Steering Feels Fuzzy Q: When I drive my 1999 F-250 Super Duty 4x4 diesel pickup (with 87,000 miles) at highway speed, there's a lot of play in the steering wheel. I took it to a mechanic, who replaced all four shocks, the steering stabilizer, and the steering box. The truck has just as much play as it did before. I got underneath it, but couldn't find anything loose. The ball joints appear to be in good shape. What should I do next? My wife won't drive it, because she thinks she'll lose control of the vehicle.
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A: Assuming you've noticed a real problem and aren't just observing the normal handling of a 3/4-ton truck, get a second opinion. Another thorough inspection of the suspension is in order as a safety precaution. Inspect the tires. Are they the right size and rating, in good condition, and holding correct pressure? Then, do a detailed inspection of all suspension parts, including the rear. Something loose in the rear suspension often comes across as a wander in the front. Be sure there's no play in the shaft within the steering column itself. Once the basic possible causes have been eliminated, there are additional items that may have had an effect on your Super Duty's ride and handling. First, confirm the correct wheel-alignment settings, front and rear. It may be correctable with adjustment; also, something significantly bent from impact may now require replacement. After the alignment checks out, another inspection of the ball joints should be performed. There have been problems in the past with binding ball joints that may produce stiff steering, wandering, or poor "returnability." These sealed units are replaced with modified parts that require periodic lubrication. There's a procedure to test the ball joints that calls for the use of a torque wrench at the steering knuckle. Last, verify the correct "steering gear mesh load" at the steering gear (box), this time with the torque wrench applied at the steering wheel after disconnecting the gear from the steering linkage. The new unit may be too loose or tight, causing problems.
Tired Wipers Q: I have a 1996 GMC Sierra, and when I use my intermittent wipers, they sometimes stop in the middle of the windshield for a few seconds. Is this a sign that the wiper motor is starting to go, or could it be something else? My truck has 114,000 miles on it.
A: It's probably not the motor itself, but close. Start with a call to GMC at 800/462-8782. There's a recall in effect, referring to intermittent or completely inoperable wiper motors on a large group of 1994-1997 GM trucks, SUVs, and minivans (Recall #03023). Make sure you have the truck's VIN handy when you make the call. The defect involves cracked solder joints at the controller circuit board, attached to the wiper motor. If your Sierra is on the list of affected vehicles, any GMC service department should replace the circuit board at no charge, with no time or mileage limitations. If your particular pickup isn't on the list, or records show the recall repair was already completed, the problem may lie elsewhere, but the circuit board would still be high on the list of potential causes.
Ford Rearend Chatter Q: I have a 2002 Excursion with the heavy-duty tow package, 7.3-liter diesel, and limited-slip differential. At about 25,000 miles, I heard a chattering noise while accelerating into a turn. It was notably worse with a 2000-pound trailer in tow. I took it in, and the dealer replaced the differential pack. Ten thousand miles later, it started up again. I took it to another dealer, who added a friction modifier to the rearend. It worked its way in and the problem subsided after a few hundred miles. Now at 44,000 miles, it's doing it again, albeit less than before. I went back to the dealer, who was again advised by Ford tech support to add the friction modifier, but mentioned that some chatter is normal in Excursion and Super Duty rearends. I tow about 10 percent of the time and only at about 40 percent of the truck's rated capacity. What's going on here?
A: Every clutch-type limited-slip differential has the potential to chatter on turns. While driving straight ahead, it keeps the two axles locked together to improve traction. The clutches are calibrated to break free and slip at a specified torque and allow the two wheels (or two pairs on a dualie) to rotate at different speeds when making a turn. Occasionally, the lubrication property of the rear-axle fluid breaks down, causing the smooth slip to become a stickier chatter. Each individual rear-axle design is more or less prone to the condition, and your extra-large SUV seems to be at the top of the list. I wouldn't be all that concerned, but here are a couple of items to keep in mind. First, ask the service department to determine exactly which rear axle your Excursion has. The book shows several choices, but most Excursions use the Ford 10.5-inch rear-axle assembly with the Traction-Loc differential. This unit should use nothing but SAE 75W-140 synthetic rear-axle lubricant after the installation of Additive Friction Modifier. Another axle may require a different grade lubricant. Immediately after service, you or the technician should go to a parking lot, cut the steering wheel all the way in one direction, and do about 20 circles, then cut it the other way and do 20 more. This is the best way to work the additive into the differential's clutch material. Ford considers a slight chatter noise on slow turns after extended highway driving an acceptable characteristic with no detrimental effects. If service quiets things down, go through this process when necessary.
