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May 2009 4x4 Truck Repair & Tech Questions - Tech Line

Posted in How To: Tech Qa on May 1, 2009
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Ford Explorer Gears and Cheers
Question: In Techline (Dec. '08), you stated that the Ford Explorer was available with either a 3.27 or 3.73 gear ratio. This is incorrect. The Explorer was always offered with either a 3.55 or 3.73 ratio. The 3.55 came standard (still does) on V-8 models as well as V-6 models without the towing package or the off-road package.

In other Explorer news, you also spoke of the manually shifted BorgWarner 13-54 part-time transfer case. The manually shifted version was the exact same as the electronically shifted version with the exception of the back of the case, where the shifting mechanism was. I don't know if this is the case for newer Explorers, but I do know that all of the transmissions that went into 4WD Explorers had the mounting locations for the shifters on the back, regardless of the shift type. The first-generation Explorers have a section about how to use the manually shifted transfer case in the owner's manual.

And keeping with the Explorer theme, I have one more question. I'd like to convert to rear disc brakes in my '91. I know that the 8.8-inch axle was offered in some models with disc brakes, so couldn't I just take the rear brake assembly off of a disc-equipped model and run it on mine? Which models of Ford trucks/SUVs had rear disc brakes on an 8.8-inch axle?
Jon Geddes
Everson, WA

Answer: All I can do is go by the material that I have, so I just double-checked some factory service literature and it states that the Ford Explorer from '92-'95 used a 3.27 or a optional 3.73. In '96 they changed the option from the 3.73 to 4.10 and stayed with the 3.27 until at least '96. Perhaps you have some sort of Ford factory information that I have not had access to that you would like to share?

As to the 13-54 transfer case being electric or manual shift, unfortunately, I don't have a wide range of Explorers to crawl under to look at shift linkage. As I stated, I couldn't find any direct reference but my great source, Bob Hutchins of All Transmission in Portland, Oregon, did confirm that there were some manual-shift units available. Being that the electric version appears to be also wired through the computer, it just might cause some major issues if all one did was swap out the shift linkage from electrical to manual. Guess the only way to do it would be to make the swap and hope for the best. Not something that I want to tell a reader.

As to the disc-brake swap, the '90-'94 Explorers had 10-inch brakes. In '95 they switched over to disc brakes. Will these disc brakes bolt on? Sorry, I don't have a clue. If I wanted to do it, I would pull down one side and do some measuring, maybe even make a paper pattern of the flange and then head to a salvage yard and do some comparison. You might also want to check with Master Power Brakes (888/351-8785, and TSM Manufacturing (303/688-6882,, as I believe they sell disc-brake kits for the 8.8.

Wants GM 10-Bolt Beefing Tips
Question: I have a few questions about a GM 10-bolt axle. The axle is in a '93 Chevy K1500 that has about 215,000 miles on the original ring-and-pinion and axleshafts as well as the leaf springs. What can I do to make it stronger (gears, shafts, seals)? What type of leaf spring can I use? Can I stuff a 3/4-ton leaf spring on without welding or modification? Are there any mid-range priced upgrades that a college student can afford? The truck has the ability to tow and haul junk. I want a heavy-duty truck without sacrificing the smooth ride. The truck is going to be converted to a mud truck when I graduate from college.
Mike Fox
Clio, MI

Answer: Questions like these always confuse me to no end. Mainly because I can't read between the lines and decide what the reader really wants out of his truck. If your truck has lived this long on the original driveline parts, why do you want to make it stronger? Apparently you're not abusing your truck. Yes, you can put on 3/4-ton springs but all that will give you is a stiffer-riding 1/2-ton, not the capacity of a 3/4-ton 2500 series. Most likely the frames are about the same, but with the 2500 series you get a larger rear end. While the front axle is still a 10-bolt on a 3/4-ton, you get bigger brakes and spindles.

