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Jeep Tech Questions - March 2009 Your Jeep

Posted in How To on March 1, 2009
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Grand Expectations
I've got a question about the front Dana 30 in my '96 Grand Cherokee. I know it's pretty weak, especially when it's got a 5.2L V-8 and those front CV axles instead of a standard U-joint (I know; I should have passed on it but it was a good deal). Well, since I'm on a tight budget a complete axle swap is out of the question. Would it be possible to swap the axles with standard U-joint axles from a junkyard ZJ? Do I have to swap knuckles too? I'm not too concerned about the ABS. I don't wheel it too hard and I'm only running 32s with a 3.5-inch lift GilbertLas Vegas, Nevada

I wouldn't tell you to pass on that vehicle. It's a good Jeep.

No need to swap knuckles. You can just slap in some ZJ replacement shafts from a U-joint type axle. If you can't find them in the junkyard, check Crown Automotive (crownautomotive.net) for stock replacements. They list the outers for use with your ABS under PN 4728984 (you'll need two) and the inners under PN 4740970 (right) and PN 4740971 (left). Don't forget the U-joints, PN 4137757, and I'd recommend installing new inner axle seals PN 4874477 since nearly every CV-equipped Dana 30 front I've encountered had hashed inner seals that will eventually start leaking.

With only 32s, I doubt you'll need the alloy shafts, but depending on Crown's price on the stock replacements it may not be that objectionable to get the upgraded alloy parts. If you can find a company who still makes them, that is. Check Alloy USA and Superior for starters.

Dig Dug Dead Bug
How can I clean the bugs out of my TJ radiator without damaging the fins?Matt SimkinsMidland, Michigan

There's a couple ways. First, you get a sharp dental type pick and sit there for hours carefully removing the bugs from between the fins. I'm not gonna lie to you. It sucks.

Second, you can get a "radiator comb" at certain auto parts stores. It's a short little steel, aluminum, or hard plastic comb with teeth spaced the same width apart as a radiator. Usually they have a few different sets of teeth in the same tool to work with radiators with differently spaced fins. The tools are primarily designed to straighten bent fins and won't really work all that well for getting the bugs out, but it'll be better than nothing.

Third, remove the radiator and submerge it in a solution of soapy water and let it soak for a couple days to a week. You're looking for the little bug bodies to decompose and get soft and mushy. Once that happens, shoot a blast of compressed air from the backside of the radiator to blow them out.

Hatari II
I just bought my fourth Jeep and was hoping you could give me your opinion on it. I bought it for $500 from a guy who bought it in the early '80s, drove it home and parked it in his garage and never drove it again. It's a '61 CJ-6 with 12,880 miles on it. The guy he got it from only used it for plowing his driveway in the winter and cutting his grass in the summer. It seems to be all original including the soft top and doors as well as the entire drivetrain with four shifter levers on the floor and a PTO. It's a four-cylinder and three-speed. The body is in rough shape from winter salt. I have been spraying every moving part with PB Blaster and am going to start changing plugs, wires, gaskets and fluids. Would you do anything else before hooking a battery up and turning it over?Scott MorrisGrand Rapids, Michigan

Wow, that's a great find at an excellent price. You've got a 134 F-head engine, T-90 transmission, Spicer 18 T-case, Dana 25 front axle and Dana 44 rear axle in that thing.

For starters, spray the spark plug threads down with penetrating lube 'cause they may be seized. You don't want to snap one off in the block. Once you pull the plugs, shoot a little Marvel's Mystery Oil through the plug holes inside the cylinders and let it sit for a few days before you try to fire it up. That'll help free up the piston rings from the cylinder walls. It's okay to fill up the cylinders with Marvel's as long as you don't have the plugs in the first time you try to crank it over. If you have the cylinders full of fluid and then cap them with the spark plugs the engine will hydro lock and bend a rod.

With the cylinders soaking, pull the oil drain plug and oil filter. Wait until the engine oil stops draining, then pour two or three more quarts of fresh oil through the engine and let it drain through. That will help flush out any debris and sludge from the pan. Fill the engine crank case with fresh 30W oil. You may want to substitute one quart of ATF for one quart of engine oil for the first fire up to help clean the oil passages and free up any sludge. ATF has a much higher detergent content than regular auto oil and adding one quart won't hurt the engine. Also, toss on a new oil filter.