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Cadillac Cooling Woes Q: We were thinking about buying another Cadillac Escalade, but we recently had problems with the air-conditioner. The dealer installed another fan to help cool the engine. I saw the directive from Cadillac, and this was the proper fix directed by the manufacturer. The fan was noisy. It sounded like a vacuum cleaner and caused the engine to run rough. We had the fan removed and are now considering a trade for something else. If you can, please let me know if the new Cadillac convertible has the same engine/air-conditioner combination?
A: That's quite a jump from the big, bouncy luxury SUV to the XLR, Cadillac's new two-seater convertible. The Caddy TSB comes right out and tells us that the auxiliary coolant fan "will create a roaring sound when operating." Hey, at least they're not trying to hide anything! The installation of the electric fan in front of the A/C condenser was an attempt to improve air-conditioning performance while idling for extended periods of time. This was to compensate for insufficient airflow produced by the mechanical clutch fan. Sounds like the additional alternator load from the fan motor may have lessened idle quality. The TSB applies to a large number of GM full-size SUVs with the 6.0-liter V-8, but it doesn't seem to be a widespread problem. I took a look at a 2004 model, and GM hasn't included the auxiliary fan in new production. To be safe, do a thorough road test of a new Escalade to ensure good duct temperature in high ambient-temperature and dense traffic conditions before taking the big step. The XLR is an all-new luxury/performance roadster to help GM keep up with the Mercedes-Benz SL500, Lexus SC 430, and Jaguar XK8 competition. You'll see the all-out sports-car version of the new platform with the unveiling of the 2005 Corvette. The XLR uses a high-output 4.6-liter V-8 pushing 320 horsepower, and chances are good that any Escalade air-conditioning shortcomings shouldn't be a factor with this dissimilar vehicle.
Touching Too Much? Q: I have a 2002 two-wheel-drive GMC Sierra HD 2500 with the Duramax diesel and Allison transmission. The yellow rubber bumpstops on the front suspension, mounted outside the frame, are in contact with the lower control arm when the pickup is at rest. It was like this when new, so I assume this is how it was assembled. I looked at an Expedition, and there are several inches of clearance before the bumpstop makes contact. It appears the suspension travel on the GMC pickup is severely limited, since it's already sitting on the rubber stop. Is there something wrong with the setup on my pickup?
A: I wouldn't lose any sleep over it. The similar rubber part on the Ford Expedition is there to cushion the blow of the control arm striking the frame during severe driving conditions where the suspension travel may reach its downward limitations. The Sierra HD bumper is taller and more pliable and just begins to make contact with the control arm while the suspension is at its neutral position. This prevents the control-arm-to-frame contact, while adding an extra cushion during downward suspension travel. I'm not sure why GM engineers felt it was necessary, but it's a normal characteristic of your truck's suspension and shouldn't create a problem. If it were limiting suspension travel, one symptom would be a rock-hard ride.
Chevy Light Reset Q: I replaced the OEM load-leveling shocks on my Chevy Tahoe. How do I turn off the "Service Ride Control" light on the message center?
A: Did you replace the shocks in an attempt to repair the problem, or did the indicator come on after the fact? The Service Ride Control message is activated by an electronic suspension control module, which may control up to three systems. These are the automatic level control (controls rear suspension height via air pressure directed to the newly replaced shocks), real-time damping (adjusts damping at all four shocks), and variable effort steering (controls power-steering pressure). A qualified technician will have to use a scan tool to read and/or erase trouble codes involving any one of the suspension systems. There have been problems with an A/C hose making contact and damaging a connector at the RF shock-damper solenoid. It sets a real-time damping code that requires a new connector and modified hoses to correct. If your problem began after the installation of the new shocks, look for an air-pressure leak or blockage at one of the pressure lines. Also, inspect all electrical connections and anything else you may have gotten your hands on.
GM Throttle Woes Q: I'm having an idle and hot-start issue with my 1999 GMC Sierra with the 5.3-liter V-8. When the engine's cold, it starts up just fine, but if it's hot and the truck sits for more than 10 minutes or so, it will take 5-10 seconds before it'll start. If it sits less than 10 minutes, it starts without difficulty. Also, the engine will occasionally stall as I bring the truck to a stop. It has a rough idle as well. It sometimes lurches forward when stopped with the truck in gear and my foot on the brake pedal, as if it's trying to accelerate. These problems occur more as the air temperature gets hotter. The fuel pump seems to be working. I turn the key to run and can hear it for about two seconds. I have replaced the fuel filter, vapor recovery canister, and the purge solenoid valve.
