Q I'm having a problem with the automatic transmission in my '01 Lexus ES with 125,000 miles on it. The reverse gear hesitates when I shift into reverse, catches, hesitates again, then catches and moves the car. The problem is not present when the engine is cold but appears after warm-up. It hasn't gotten worse over the last year but is especially bad when backing up an incline. A transmission mechanic suggested I use reverse gently but it would likely need a rebuild. I did have the transmission serviced several months before the problem started. Any thoughts?

A Was the transmission fluid and filter changed at a dealership or independent shop? Toyota specifies a specific transmission fluid, ATF Type T-IV, for this vehicle. This fluid is not the same as Dexron III, perhaps the most commonly used automatic transmission fluid (ATF). It is quite possible that the symptoms of delayed engagement and slippage are the result of using incorrect fluid. If the wrong ATF was used, I'd suggest a complete flush and refill with the proper ATF T-IV fluid and, if the issue continues, adding 1/2 can of SeaFoam Trans Tune to the fluid -- before deciding on a rebuild.

Q I own a 2003 Buick LeSabre with 75,100 miles on it. We recently took a road trip from Minneapolis to Maine. When traveling at 65 to 75 miles per hour using cruise control, if I needed to slow down or stop for road construction, the transmission downshifted smoothly, but when I increased the speed back to 65 to 75 mph the upshift would result in a "clunk" at each shift. After stopping for a break and starting to travel again, the upshifts would be normal. Also, around town there is no problem. Does heat play a role?

A Very possibly. If the transmission is overheating at highway speed, shift qualify will be affected. Make sure the radiator and grille opening are clear of debris that could cause higher transmission operating temperatures. My ALLDATA automotive database pulled up several GM bulletins addressing concerns with the transmission valve body. Have a scan tool check for any DTC fault codes that could related to the issue. If none are found, and the transmission has never been serviced, it might well be worth a full transmission flush and refill. This would also be the time to inspect the valve body if it is suspect.

Q A friend just picked up a 1996 Dodge Ram Van 2500 with the 5.2-liter V8 and only 48,000 miles on the clock. He got it back to Minnesota and is wondering about improving traction in the snow. Are there any limited-slip rear-end options for this vehicle? If so, where would be the best and most cost-effective places for us to source one?

A Adding or swapping to a limited-slip differential can be a costly upgrade, particularly for a 17-year-old truck. This van could have one of three rear axle setups -- Chrysler 8 3/8-inch or 9¼-inch, or a Dana 60 9¾-inch differential. Considering that new Trac-Lok carriers for the Dana unit start at around $500 plus installation, I'd start shopping the automotive salvage and recycling yards.


Betsy Glennon writes, "I suggest that the writer with the 2009 Chevy Cobalt check to be sure the inflation pressure in the spare with the sensor is adequate. If riding with one in the vehicle, the warning may be detecting low pressure in the spare. This happened in my daughter's Toyota RAV -- all pressures in the four on the road were adequate, but the spare in back was low."

Betsy's note raises a good point. If your vehicle is equipped with a tire pressure sensor in the spare tire, low pressure in the spare can trigger the warning light on the dash. But not all vehicles are equipped with tire pressure monitors in the spare tire, including this Cobalt. If the vehicle is equipped with a full-sized spare, it may well have a tire pressure sensor.