Q. I have a 2003 Infiniti FX35 with just about 100,000 miles. I have never changed the transmission fluid. I have heard that at some point it is not a good idea to change the fluid, but I don’t know if this is true. I’m not experiencing any problems yet. The dealer wants over $200 to change it. That seems like a lot of money just to empty and refill fluid. What are your thoughts on this?

A. This falls into the category of it couldn’t hurt but may be an unnecessary expense. Infiniti doesn’t have a specific interval to change the transmission fluid. Every 15,000 miles the fluid should be checked. If the fluid is in good condition and the transmission is shifting normally, I see no need to service it.

Q. The one-year warranty on the rebuilt transmission/transaxle in my 2002 Toyota Rav4 is about to expire. In very cold weather, it does not shift into 4th gear (overdrive?) for the first mile or so, and then shifts smoothly. It runs fine in warmer weather. The shop said this is to be expected. Is this so? Will it get worse over time?  The transmission failed due to a faulty computer.

A. This is a normal characteristic of this vehicle. Toyota limits shifting into overdrive when the engine coolant is below 140 degrees.

Q. My 2002 Grand Marquis GS suddenly lost electrical power and would not turn on. I tried jumping and it starts, but as soon as I hit the brakes or turn on the lights, the car shuts off and loses all electrical power. The alternator and battery were replaced six months ago. The alternator was checked and found to be OK. Any suggestions on what this could be?

A. The problem sounds related to the battery and charging system. The battery needs to be fully charged and the charging system rechecked. If the alternator was removed from the car and “bench” tested and found to be OK, look for a wiring or fusible link problem that is affecting the electrical system.

Q. I saw on the website that you have a list of engines that will become damaged if the timing belt breaks. I have two older vehicles that I’d like to inquire about: a V-6 engine in a 1989 Toyota SR5 pickup and a V-6 engine in a 2000 Toyota PreRunner.

A. Your two Toyota trucks use very different engine designs. The 1989 Toyota uses a 3.0-liter engine with a rubber timing belt. If the belt breaks on this model, there shouldn’t be any engine damage. In fact, the manufacturer does not have a specific interval to change the timing belt. If the belt has never been changed on this model, my suggestion is to replace it as a preventive measure to avoid a breakdown. The newer truck uses a 2.7-liter V-6 engine with timing chains and for all practical purposes doesn’t require maintenance.

Q. I still try to work on my own vehicles. One of my cars, a 1999 Buick Century, has only 85,000 miles on the original rear brakes. I jacked up the car and tried to remove the drums, but they were rusted in place. I took the car to a garage, and they charged $20 to check the brakes. To remove the drums, they simply hit them with a big hammer. Once the drums were off, the brake shoes appeared fine. They cleaned up the shoes, adjusted the brakes, and all was fine—I thought! Now when I step on the brakes, I get a bit of a vibration. The garage said the brakes just need to wear in. What do you think and is the garage to blame for the new problem?

A. Hitting the brake drums “with a big hammer” distorted the drums. It is possible the drums can be resurfaced and all will be fine. The brakes won’t “wear” in. Was the shop at fault? It may be that the brake drums were so rusted to the hubs that this was the only way to remove them.