I'd also drain the tranny, t-case, and axle lube since 20 years is a long time to sit. Don't forget the engine will cause the tranny input shaft to spin even if it's in Neutral, so it's a good idea to have fresh 90W in there.

Remove the fuel tank from under the front seat (at least I assume it's under the seat) and drain any fuel that may be in there. It's not going to be any good. Replace the fuel filters with new ones (or add filters if there aren't any already in place). Grab a carb rebuild kit from NAPA, Crown Automotive (crownautomotive.net) or 4WD Hardware (4wd.com), and pop the top of the carb off. Shoot some carb cleaner in the fuel bowl to get rid of any varnish and sludge and shoot carb clean into the carb body.

Remove the distributor and spin the oil pump drive with an electric drill and attachment to index the oil pump drive to build oil pressure. You don't want to just crank the engine to build oil pressure since the bearings, rings, and valvetrain will most certainly be dry after all that time. Running the pump with a drill builds pressure and gets oil shooting through the galleys without any of the engine components moving.

Pull the spark plugs and crank the engine over a few times to shoot any Marvel's oil out. Make sure there is coolant in the radiator. Spin the plugs back in, prime the carburetor with fuel, and fire it up. I'd let it come up to operating temperature for about 10 minutes, then I'd do another engine oil and filter change just for safe measure with 10W-40 or 20W-50 depending on your climate needs.

Trading Up
I am in the Navy and am currently deployed on the USS Iwo Jima. I own a '99 TJ SE and was planning to swap the four-cylinder engine, tranny, t-case, and axles with some of the money I have saved. After looking into it, I have changed my mind. I am now looking for a Rubicon. Do all Rubicons come with Dana 44s front and rear? Are there any other models that come with Dana 44s front and rear? I want a Jeep that is very strong and that I won't have to worry about breaking during mild trails. Adam Whitt, Slapout, Alabama

Finally, a question from somebody who makes sense! You're right, it really doesn't make financial sense to swap the engine, tranny, t-case, and axles in a base model TJ when you can buy a Rubicon loaded with factory front and rear lockers, low range t-case, and a decent amount of options. The Rubicon models were/are considered higher end trim levels, so most of them came with A/C, cruise, and other niceties your SE doesn't have.

Yes, all TJ Rubicons have front and rear Dana 44 axles with 1.31-inch, 30-spline axleshafts. They also came with 4.10 axle gears, a front electric locker (locked/open), a rear electric locker (locked/limited slip), and a factory 4:1 Low range in the upgraded NVG241 t-case. Regular TJs have a NVG231.

I see used '03-'06 TJ Rubicons going for anywhere from $12,000-$20,000 down here in So Cal, so I imagine it's similar across the rest of the country. I would highly recommend looking for a '03 or '04 model with a 5-speed (it'll be the excellent NV3550) since the automatics aren't stellar performers off-road and the NSG 6-speed that came in the '05-06 models isn't as burly as the 5-speed. The only downside to the drivetrain components in the Rubicon is that the axles share the smaller, relatively weak axle tubes of the pedestrian TJ's Dana 30 and Dana 35. This only becomes a problem if you get abusive (jumping, for instance) or run very large tires (37-up) in hardcore rocky terrain. However, Dynatrac (dynatrac.com) is putting the wraps on a replacement axle housing with heavy duty tubes that accepts all the Rubicon knuckles, brakes, gears, and components.

Ideally, for what you're looking to do, I'd consider an '03-'04 TJ Rubicon. Add a simple 2-inch spring spacer lift and throw some larger 265/75-16 (roughly 32s) or 285/75-16s (roughly 33s) on the stock rims. The Rubicon rims are excellent pieces that are very strong, coated for brake dust resistance, and look good too.

Juice Goose
I opened up the Nov '08 issue and flipped to your "25 Most Asked Questions" article. When I spotted the question about disc brake conversion I got all excited. Then I realized you were talking about the early CJs with closed knuckles. My Jeep is a '73 CJ-5 sporting a worked-over Chevy 283, TH350 trans, and open knuckle Dana 30 front axle. My question is, will the same procedure work on my Jeep, minus the grinding on the knuckle, or am I stuck with crappy drum brakes? This poor boy can't afford $1,000 for a conversion kit. Will I be able to use my stock master cylinder or will I need to change over to one with a booster and larger reservoir?John McClune,via e-mail

The same conversion will work on the '72-'76 Jeep open knuckle Dana 30. The spindle stud holes are clocked slightly different on the Dana 30 knuckle, so the caliper will be in a slightly different position, however everything will bolt up. If you want to clock the caliper in the same orientation as the Chevy/early conversion you can redrill the GM caliper bracket pretty easily.

