Question: I have a 2001 Chevrolet Silverado 5.3 automatic four-wheel drive Z71, approximately 230,000 kilometres, perfect maintenance so far.
We had some winter weather, and I have some land, and I put my truck in four-wheel drive high, probably the fourth or fifth time ever I鈥檝e had it in four-wheel drive. I parked it and went inside and forgot that it was in four-wheel drive high the next morning. I jumped in my truck and drove approximately 13 kilometres, at the most 120 km/h. I noticed a little bit of tension when I was turning the steering wheel but just blew it off as being cold outside.
I was at the store turning left and noticed the resistance and then I saw the button on the dash 鈥� it was in four-wheel drive high! I immediately I put it in two-wheel drive high and went on. What are my concerns? Could I have damaged the transfer case or the front axle and the CV axles up front? What should my concerns be? It runs fine and does OK now.
J.D.
Answer: Don鈥檛 sweat this! Your time driving on pavement in 4x4 mode was short enough there should be no problems. Your truck is a true 4x4, as opposed to the many all-wheel-drive vehicles out there that power all four wheels at all times but are fussy about having exactly identical tire size/wear to avoid driveline wear.
Operating in 4x4 mode on dry pavement does considerably stress driveline components as well as tear up the tires. As the truck turns corners or makes any turns at all, each wheel needs to turn at a slightly different speed. When four high or four low are selected, the front and rear axles are locked together. The stiffness and wrap-up you detected is fortunately mitigated a bit by tire slip. This is a situation that should definitely be avoided, to avoid rapidly accelerated wear on a bunch of components, but you caught it quickly!
Q: My 2002 Chevrolet truck makes an occasional jerking feeling when I鈥檓 driving about 100 kilometres per hour, and not at any other speed. I feel it when I鈥檓 just pressing a little extra on the gas, as when climbing a slight hill. There is no engine light, and it starts and runs fine at all other times. Do you have any ideas for me to check? Thank you!
M.S.
A: This is a longshot without being there to observe and test. I鈥檓 thinking perhaps engine misfire, and since it鈥檚 so infrequent, that鈥檚 why your OBD-II (on-board diagnostic system 2) hasn鈥檛 yet identified it as an emissions concern and turned on the check engine light. If you can get your hands on a scan tool that indicates cylinder misfire information (either a premium level generic OBD-II scan tool such as the Blue Driver) or a professional grade scan tool, misfire counts can be observed.
Each cylinder is listed, and should one indicate misfires are occurring, I鈥檇 try swapping that ignition coil with a neighbouring cylinder and driving the truck again under the same conditions. If the misfire moves 鈥� follows the coil 鈥� that鈥檚 a slam dunk that the coil is at fault (leaky coils are fairly common). If the misfire remains, swap or replace the spark plug and repeat the drive. If the misfire remains in that cylinder, professional skills will be needed to take the diagnosis further.
Q: Does it weaken the car鈥檚 battery if the headlight (not daytime running light) switch is in the 鈥渙n鈥� position when the car is started? Someone I know leaves the headlights on when shutting off the engine, so that they don鈥檛 forget to turn them on next time they start up. Seems to me this is a needless drain on the battery.
E.P.
A: The battery remains unaffected if the lights switch is left on. When the key is turned (or the engine start/stop button is pushed), the headlight circuit is temporarily bypassed. This is designed to provide maximum battery power to the starter 鈥� very important in freezing weather.
Brad Bergholdt is an automotive technology instructor at Evergreen Valley College in San Jose, California. Readers can email him at [email protected]; he cannot make personal replies.e
