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April 2010 Nuts & Bolts

Posted in How To on April 1, 2010
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GM Tech Questions Answered
In Jan. '10 we decided to take Nuts & Bolts in a different, temporary direction. We have been gathering up your tech questions and taking them to the people who build new 4x4s. Last month was the Toyota truck guys, and before that Ford and Dodge. This month is GM's turn. Send us your Jeep questions next to

Solid Or Not?
Q For a short time GM offered a solid front axle 4x4 variant of the medium-duty Kodiak trucks (4500/5500). This truck was massive and was the last solid front axle 4x4 to come from GM. Why does GM continue to use independent front suspension in their 3/4- and 1-ton trucks when the competition uses a solid axle?

A General Motors responds: We feel our independent front suspension offers a good balance between capability and ride/handling. Stay tuned for some improvements in upcoming model.

4WOR responds: We still like the simplicity of a solid axle, but are excited to see the improvements you are working on.

Super Silverado?
Q Will the Silverado 1500 ever come with a front locking differential?

A GM: Sorry, we can't discuss future product plan specifics. We do appreciate the feedback and input and will consider all of the feedback we receive when developing future products.

4WOR: Here is some feedback. Build a 2500 Duramax truck with front and rear locking differentials, long-travel suspension, and 35-inch tires. Include an airbag-over-leaf-spring rear suspension so it can haul a heavy load while still being able to go fast in the desert or mud hole. Maybe add a heavy-duty bed that can take trail abuse and still haul gear. Call it the Silverado Super! We did a design drawing for you so you can get started on it.

Not Gone Yet
Q Everyone knows there were diesel engines in the works for OEM half-ton trucks. These seemed to have stalled. What is needed to get these back on track and into production?

A GM: As we announced, this powertrain was shelved, not canceled. We continue to monitor the marketplace as it relates to this and other issues.

4WOR: Excellent! Put this in the new Super Silverado 1500!

Secret Silverado
Q With the immanent sale of Hummer to the Chinese, GM is losing its most capable 4x4. And now with Ford's new Raptor truck, the return of Dodge's Power Wagon, the Jeep Rubicon, and both Toyota's and Nissan's capable SUVs, it seems GM is missing out on the off-road market while every other manufacturer is staking a claim. What is GM's view of the off-road market at this time, and are there any plans, insights, or hints of a future 4x4 with front and rear lockers, a low-geared transfer case, winch, and aggressive tires?

A GM: We take the off-road market very seriously. Our Silverado Z71 offers outstanding off-road capabilities. The Silverado ZR2, shown at SEMA this year, was a vision truck of some of our capabilities in the off-road realm. We will definitely look at potentially taking certain elements of that truck and other ideas to implement in future products.

4WOR: Hmm, we like the looks of the Silverado ZR2 and may need to borrow it for a weekend.

NO Man Plan
Q Does GM offer any 4x4 vehicles with a manual transmission?

A GM: No. The manual transmissions had a very low take rate in fullsize trucks, and a decision was made to drop that option moving forward.

4WOR: That's too bad, but even if some folks like them we can't imagine you'd offer them if it wasn't profitable.

Tonneau Testing
Q In your research does a Chevy Avalanche get better mileage with the bed tonneau cover installed or not? This will help me decide to purchase a tonneau cover for my Silverado.

A GM: Generally speaking a tonneau cover provides better aerodynamics and better fuel economy.

4WOR: What if you cut out all the IFS, put in a solid axle and some 39-inch tires, removed the doors, and painted it all flat black? Will it still get good mileage?

Q At the magazine we are constantly looking to help as many readers as possible with our projects and tech articles. What model and engine is the most commonly purchased in a GM 4x4?
A GM: The most popular model/engine is the Chevrolet Silverado LT with the 5.3L V-8.

General Gas Sippers
Q What is GM's most fuel-efficient 4x4 (with a low-range transfer case)?
A GM: At 21 mpg on the highway, the Chevy Silverado or GMC Sierra 4WD truck with the 5.3L V-8 engine delivering 315 hp will give you better fuel economy than anyone in a 4WD pickup. Period.

4WOR: You must be talking about fullsize pickups, because your own Colorado 4x4 with the 2.9L four-cylinder and five-speed manual can get up to 18 city and 24 highway! Not bad for a fun little daily driver/weekend wheeler.

Thanks, GM, for answering our questions.

Submission Information
Confused? Email your questions about trucks, 4x4s, and off-roading tech using "Nuts, I'm confused" as the subject and include a picture (if it's applicable). Digital photos must measure no less than 1600 x 1200 pixels (or two megapixels) and be saved as a TIFF, an EPS, or a maximum-quality JPEG file. Also, I'll be checking the forums on our website (, and if I see a question that I think more of you might want to have answered, I'll print that as well. Otherwise drop it old-school style with the envelope addressed to the address below. Letters published in this magazine reflect the opinions of the writers, and we reserve the right to edit letters for clarity, brevity, or other purposes. Write to: Nuts & Bolts, 4-Wheel & Off-Road, 831 S. Douglas St., El Segundo, CA 90245, fax 310.531.9368. Email to:

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