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  • TDC - Technical Questions & Answers - August 2005

TDC - Technical Questions & Answers - August 2005

Bruce Caldwell
Aug 1, 2005
Cuttin' Class
Q: What's the big deal about cutting coil springs as a quick and easy way to lower a truck? I've read before in your column where you advise against it, yet I know lots of people who have done it and their trucks seem OK. I have an '85 Chevy Scottsdale pickup that I'd like get a lot closer to the ground. I figure later I could get airbags, but right now I just want it slammed.
If a guy is going to cut the coils, what's the best way? Is there a coil spring from another car or truck that I could swap in instead of cutting my coils? I'm open to suggestions as long as they don't cost too much.
Dan Dumond, Cincinnati
A: We, too, know plenty of friends who have successfully lowered their cars and trucks for very little - if any - money by lopping off a coil or two. That doesn't mean it's the right way to do it. We also know people who never wear seatbelts and they're still with us. We still wear seatbelts.
The problem with cutting coils is knowing just how much to remove. People tend to whack them off in single-coil increments. Removing a single coil is generally a pretty benign process. You can't go too wrong or cause too much damage. The general rule of thumb is that removing one coil should drop your truck about 1-1/2 inches.
Few coil-cutters are content to leave well enough alone. They want to go lower, so they cut again. Each time you remove a coil, you seriously alter the design of that spring. The job of a coil spring isn't to just hold a vehicle at a specific static height. The more important roles are keeping the tires on the road, providing a comfortable ride, and supporting the weight carried by the truck.
Things such as the thickness of the coil, the height, and the number of windings affect a coil's behavior. When you remove coils, ride quality suffers. When you're young and more concerned with cool than comfort, that might not be a big deal. And maybe you don't carry big loads in your bed or tow a trailer. If you do, that's a big reason not to cut coils.
It sounds like cost is a major consideration for you. Take a little time to shop the ads in Sport Truck or do some Internet searching. You'll be pleasantly surprised how affordable lowered coil springs are, especially for Chevy trucks. These springs are designed to maintain a decent ride, plus give you the desired drop.
If you do insist on cutting your coils, use a cut-off wheel. Don't use a torch. Torches are super-quick, but they're also inaccurate. The worst thing you can do is just heat coils until they collapse instead of cutting off a coil.
You should have your frontend aligned after lowering the truck. You might be able to find an alignment shop that has experience in cutting coils and would be willing to do both jobs. They're not going to cut things so they have problems with alignment.
You could swap springs if you knew exactly what spring to pick. We know people who have used springs from a six-cylinder car in the same model car with a big-block to lower the car. Maybe someone highly knowledgeable and patient could find a suitable spring swap at a wrecking yard, but we bet you could spend about the same money buying purpose-built lowering springs. In any swap situation, the spring has to fit in terms of diameter and how the ends of the springs fit the spring pockets.
Lights Out
Q: The dome light in the overhead console in my '96 Bronco XLT Eddie Bauer edition is very erratic in its operation. It's usually dark when I go to work, and I carry a lot of stuff with me. It's much nicer to be able to see what I'm doing than to get into a dark cab. I've checked the bulb, twisted it, cleaned the socket, and tried new bulbs, but I'm still having trouble. The idea of testing electrical circuits intimidates me. Is there something else I may have overlooked? I hope you can shed some light on this subject.
M.J. Martczyk, Tampa
A: Chances are good that there's an easy fix for you, as long as your Bronco was built before February 1996. It seems that owners of other '94-'96 Ford Broncos and '93-'96 Explorers have had enough similar problems that Ford developed an overhead console kit to fix the problem. The kit carries part number F67Z-78519C42-AA. Ask about it at your Ford dealer's parts department. They can also help you determine when your truck was built.
Johnny Knoxville
Q: I have a rather noisy '94 Ford Ranger XL pickup. It's a pretty basic truck with the regular cab, short bed, 2.3L four-cylinder engine, five-speed manual transmission, Traction Lok rearend, and air conditioning. The truck has about 135,000 miles on it. I'm not the original owner, but I think all the major components are original.