As to improving what you have, well there are aftermarket axleshafts (check out our advertisers) and U-joints that are considerably stronger than the factory parts. As to gearing, it depends on what size tires you have in mind. Let's say 4.10s for up to 33s and 4.56 for 35s. I really would not recommend going with a tire any taller than that using the K1500 running gear.

You say you want to turn it into a mud truck at a later date. Does this mean competition? Are you talking about tires taller than 35 inches? Then by all means, you want to switch over to 1-ton running gear that will give you a Dana 60 front and a GM 14-bolt rear. These are basically a direct bolt-in conversion. Even with these, you will eventually want to spend a lot more money for better axleshafts, lockers, crossover steering, hydraulic rams, and such. There is no end in sight when you don't have goals that you want to achieve.

Keys Get Stuck In Isuzu Ignition
Question: I have an '02 Isuzu Rodeo LSE 4WD with the 3.2L V-6. Last night, the ignition key would not come out of the ignition switch. I tried shifting the transmission back and forth, in and out of gear, but no matter what I did, the key would not come out. Can you tell me what I am doing wrong?
Jeff Scott
Los Angeles, CA

Answer: Well, by the time you would have read this in the magazine, your vehicle most likely has been stolen because of the key being left in the ignition while parked. So I hope you read the email answer I sent you.

Seems that this is a common problem for this particular vehicle. It's caused by either a bad lock cylinder or the shift lock cable being out of adjustment. Gaining access to the switch is quite difficult, with lots of work just getting the dash panels off. It's really a job for your dealer unless you have the dexterity of an acrobat. So your best bet is to drop the vehicle off at your nearest dealer on the way to work and let them have a go at it. OK, if you really want to try and fix it yourself, then hit the service department and ask them to be nice and print you off the service bulletin that covers this. Without the proper instructions, it will be a nearly impossible job.

Pop Goes The Driveline
Question: I have a '76 Jeep Wagoneer and a '79 Jeep J-10. When I am under hard acceleration or my tires are spinning, like in mud, I get a popping sound. I have replaced the rear axle in the Wagoneer and I have checked the chains in the transfer case in both trucks, and they still do it.
Josh Gess
Carthage, MO

Answer: Sometimes a "popping" noise can come from a bad U-joint or a missing tooth on a differential gear. But in your instance, it's a pretty good guess on my part that the noise is emanating from the transfer case. You didn't say which transfer case your Jeep has, which could have come with either the Dana 20 or the BorgWarner Quadra-Trac. With the Dana 20 being geardriven, and since you said you had checked the chains, that tells me your fullsize Jeeps are using the Quadra-Trac transfer case.

Let's start with the chain. Just how did you check it? The correct way is to remove the transfer case's chain inspection plug and insert what Jeep refers to as a "thread chain tension gauge" (PN J-25162). Actually, this is nothing more than a plunger that pushes against the chain and measures the amount of slack in it between the drive and driven gears. Good luck in finding one of these gauges.

Otherwise, I have no idea how to tell you how to figure what the proper tension is supposed to be. When there is not enough tension, due to wear in the chain's links, the chain will actually jump teeth on the drive gear with the resulting popping noise. If this is allowed to happen over an extended time period, then there is a good chance that the drive gear will have to be replaced.

There could also be another source of the noise related to the transfer case. Instead of a viscous coupling, like most full-time units now use, this transfer case uses a cone clutch assembly. When a preset amount of torque is applied to them, they slip, allowing the wheels of, say, the front axle to go faster or slower than the rear axle. These cones sometimes exhibit what's referred to as a "stick-slip" condition. The sudden release of the cones will cause a clunking noise. This usually doesn't happen in straight-line driving, but will be evident when turning, or, as in your instance, when in mud and a tire starts to spin.

Several things can cause this problem.

Uneven tire diameter: You have to be dead-on with equal tire diameter. All the tires have to be the same size, and in reality, the same manufacturer, the same tread design, equal amount of wear, and the tire pressure has to match the load carried by each tire. This may require higher pressure in, say, the rear tires if a heavy load is carried in the pickup bed. Some people I know have actually made themselves a height gauge to check this, but a level on top of the tire and a tape measure work fine.

