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January 2012 Techline - Tech Questions Answered

Posted in How To: Tech Qa on January 1, 2012
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Bolt-in Engine Swap?
I have a ’98 Jeep Wrangler TJ with the 2.5L and I am curious about what V-6s would be an option that would bolt in without any other changes?
Ronny Suggs
Rogers, AR

There is no such thing as a “bolt in motor swap” for your TJ. Most likely the easiest V-6 to install would be the Chevy 4.3 V-6. Your present transmission, an Aisin-Warner AX-5, I feel is not up to any additional power and is marginal at best for any hardcore four-wheeling. However, there must be a limited market for such usage as Advance Adapters ( offers an adaptor. However, the company also makes a kit to adapt the much stronger AX-15 transmission (it is normally found behind the 4.0L six-cylinder) to the four-cylinder engine. If you are unfortunate enough to have an auto tranny, the transmission is labeled a 30RH, which is a version of the Chrysler TorqueFlite 999; however, I am pretty sure no adapters exist for it nor would you want to use it.

A transmission swap is definitely in order along with an adapter from it to the transfer case. You will also need new motor mounts, radiator, wiring harness to match the engine you pick, and most likely modifications to the driveshafts. Wish I had better news for you, but that is what is involved.

Subaru Steering?
Please don’t laugh as I have been a reader of Four Wheeler for a lot of years but my ’02 Subaru Outback has a strange noise. It is a low-pitched groan that appears to be coming from the engine compartment whenever I turn the steering wheel at slow speeds. The mechanic I took it to wants to replace the power steering pump, which is quite expensive; however, it doesn’t seem to make any noise when the wheels are not being turned. Before I have it replaced I thought I would check with the experts.
Larry Simonton

It’s normal for a power steering pump to make some noise as pressure builds when the steering wheel is turned. It may or may not be the pump that is failing but it sure could be. It is quite common for the ’00-’02 Legacy and the Outback with the 2.5L motor to sound like a dying horse when turning. It is probably making the noise when you’re driving down the highway but you most likely can’t hear it over the engine, tire, and wind noise. The simple fix is to just remove the bolt and clamp that hold the two hoses together. I am not really sure why this noise exists and what removing the clamp has to do with it but I have been told that it works and that is what is important.

Now if that doesn’t solve the problem, then I suggest replacing the high-pressure hose with a new-style updated hose under P/N 34610AE09B. Any good parts store can cross over this number to an in-stock brand. Oh and leave the clamp off. If the noise is still there, then your mechanic was right and the pump likely needs to be replaced.

Cool Cold
Here is a tech question for you about auto trans coolers. Can you get the tranny too cold? Specifically, if I were to put a normal tube/fin cooler on an auto-equipped vehicle, do I need to worry about it in the winter months? The more expensive stacked-plate coolers (like B&M) apparently have a bypass valve that works based on viscosity, which is obviously directly related to temperature. So the question is, are the cheaper coolers a good idea for mixed climates like we have in Washington?
Toby Wilcox
West Richland, WA

Yes, a transmission cooler can get too cold. Lubes like to operate in a given temperature range for best wear quality control, be it gear lube, engine oil, or transmission fluid. I have been told by transmission builders that the temperature measured within the oil pan should be 100 to 170 degrees. Yes, synthetic fluid can operate at a wider range than that, but can some of the plastic parts as well as others handle the higher temps? A 170-degree oil temp may not sound very hot, but keep in mind the real temperature is in the torque converter, especially under a heavy load with slippage. It is really easy for temperatures to exceed 250 degrees for a short time. Keeping the temperature within this range allows for sudden spikes in temperature that can be easily absorbed.

I feel that stacked-plate coolers are much better at extracting heat than the tube-and-fin type. However, they have to be as close to the radiator as possible. This is because they have quite a bit of resistance to air flowing through them and the air will have a tendency to just flow around, and not through, the plates. Yes, some of the coolers offered by B&M do have the system you mentioned to control excessive fluid cooling when cold. As to the tube-and-fin coolers, keep in mind that only the boundary layer of fluid that is right against the tubing is what gets cooled. The exception is the coolers that have turbulators within the tubes, such as those pioneered by Perma-Cool ( The turbulators cause the fluid to spin as it is pushed through the tube exposing much more fluid to the tube’s walls where the heat is dissipated.

Wide ranges of temp changes definitely are a problem in the Northwest. Another way would be to put in a bypass valve of some kind that thermostatically directs the fluid path. However, I am not sure it is necessary. You have a couple of choices: run the fluid first through the auxiliary cooler then through the cooler built into the radiator tank. That way you cool the fluid, and then possibly bring it back up a few degrees after it exits the radiator. Yes, the fluid will be somewhat cooler than radiator temperature; however, I can’t really explain why. One would think that it would be close to the same temp as the coolant in the radiator but it is always is considerably lower. Another way would be to go through the radiator first then through the auxiliary cooler. This way you get the best possible cooling effect.

If you think that the temperature is too cool during the winter, one could simply place something in front of the auxiliary cooler to stop the airflow. That is my game plan for the new flatfender Jeep I built. In fact I made sure that my return line comes out the top of the cooler to prevent the fluid from draining back to the transmission when the engine is shut off, as the auxiliary cooler is mounted at the upper section of the radiator. This is just the opposite of common practice but it has worked for me in the past.

Oh, and a tip from one with a past experience, after a few heat cycles go back and tighten all of the hose clamps and fittings. You can’t believe what a mess a couple of quarts of ATF can do when a hose comes loose and, well, ATF hits the fan.

