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November 2008 4x4 Truck Tech Questions - Tech Line

Posted in How To: Tech Qa on November 1, 2008
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Where To Write
Address your correspondence to:
Techline Four Wheeler
6420 Wilshire Blvd.
Los Angeles, CA 90048.

All letters become the property of Four Wheeler, and we reserve the right to edit them for length, accuracy, and clarity. The editorial department also can be reached through the Web site at www.four Due to the volume of mail, electronic and otherwise, we cannot respond to every reader, but we do read everything.

Lift Or Leveling For HD Ram?
Question: I have an '00 Dodge Ram 2500 diesel and I am planning some upgrades on the suspension system. I do not intend to lift the truck more than necessary for proper wheel travel. When I read Four Wheeler's article about the Baja Bomber, I thought that was it. Here is the perfect system for me. But after contacting KORE Racing and getting the price, I decided to rethink the project: $6,000 U.S. is a bit on the high side, especially considering that the price almost doubles for the import to Iceland.

Therefore I am wondering if you could guide me in the right direction by doing it a bit cheaper. What I am mainly thinking of is to improve the suspension in the prerunner direction. I am not going to race the truck, but I would like to be able to keep a good speed on the rough tracks. Furthermore, I also travel with a slide-in camper now and then, and am thinking about using airbags to compensate for the extra weight. I am used to doing all the work on my trucks, and I am able to build most things myself.
Stefan Gunnarsson
Hafnarfjordur, Iceland

Answer: Having a slide-in camper changes the whole picture of things when it comes to a suspension lift for your truck. I assume that it is a large camper if you are considering using airbags to handle the extra weight. My suggestion is that you go to one of the "leveling kits" that most aftermarket suspension companies offer. This is nothing more than a large thick spacer that fits between the top of the coil spring and the spring tower. I think that these come in about a 2-inch (or so) lift. Now your truck will sit level when empty and not have that tail-high attitude. However, when you put the camper on, the headlights will be looking for owls and the tail end will be down.

The airbags would be a great solution to both level out the truck and to gain a bit of lift. I would suggest a quality set of shock absorbers to handle the higher center of gravity when the camper is on. We used this combination back in '96 and '97 on our Dodge Project Rammit and it worked out quite well, and yes it carried a cabover camper.

Causes Of Tahoe Driveline Noise
Question: My '03 4x4 Tahoe has a whoomp-whoomp sound in the front drivetrain. It sounds like a helicopter rotor when stopping at low speed to accelerating from a low speed. It's either the four-wheel-drive hub on one side or the 4x4 transfer case in the middle.
Oak Harbor, WA

Answer: Noises like this are hard to diagnose through the mail, but I am pretty sure I have an answer to this one. This noise may be caused by a low clearance condition within the differential in the front axle assembly. In 2WD mode, the front differential has a large amount of relative motion between the differential pinion and side gears. In the 4WD or Auto 4WD modes, the transfer case turns the front propeller shaft, and the relative motion between the differential gears is reduced or eliminated, so the noise is eliminated. The solution is to have your dealer replace the front differential case with PN 26018131. In case the service manager questions you on this, have him look at Technical Service Bulletin Number 03-04-19-004B, dated December 12, 2005, that covers this problem.

Newer GM Engine Into Older GM Truck
Question: I am rebuilding an '84 GMC 1/2-ton fullsize 4x4 pickup with a standard transmission that had caught on fire at one point with a prior owner. I have a donor pickup: a 2WD '91 GMC Sierra C-1500 automatic that has fuel injection. Is it at all possible for this engine to swap over to my '84 GMC? And what are some of the same parts that I can take off the '91 that will fit the '84?
Clint Kartchner
Mule Creek, NM

Answer: Sure, it's possible to make the engine swap, but you had better be an expert at wiring, as that is where the work is. You can use the standard transmission along with a new computer designed for a standard trans or the automatic trans with an adapter from, say, Advance Adapters. I suggest that you contact Painless Wiring for a new replacement wiring harness.

What else you can use off the truck? That depends on what you are swapping. Some stuff may take just some simple adapting, while others may not be worth the effort.