The next problem deals with the use of the proper lubricants. You just can't use ATF, motor oil, or gear lube, as this transfer case takes a special Quadra-Trac fluid. If by chance you have not been using the proper fluid, then you need to drain and refill the transfer case with this special fluid. Then find a paved parking lot and drive the Jeep in both tight left- and right-hand circles for at least five minutes in each direction. This should hopefully solve that problem. Just as a note, this stick-slip condition sometimes will exist when the vehicle sits parked for an extended period of time, but after being driven for a few miles, it should go away.

If none of these measures helps, you might want to do what's referred to as a "torque bias test." Put the transmission in Neutral and be sure what Jeep refers to as the "emergency drive" is not engaged. Chock the front wheels and apply the emergency brake. Crawl under the vehicle and remove the rear driveshaft at the transfer case. You're going to need someone to apply the brake so the Jeep can't move. With the proper socket on a torque wrench, try turning the rear yoke retaining nut in a tightening direction. The release point at which the yoke turns should be between 80 and 170 lb-ft. If under 80, the clutch cones need replacement. If over 170, it's a pretty good sign the wrong gear lube has been used and it needs to be replaced.

There are some parts available for this case, but not a lot. A couple of sources are Novak Conversions (435/753-2513, and Quadratec (800/745-2348,

304 To 350 CJ Swap: What You Need
Question: I have recently purchased a '76 CJ-5 with a 304 under the hood. I want to put a mildly built 350 in it, but don't know what all will need to be done. Obviously, upgraded axles and probably the transmission, driveshafts, and so on. My main question is, what did the Jeep come with from the factory? Transmission, axles, transfer case, and gears are all unknown to me. Any and all help will be greatly appreciated.
Scott Heileman
Alvin, TX

A The year 1976 was good for Jeep as they redesigned the frame to make it considerably stronger, both in torsional and bending loads, and redesigned the floor and dash panel for more legroom.

Let's start with the engine. The 304 is an AMC-designed motor and is in the same family as the 360 and 401. A 401 is a direct bolt-in to replace your 304. Now don't sell these motors short, as they can be made to run quite well. While the 401 gains you almost 100 cubic inches, it also comes with a steel crank and steel rods-nice things to have when building any performance motor. OK, you can easily swap to a small-block motor and be like everyone else, or start looking for a 401-incher. If this is the way you plan to go, then take a look at Planet Houston AMX (, which will give you the proper casting and cylinder head part numbers. In fact if you Google "401 AMC motors," you will find a huge amount of information on them. Just because they haven't been built for quite a few years doesn't mean that you can't find parts for them. Lots of stuff is still available, and Edelbrock ( is even making performance aluminum heads for them.

Naturally you can easily install a small-block Chevy as it's a common swap. Both Advance Adapters ( and Novak Conversions have all the pieces that you would need.

Your transmission, most likely (according to my factory Jeep service manual), is a T-150, but lots of other references refer to a T-14 as the standard three-speed transmission. Either way, parts for them are getting scarce and either one is not the best, strengthwise or gearwise, with only a 3:1 First gear ratio. You may have gotten lucky and have the super-strong optional T-18 four-speed. This trans had a 4:1 First gear and can handle just about all the power you can put to it.

Jeep trucks had what was a "heavy-duty option," which was the same basic T-18 but with a much lower and viable First gear of 6:1. If you should run across one of these transmissions, be sure you get the matching bellhousing as there were quite a few different bellhousing/input shaft length combinations used over the years. Jeep offered a special version of the GM TH400 automatic but only in the longer-wheelbase CJ-7s. While you can swap to the auto-shifter, the CJ-5's short 84.5-inch wheelbase makes for an extremely short rear driveshaft along with a steep angle-unless, that is, you go with a custom high-pinion rear end.

The transfer case is a Dana 20 with a poor 2.03:1 low-range. However, there are kits to allow a 3.15:1 ratio to be swapped in.