The bottom line is pull the transmission oil pan, braze in a bung and install a transmission temperature gauge in a location where it won’t touch any of the internal components. Even better would be to buy one of the aluminum pans with fins on the bottom and a fitting already in it. Not only are they of much heavier construction, which may or may not be able to take a rock hit without damage, but they offer better cooling potential and typically hold an additional two quarts of fluid. With a gauge you will know for sure what is happening temperature-wise. Shoot for no more than 150-170 degrees.

Exhausting F-Series
I recently bought a ’76 F-250 4x4 with a 390 out of a muscle car (it has relatively high compression and a hot cam). The exhaust system is pretty rusty and I plan on replacing it. What about purchasing headers versus using the stock iron manifolds? I’ve talked to several people about headers, and have heard of problems with them leaking and constantly having to replace the gaskets. If I buy a set of headers, will they have problems with leaking and/or their durability when four wheeling? If I do choose the headers, would a dual three-inch exhaust system be too big for the engine?
Name Withheld

Headers are a benefit to any engine, especially one with high compression and a camshaft change. Every off-road vehicle I have ever owned has had headers and so have most of my street drivers. However, like anything, you get what you pay for. When it comes to headers, price is pretty much what determines the quality of the product, as defined by thicker flanges, heavier wall tubing, and quality welds. The thick flanges will ensure that they maintain a flat contact area with the cylinder head, which in turn helps to ensure that the gaskets don’t leak.

After the headers are installed, you will have to go back several times and retighten the bolts. The heat cycles will cause the bolts to loosen up as the gasket slightly compresses. It’s not a bad idea to just double check their tightness every time you change the oil as part of your maintenance program.

While I have successfully used the fiber gaskets over the years, there are some soft copper gaskets available from Summit Racing ( that are said to hold up better. If you’re really worried about the bolts coming loose, Stage 8 Locking Fasteners ( has some special bolts that have a locking tab that prevents the bolt from turning once installed, but can be easily removed.

Generally speaking, the paint used by most header manufacturers is more of a protective coating intended to keep them from rusting while in storage than it is a long term coating. On mild steel headers I bead blast them, wipe them down with lacquer thinner and then paint them with VHT ( FlameProof Coating. I have tried other high-temperature paints but have found VHT to be the best brand. Some headers can be had with a special coating such as Jet Hot ( that offers superior protection to paint. The best (and most expensive), however, is to go with stainless steel, as there is no need to paint or plate and they last almost forever.

As for the tailpipes to complete the rest of the exhaust system, 3 inches is overkill, and besides being hard to route, will be expensive. A 2½-inch dual exhaust system with smooth, wrinkle-free bends should be more than adequate when combined with some quality mufflers.

Diesel Engine Stoppers
Exactly how does an exhaust brake work? I understand the theory, but also know that if you stuff a potato in the exhaust pipe the engine will stall. Also, are Jake Brakes and exhaust brakes synonymous?
Tiido and Anni Tennelo

No, Jake Brakes ( and exhaust brakes are not the same thing. Let’s go over the Jacobs, or Jake Brake, first. A Jake Brake modifies the timing on the exhaust valves so that, when braking is desired, the exhaust valves open slightly right as the piston reaches the top of the compression stroke, or near top dead center (where ignition normally occurs in a gas motor). When on the upstroke, the piston compresses the air in the cylinder to 1⁄18 its original volume, assuming the compression ratio is 18:1. This creates a lot of drag on the engine. The Jake Brake then releases the compressed air, and the energy stored in it, before it can push back on the piston during the downstroke. In addition, releasing the compression prevents any fuel in the cylinder from igniting. Remember, diesels don’t have spark plugs, they rely on the heat from compression alone to ignite the fuel (except during cold starting when glow plugs are utilized). So, you’ve got drag on the upstroke and no power on the downstroke.

A man by the name Clessie Cummins (Yes, the same one who developed the engine) developed the compression-release engine brake in 1954 and sold the idea to the Jacobs Manufacturing Company, which started production of it. It soon became part of trucking lore.

There are styles of Jake Brakes that are quiet. There are also other companies that make compression-release engine brakes, not just Jacobs. Jake Brake gets a bad rap because the name not only seems to have become generic to exhaust engine brakes, but also has become a sort of icon. The noise is caused by the escaping air and it is possible to muffle it to become almost inaudible, but for some reason some truckers seem to like the noise, even if the public doesn’t.

The exhaust brake, meanwhile, is nothing more than a butterfly valve in the exhaust system. When activated, this valve restricts the exhaust gas flow and increase back-pressure in the engine. There are several ways to control the valve, and different manufacturers have used electronically controlled solenoids, electric motors, air cylinders, and even vacuum motors driven by a vacuum pump. When the exhaust pressure exceeds a set amount, the valve is designed to open, thus preventing damage to the engine or that part of the exhaust system in front of the valve. Yes, if the valve stayed completely closed for any length of time, I suppose the engine would stall out. However, there is some leakage, and some systems even have a separate bypass valve.

The biggest advantage is excellent compression braking on downgrades under heavy loads. I have one made by B-D Power ( on my own Chevy Duramax diesel 3500 truck and very seldom do I have to use my brakes on even the steepest downhill grade, even with a load that may exceed the truck’s maximum CGVW. Having owned an exhaust brake, I doubt that I would ever be without one. Another benefit is faster cold weather warm-ups.

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