Wants More Power From 5.4L Ford V-8
Question: I am looking at some ways to improve the performance of my '07 Ford F-150. While the performance with the 5.4L engine is adequate, I would really like a bit more power, especially for towing. I was thinking of going with some larger tires and a lift, but I am sure that would hurt performance even more. I am not opposed to spending money on this truck as it is my only play toy. What would you suggest?
Mike Simpson
Los Angeles, CA

Answer: Well, the standard modifications such as headers, after-cat exhaust, and a free-flowing air filter all help. The real way to make a performance increase is with a supercharger. Roush Performance Products (800/597-6874,, offers a great supercharger that will actually not void your new truck warranty. It will give you an extra 112 hp and 112 lb-ft of torque with 6 pounds of boost. The only fault with the system is that you will have to use premium fuel. My guess is that if you can learn to keep from using all the extra ponies, you just may increase the fuel mileage enough to make up for the higher-priced fuel.

If you do go with the larger-diameter tires, you should really consider changing the front and rear axle ratios to a somewhat lower gearing. The larger-diameter tires will increase the overall gear ratio, meaning that the engine will now be at a lower rpm for a given vehicle speed. Generally speaking, the lower the rpm, the lower the horsepower and torque output, so with the larger tires you will notice a lack of power, especially when towing. You might even want to consider setting the ratio a bit lower than what would be necessary to obtain the same engine speed that you had before the larger tires were installed. The lower gearing will definitely help on the towing and perhaps won't really affect the fuel mileage.

Jeep 2.8L Swap Options Debate
Question: I was just reading "Cherokee 2.8L Swap Options" (Techline, July '08), and while you guys have a great magazine, I have to admit I was little disappointed in your response. I do not believe there are any computer or wiring harness issues. It is a carbureted motor. There are also no "front-end" issues as the sheetmetal is the same into the '90s era, regardless of whether it is from the 2.8L or 4.0L generations.

Most importantly, you overlooked a very viable and reliable swap. Since the 2.8L is actually a GM engine, GM Performance Parts offers a crate engine that is an emissions-legal swap for trucks originally equipped with the 2.8L V-6. It is the HT 3.4L, reasonably priced, and it comes with a factory warranty. I personally know someone who performed this swap, and he was very satisfied with the increase in torque. Based on the reader's intended use, this could meet his expectations.

Starting with this as a base, and adding Edelbrock's intake system combined with an upgraded exhaust, you could approach the power range of a 4.0L with a much smaller investment and effort than a 4.0L. Plus you would have the benefit of a factory warranty.

Further upgrades could include a transmission and transfer-case swap from a 2.8L-equipped Chevy S-10 or GM S-15 vehicle from the mid-'80s. This would provide a noticeably lower First gear for off-road use along with an Overdrive gear for highway use. Combine this with 32s and 4.10:1 or 4.56:1 gears, and you could have a great dual-purpose vehicle from the Cherokee that would also provide acceptable fuel mileage.
Rob Karlin
Mesquite, TX

Answer: Thanks for your letter. I like to hear from readers and their opinions.

First off, you have to transfer the wiring harness and the computer from the 4.0 engine even if (more so) the 2.8 was carbureted. And yes, there is a difference between the V-6 and the inline-six in the front bulkhead area where the radiator mounts, so that also would have to be changed.

I am well aware of the fact that it is a GM motor and that GM makes a 3.4L version in a crate engine (or did, the last time I checked into it). In fact, in past editions of "Techline" I have gone into greater detail on this engine. As to the 3.4L being factory emissions-legal, that is debatable, as the Jeep never came with that particular engine. So even though the engine is emissions-legal in a GM vehicle of the same year, it may or may not be so in a Jeep. Lots of gray area here as to what the inspection station has to say about it.

Edelbrock does indeed make an intake manifold and an exhaust system that will work. As to making the same or near the same power with less investment than one would have with the 4.0 motor-I doubt it. And don't count on factory warranties. I just happen to own a GM Performance crate engine that is in my Jeep, and it had a warranty problem that GM would not honor. (See "Willie's Workbench" this month for details.)

As to better gearing with the manual transmission ratios, as I remember, the S-10s were about the same as the Jeeps. Plus the 2.8/3.4 engine block pattern is different from that of the rest of the GM lineup, which limits the transmission choices somewhat.

The 4.3L GM V-6 is an excellent engine, and the four-speed automatic is a time-proven transmission. The fuel mileage of the 4.3, as well as the power output, far exceeds that of the 3.4 motor and makes for a very simple swap, as far as modern emissions-legal swaps go.

So with no disrespect, I will stand by my original answer of either making the 4.3 swap or selling the Jeep and buying another Jeep with the excellent 4.0 motor factory installed.

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