You've got another option regarding getting disc brakes on your Dana 30. You can also look for a '77-'81 Jeep front axle with factory disc brakes and then transfer over all the components from the knuckle-out. Or, if the junkyard axle has the same ratio as your current axle, just bolt the whole thing in your Jeep. Jeep went to a wider front axle in '82, but the '82-'86 Dana 30 front will still bolt in. You can run rear wheel spacers to make up the track width difference if you like.

You can keep your master cylinder, but you've got to remove the residual pressure valve from the front port. Trace the hard lines that go from the front brakes to the master cylinder to determine which line is for the front brakes. It's usually the rear line. Remove the hard line for the front brake from the master cylinder. There will be a conical brass fitting pressed into the bore. Screw a drywall screw into the brass fitting (not too far, just enough to have it grab hold) and yank out the brass fitting by pulling on the screw with a pair of pliers. With the fitting removed, you'll see a rubber plug in the bore. Remove it and the spring that's behind it with a pair of needle nose pliers. Clean up the brass fitting with some fine sand paper and tap it back into the master cylinder hard line bore. Then screw in the hard line for the front brakes back on the master.

The residual pressure valve keeps some pressure on the drums so the drum cylinders can more quickly overcome the force of the shoe retaining springs when the brakes are applied. Disc brakes don't need this residual pressure and unless you remove that little valve in the bore of the front brake fitting the disc brakes will drag as the vehicle is driven.

Solid Plan
I currently own a '99 TJ that sits on 33s with a 3-inch suspension lift and a 1-inch body lift. I'm planning on going to a long arm suspension and will be perfectly happy running 35s. My buddies are telling me to go with at least a 5.5-inch lift so I can eventually run 36s or 37s. I'm a firm believer in keeping the center of gravity low and I'm thinking that a 4-inch long arm with 35s will be the best bet. I'm eventually going to go with some tube fenders but I'm not in any hurry until the stock ones get mangled. I've already cut the front fenders into a flatfender look and the clearance is great with 33s.

What I'm getting at is which lift height do you think will be right for me? I truly believe the axles will be able to handle the 35s. They are the stock Dana 30 front with a Lock-Rite and an upgraded Super 35 kit with a Detroit Locker in the rear. I've never had any problems with them and my driving style is very light on the pedal while the Jeep does it's best to crawl over everything. Will Coburn, via e-mail

I think you're right and your friends are wrong. I like your idea about keeping your CG low. The long arm with only 4-inch springs will be very stable. You'll like it. You should be able to squeeze the 35s under there with no drama.

If/when you ever do decide to go to 37s I'd look into a Gen Right Off Road or other manufacturer's corner protection for the rear and would cut/raise the rear fender openings. Then do the high clearance hood/tube fender thing up front. AEV and Gen Right make versions of what I'm talking about for the TJ. With the aftermarket support for TJs the way it is nowadays there's no real good reason to lift a Jeep to the moon unless you're just going for looks.

As for your axles, it's all up to you whether they last or not. I'm not a big fan of the Dana 35, but that's not to say you can't keep it alive if you're careful. I know some guys who do, but most don't. Sounds like you've got the basics down, though. Keep out of the throttle when bound and be careful with tire placement.

Squeeze Play
I've been looking at the Mastercraft or the heated Bestop replacement seats but the chief of the finance department gives me the "too much $$$ look." So, I'm thinking we will end up with either the Smittybilt or Rugged Ridge seats. Are there any clearance issues with Tuffy Security center consoles that you know of in a YJ? Jerry McDavid, via e-mail

I ran the Tuffy console in my YJ with Bestop Trail Max seats and had no issues. You should be fine with either of those replacement seats.

Got a tech question you're just itching to get answered? Send it on in to Jp magazine, Your Jeep, 6420 Wilshire Blvd., Los Angeles, CA 90048, or e-mail christian.hazel@jpmagazine.com.

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