The noises seem to be coming from both ends of the truck. The noise that most concerns me is the engine knocking when the truck is cold. It is most obvious when I first start the truck, especially on colder mornings. It doesn't seem to burn much oil. I have it changed whenever the local quick lube place runs a sale, so I'm pretty much on a regular schedule. I check the oil once or twice a month.
I tried a couple different brands of oil additive, but it was hard to tell if things were any better. If they were, it wasn't much. I've driven cars that had a connecting rod going out and this noise isn't near that bad, but it still concerns me. Do you think I might have a bad rod?
There is another front-end noise that I can't easily describe. It seems to be more of a squeaking or rattling. I notice it most when I hit a nasty pothole. I checked that my shock absorbers were secure and I checked all the other bolts I could see in the suspension. I have the truck lubed when the oil is changed and I haven't had any unusual tire wear, so I think the suspension is OK. I know I'm being vague, but does this sound like anything to you?
My third noise definitely comes from the rear of the truck. I suspect the rear axle, which is a little odd because the guy I bought the truck from made a big deal about having the rearend rebuilt. That's why I'm sure it has Traction Lok. The noise occurs most often when I make tight turns at relatively high speeds, such as when I'm turning off a freeway or major thoroughfare. I've noticed the noise most when the bed is empty (most of the time) and I have the rear slider window open. I hope you can help me get a quieter truck. Thanks for your consideration.
Johnny Benson, Oak Ridge, Tennessee
A: We have some suggestions that have solved similar problems on other Ford Rangers. The 2.3L engine in your truck has been known to knock due to a defective or badly clogged oil pump. This can be especially noticeable when the engine and oil are cold and not circulating as freely.
There is a Ford service bulletin (#93-20-13) that deals with the problem. It recommends the installation of a new oil pump (PN F3ZZ-6600-A) and a new oil galley rod (PN 391537S102). It's also possible that your oil pump pickup screen my be partially clogged. When you change the oil pump, you'll naturally see and deal with the pickup screen.
Your other front-end rattle could be almost anything that's loose. When you checked the front suspension, did you check body components such as bumper bolts and radiator supports? A problem that's been noticed on other '93-'96 Rangers is loose frame rivets. You'll need to look carefully to find and inspect all the rivets. If you find a bad one, it should be replaced with an appropriate heavy-duty nut and bolt. Bad rivets shouldn't be welded.
The fact that work had been done to the Traction Lok unit suggests that might the recurring source of the problem. A chattering noise on cornering is symptomatic of a Traction Lok with a lack of friction modifier or one that has had the clutch packs over-shimmed. You could try adding a Ford-approved friction modifier. If that doesn't quiet things down, you'll need a rearend specialist.
Gas Pains
Q: How can I improve the fuel economy of my '90 GMC 1-ton crew cab dualie? It currently gets between 10 and 12 miles per gallon. It has a 454ci big-block with throttle body injection and a Turbo 400 transmission. Would a more modern overdrive-type transmission be worth the trouble and cost? How much fuel economy improvement could I expect?
Jason Johnston, via e-mail
Q: How much of a rearend gear ratio change would I need to make a noticeable mileage improvement on my '00 Ford SVT Lightning? I don't want to sacrifice too much performance, but I'd like to save money on today's out-of-control gas prices.
Matt Owens, via e-mail
Q: What are the best fuel economy changes a guy can make to a '98 Silverado for less than $500?
Bob Inglestat, via e-mail
A: We sense a trend here. These few excerpts reflect a sampling of inquiries with a common theme: How can I save fuel without seriously sacrificing my truck's performance? The second part of the common question is: How much will it cost to gain X miles per gallon improvement?
The pivotal equation is improving fuel economy economically. If the changes were free or very inexpensive, they'd already be on your truck. Manufacturers would be thrilled to offer fullsize trucks that could deliver compact-car fuel economy.
