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December 2008 4x4 Truck Tech Questions - Tech Line

Hummer H2
Willie Worthy | Writer
Posted December 1, 2008

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Los Angeles, CA 90048.

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New Hummer Six-Speed Clunks
Question: I own a new Hummer with the six-speed automatic transmission. I love the vehicle, but when I am in Drive and start out in First gear and then let up on the gas, there is this clunking noise either just before or just after the transmission shifts. My dealer says that this is normal, but it sure doesn't seem that it should make this kind of a noise.
Jim Alberton
Los Angeles, CA

Answer: Your dealer service manager needs to look at GM Technical Service Bulletin No. 08-07-30-012, which covers this problem with the 6L80 six-speed automatic transmission. There is a revised transmission calibration that requires a reprogram of the Transmission Control Module that should solve your problem.

Using Snow Chains The Right Way
Question: The other day, a couple of my buddies and I were talking about a snow trip we took where we had wished we had chains for our tires. I know that you live in Montana, which gets a lot of snow. My question is: If you only have one set of chains, should they go on the front or the back? Any other tips you have on using chains?
John Phillips

Answer: I am a California transplant to Montana, and in the 17 winters that I have been here, I've only put chains on my vehicles about three times. Where I lived in California, they got put on about 10 times each year. Why? Because driving conditions were a lot different. Montana does an excellent job of keeping the highways clear of snow. Some of the passes do get pretty nasty at times, and chains are then needed.

There have been a lot of tire technology changes in rubber compounds and tread design, which makes a difference in traction in both ice and snow. Besides that, the snow conditions are a bit different, and I only play in it with my vehicles when it's hard and firm, where flotation is the secret; not soft and slushy, where you have to dig through it. But that is really not the answer you're looking for, now is it?

I will give you the same answer that I gave a reader some 20 years ago and which I still find true. I prefer chains on the front tires. They're easier to install on the front because the wheelwell opening is generally bigger, and the wheel itself can be turned for better access to the inside hook if necessary. Putting them on the front also provides better steering and braking control. Most likely, better than 60 to 70 percent of stopping power is from the front wheels. If the front tires slide, steering is lost. You also get improved traction when going uphill as weight transfer causes the front tires to lose traction.

There are also some drawbacks to putting them up front. You will have to use four-wheel drive more often than if the chains were on the rear. On a downhill curve, the back end of the vehicle may want to slide outward and an oversteer condition exists. However, this can easily be corrected by a bit of throttle input and letting the front tires pull you back straight. With chains only on the back, there is a tendency for the front end to "push" (that is, not steering where you want it to go as the rear is doing most of the work).

When it comes to chains, buy the biggest, nastiest ones you can find. I always go oversize and cut the extra length off. I want the crossbars to come way down along the tire's sidewall. Not only do you gain some traction in deep snow, but the chains don't have the tendency to walk off the tire. I also double up on the crossbars. I found that this really makes a difference in traction. Put the chains on as tight as you can get the adjusters, and then drive a bit and retighten. I use heavy-duty commercial tarp tie-downs instead of cheap bungee cords or those silly excuses they sell for chain tensioners.

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