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A: Hearing the fuel pump buzzing in the fuel tank confirms an attempt at priming the fuel rail with pressure at initial startup, but it doesn't confirm correct pressure (55-62 psi). The inability to maintain pressure prior to startup is a common cause of an extended crank condition. The pump may be tired and not producing. There may be a bleed down of fuel pressure back to the tank, past the pump's internal check valve or the fuel regulator. There may also be one or more fuel injectors that are stuck partially open. This requires diagnosis by a trained technician with a fuel-pressure gauge. Once proper fuel delivery is confirmed, there are a couple of other areas to investigate when dealing with a hard-start or poor idle/stall condition on the 5.3-liter: one is the throttle-body assembly. There's a method to remove carbon buildup and a modification that plugs an air-bypass hole in the throttle plate. The throttle position sensor (TPS) voltage can also be adjusted by means of a minimum air rate screw. The complete throttle-body assembly may require replacement if there's excessive accelerator-pedal effort after carbon removal, or initial TPS voltage is beyond specifications. There have also been cases of the material in the fuel-filler hose, located between the gas cap and the tank, releasing compounds into the fuel system that may cause injectors to stick closed. A modified hose and an injector-cleaning procedure can help. A less common source may be causing your problems, but here's the best place to start.
Shifty Dodge Tranny Q: I own a 1993 Dodge diesel that I bought used in 1996. Within the first year, while towing another vehicle, I noticed the overdrive dropped out intermittently. I paid for a transmission overhaul. The problem turned out to be a device called the throttle position sensor that sends voltage to the PCM (computer), which in turn controls overdrive and shifting. I've had the truck seven years now, and this specific device has been replaced four times. The new TPS corrects the problem, but always goes bad again. In 1992, Dodge issued a corrective measure by replacing the connecting plug, and this is about as much info as I can get from Dodge. The cost for repair is approximately $300.
A: It's tough to determine the cause of a repeat TPS failure off-scene. However, if it happens again, stop by your Dodge dealer and politely ask for a copy of TSB #18-06-93 Rev. A. The problem is erratic fourth-gear engagement (hunting) on the 5.9-liter Cummins diesel with an automatic transmission. Several components may contribute to the condition, including the coolant-temperature sensor, transmission-temperature sensor, vehicle-speed sensor, park/neutral switch, and, of course, the TPS. Double check the electrical connections, and replace the connector and the sensor if there's any sign of water intrusion. Next, take a close look at the injection pump mounting bracket and gear housing. There have been cases of the bolts coming loose, the shifting parts causing unstable TPS voltage. The bolts should be torqued to 18 pound-feet. Also, make sure that you're replacing the TPS with updated part number 4746966. If everything else looks good, and it's confirmed to be another failed sensor, go with an aftermarket part. There's a good chance it may be more durable than the factory unit.
Toyota Clutch Pop Q: I have a 1996 two-wheel-drive Tacoma with a transmission that jumps out of first gear when the clutch is let out from a stop. I purchased the truck new and have had problems with stiff shifting from the start. I assumed it would wear in and shift easier but it never did, and now it jumps out of gear. I occasionally have problems getting the transmission into reverse. Sometimes I have to let the clutch out and then put it back in for the gears to mesh. This particular problem has cropped up in the last 5000 miles. The truck has 115,000 miles on it and runs well.
A: The original stiff-shifting condition and intermittent difficulty going into reverse might have been normal characteristics, but popping out of gear is undoubtedly an internal manual-transmission problem. Some folks might be mistakenly steered toward the clutch assembly. With the mileage at 115K, you may end up doing a swap with a used or rebuilt unit. But if you have the skills, check out one possibility that may be diagnosed and repaired prior to teardown or removal of the transmission: There were a couple of different five-speed units installed on the 1996 Tacoma, but the most common will have three Allen screws on the left/center of the transmission case that may be accessible. Each screw-plug holds in place a spring and ball that sit in grooves on each shift-fork shaft. Without getting too technical, these are what actually apply the pressure and hold the transmission in gear. Jumping out of gear may be caused by deterioration of one of the springs, so it can no longer apply enough pressure. You can remove each screw-plug, one at a time, and extract the spring and ball for inspection with a magnetic probe. If a spring looks like it's falling apart, replace it, and road test the truck to confirm the repair. Keep in mind that each screw-plug may be a different length and also may require sealant before reinstallation. If the springs look good, the transmission will require teardown, and the culprit could be a damaged shift fork, gear, or bearing. Again, at that point you may be better off with a used or rebuilt replacement.
How To Reach AlexIf you have a technical question regarding your pickup, SUV, or van, feel free to contact Alex, a master technician with the National Institute for Automotive Service Excellence. Send a letter to him in care of Truck Trend Garage, 831 S. Douglas Street, El Segundo, CA 90245, or e-mail us at trucktrend@sourceinterlink.com. Please include the VIN with your question. Due to the volume of questions received every month, we cannot guarantee that everyone's question will be personally answered or will appear in the magazine.
Can't wait for help with a problem you're having with your Truck or SUV? Ask the expert we trust here at Truck Trend Garage--visit Alex Steele at www.RealWorldAutomotive.com.
