Expert Advice

GM Brake Fixes
Q: I have a 2004 Chevy Silverado 1500 4x4 with antilock brakes. The brake pedal is mushy and sometimes goes to the floor without any brake response at all. I've been to the Chevy dealer twice and, of course, the brakes didn't act up either time. I called Chevrolet customer service and had a three-way conversation with it and the Chevy dealer's service manager. They said I was paranoid and couldn't do anything about the brake problem. I read in Truck Trend that 2005 models went back to rear drum brakes and bigger discs in front. Was this change related to a brake problem? Have you heard of any fix for it, such as one for the master cylinder or antilock unit? My truck has 18,500 miles on it, and I'm willing to fix this problem myself to be on the safe side. I've been on the Internet and talked to others who have the same issue and have turned in a complaint to NHTSA, which has recorded accidents from this problem.

A: NHTSA has received similar complaints on Chevy trucks, but apparently not enough to warrant an investigation. There's currently a recall in effect for 2004 models involving the Hydro-Boost power-brake system on the 2500 and 3500 series trucks (1500 uses a vacuum booster) and also a Technical Service Bulletin dealing with unwanted low-speed antilock brake operation, but no documentation pertaining to an intermittent hydraulic failure. GM states that cost and material factors contributed to the brake changes to the 2005 Silverado--nothing about performance upgrading. Communication may be an issue. In the shop, "my brakes went to the floor" is a common phrase. Sometimes, it's an accurate description of a major hydraulic failure that caused a sudden drop at the brake pedal and a complete loss of front or rear brakes. Other times, it's incorrect terminology attempting to describe brake fade, a low or spongy pedal, normal ABS operation, etc. You may want to try another Chevrolet service department, and perhaps speak directly to the technician involved. They may be able to clarify your description and come up with a satisfactory answer or repair. The most common cause of a true intermittent drop at the pedal is a defective seal within the master-cylinder assembly.

Looking for Overdrive Options
Q: Why don't ZF transmission builders add a double overdrive option to the ZF six-speed? This would help fuel economy and cruising and still have the super pulling power of the 4.10:1 gears. I have a 1996 4x4 Power Stroke F-250 with the ZF five-speed and a 4.10:1 rearend. My Power Stroke is fabulous at 141,000 miles, but at speeds of 65 mph, it turns over 2300 rpm.

A: The ZF Group, a worldwide leader in driveline and chassis technology, builds five- and six-speed manual transmissions for Ford light-duty trucks. Sounds like you've been considering buying a new Ford truck or perhaps swapping your five-speed for the six-speed, which came out with the 1999 Super Duty. But you then discovered that the five-speed's fifth-gear ratio is nearly identical to that of the six-speed's sixth, therefore defeating the purpose of considering the new transmission to lower rpm and increase fuel economy during unloaded highway driving. Gear Vendors, Inc. (800/999-9555; www.gearvendors.com) produces the Under/Overdrive auxiliary transmission, and U.S. Gear Corp. (800/874-3271; www.usgear.com) manufactures the Dual Range auxiliary trans. These units are commonly referred to as gear splitters and have two basic functions. One is to amplify towing power, the other to increase fuel economy. They actually supply shifts between shifts, with lower and higher ratios than the transmission was originally equipped with. This helps maintain rpm within the engine's peak torque and horsepower range while towing heavy loads. It delivers that extra gear you were looking for when the engine was either screaming in second or bogging in third. At the same time, you get that long-awaited double-overdrive shift (phase two of fifth gear), which may reduce highway engine speeds by as much as 22 percent. The 4x4 units bolt onto the transfer case with prices in the $3000-$4000 range (including installation). Speak with both manufacturers' technical representatives about pros, cons, and the details of each product's operation. You may never cover the cost with the extra fuel economy. You have to enjoy the driving upgrade to make it worth the money.