In '76, Jeep swapped from the great Dana 44 to a less-desirable AMC model 20 rearend. The front is the Dana model 30. The standard axle ratio was 3.54:1, with an optional 4.09:1. You might get lucky and the gear ratio tag will still be attached to one of the cover bolts for an easy ratio check.

There is a lot more that I could cover about your Jeep, but half the fun of owning a Jeep is slowly discovering more about it and the modifications that can be made to improve its trailability.

Letter Of The Month
Fluid Changes for Better Mileage
Question: For the life of me I do not understand how changing the oil and air filter can improve your gas mileage, particularly the air filter. With vehicles running air mass sensors, the mixture remains controlled by the computer. Air restriction by the air filter would limit horsepower and might actually result in higher mileage, if I am not all wet.
Roger Russ
Ottumwa, IA

Answer: Well, let's look at it in a couple of ways. First off, not all vehicles on the road are fuel-injected. There are quite a few of us who still use carburetors. When the air filter gets restrictive and less air can flow, the air/fuel mixture will become richer. A classic example of an engine running on a rich fuel mixture is when the choke is fully or partly closed.

Something that a lot of people don't understand is that the air/fuel mixture is rated in pounds of fuel and pounds of air used. Gasoline fuel weighs in at about 6.84 pounds per gallon and takes up about 0.13368 cubic feet per gallon. Air weight can change due to density, but you can figure on about 1.2 ounces per cubic foot. You can do the math if you like, but it takes a whole lot of air volume being sucked into an engine to make it run. For instance, my carbureted 383 Chevy engine will suck in something like over 600 cubic feet per minute in the upper rpm range.

The point I am trying to make here is that there is a lot of air flowing through the air cleaner. This applies to a carbureted or fuel-injected engine, and like you say a fuel-injected engine has a MAF (Mass Air Flow Sensor) that sends a signal to the computer that in turn tells the injectors how much fuel to let in. So in theory, the less airflow, the less fuel flow. However, there are other things that come into play, like the percentage of load on the engine and the throttle position. Now with less airflow, the engine will produce less horsepower at a given engine speed. However, the Electronic Control Unit (computer) receives readings from quite a few sensors, such as the coolant temperature sensor, throttle position sensor, oxygen sensor(s), engine speed sensor, and says something like "I am having problems making the amount of horsepower that I need to maintain this given amount of speed. I need to correct this." How does it do this? By increasing the air/fuel mixture to a richer degree, hence more fuel is used.

A dirty air filter can affect the computer's ability to adjust for correct air/fuel ratio. In a mass airflow system, a partially blocked air filter would obviously let less airflow through. The MAF sensor will read less airflow, the computer will adjust the Injector pulse width to gain the optimal A/F ratio. This is called fuel trim. The catch is a computer can only trim to a point. After that the computer is at its limits and performance will go down. The same effects can happen with a vacuum leak after the sensor. A speed density system works about the same way but uses the MAP (manifold absolute pressure) sensor to measure manifold vacuum. A plugged air filter will cause a change in manifold vacuum and again fuel trim can only adjust so far.

It would be nice if I could go into some engineering jargon, and give you a whiz-bang answer, but my shade-tree education just won't produce that, so I gave you the simpler approach that I hope is a sufficient answer.

About changing the oil. I am not sure what you mean this in reference to, but changing the oil can have an effect on fuel mileage. That is one of the reasons that a lot of late-model engines specify 5W-30 oil. It's proven that up to a 5-percent gain in fuel mileage can be gained by using this lighter oil instead of say a 15W-40. It's a fact of physics that a thinner oil will flow easier and faster at a given temperature than a heavier weight oil will. This means that the oil pump will have to do less work and there is less internal friction, or parasitic drag, in an engine.

Oil companies are constantly updating the quality of the oils. However, that does not mean that you can run out, buy some 5W-30, and use it in an '88 Chevy. Late-model engines have much tighter clearances on all moving parts to allow the new style oils. If you tried to use it in a motor that was not so designed, the oil pressure would be quite low and in some cases the engine could be damaged.

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