmagazine.com.

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