But life is full of compromises. The balance of power to fuel economy is a delicate one. Up to a point of diminishing returns, improvements can be made for reasonable outlays. Things such as a high-performance air filter, after-cat performance exhaust system, and modified computer chip or custom tuning offer excellent returns for reasonable investments.
Things such as proper tire inflation pressures, not carrying excess weight, consolidating errands, and conservative driving habits are all free. Proper vehicle maintenance always makes sense. A well-tuned efficient engine returns optimum fuel economy.
We're all for saving fuel and there's something about seeing gas prices jump 5 cents every couple days that grinds us, too. Prices go up far quicker than they drop. Why? Because they can, that's why. It can be as much a psychological hit as a serious financial crisis. Somehow those huge gas price signs serve as a constant reminder of our frustration with big business and big government.
People don't do a lot of economic analysis when they buy a $2,000 set of rims and tires. They just get them 'cause they want them. If you'll feel feel about unpredictable gas prices by making fuel economy upgrades to your truck, do them and don't worry about the return on investment.
If total cost per mile matters, do the math. Say you have a good small-block truck that averages 15 mpg on Regular gas. On the West Coast, as of this writing, $2.50 is high for Regular. Say you drive 15,000 miles a year. That's 1,000 gallons of gas for $2,500. If $1,000 worth of equipment (a new transmission could be more like two grand) yielded a 20 percent improvement, that thousand gallons of gas would be reduced to 833 gallons. At $2.50/gallon, you'd save $417; at $3.00/gallon, you'd save $506; at $4.00/gallon gas, you'd save $668; and if the price of gas doubled (hopefully a worse-case scenario), you'd save $835 per 15,000 miles driven.
At the extreme end of expensive gas, you're still shy of the cost of the fuel economy improvement. If this turns out to be another short-term run-up and prices readjust to something in the $2.50 to $3.00 per gallon, your upgrades would take more than two years to break even.
What we used to consider cheap gas ($1.00, $1.50, $2.00) probably isn't coming back, so making modest fuel economy upgrades makes more sense today than it did during previous price spikes.
Happiness Is A Tight Rearend
Q: I've got an '04 Toyota Tundra that I'd like to lift and install 35-inch tires. My mechanic says that I'll need to install a new set of gears in the rear axle after I lift the truck. I'm unsure of the reason for this. Aren't the stock gears strong enough? I don't want to lift my truck until I'm sure that it will be safe and reliable. What do you say?
Brett O., Roanoke, Virginia
A: There are quite a few good reasons for swapping in a different set of gears for your Toy'. The most obvious is reason is to put the final drive ratio of your truck back to factory specs once you install the new wheels and tires. This is important because Toyota spent a great deal of R&D time to carefully match the powerband of the engine to the transmission and rear differential gearing in relationship to the tire diameter. The factory did so to enable the truck to not only maintain good fuel economy, but also take advantage of the available horsepower when towing or cruising.
By switching from the stock 31-inch-od tires to the much larger 35-inch-od tires, you will be effectively changing the final drive ratio of your truck, which affects several key areas of your truck's performance. First off, the speedometer will not display your actual mph. The larger tires will cover more distance per revolution so the speedo might read that you are moving at 65 mph when actually you might be going 69 or 70 mph. This is bad news if you don't pay attention and a cop catches you flying over the speed limit.
You'll also notice that when cruising down the highway, the engine rpm will drop significantly versus stock and that the transmission may hunt for a lower gear any time you encounter the slightest grade. This condition will put undue stress on the transmission and actually decrease fuel economy even though the engine is turning less rpm at the same speed. You'll likely have to push down harder on the go pedal to maintain the same speed.
Our research indicates that your truck is probably equipped with a 3.90:1 ring-and-pinion gearset from the factory. When you switch to 35-inch tires, we recommend upgrading to a new 4.56:1 gearset and that should put your truck back into its happy zone.
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