April 1, 2003
Filed under Trailer How To
Q. My wife and I own a 1995 GMC 2500 Suburban 4×4, with the 7.4-liter TBI engine and 4L80E automatic transmission. The vehicle was one-year old when we purchased it and is now used primarily as a tow vehicle for our 2000 SunnyBrook CKL travel trailer. The problem is the braking on this vehicle. When the engine is cold, or while braking on icy or gravel surfaces, the Suburban is very difficult to stop. It feels almost as though it is being “pushed” during stops under the aforementioned conditions.
Usually, I shift the transmission into neutral to mitigate the problem. The front pads are new and the rotors are within manufacturer’s specifications, while the rear shoes are in great shape and are properly adjusted. The anti-lock braking system (ABS) was checked by the dealer in 1997 and a defective sensor was found and replaced. During icy braking conditions, or on gravel surfaces, I can hear the ABS chirp. Both my wife and I love this vehicle because it is great for long trips, and it provides a very stable and comfortable towing platform. Other than the cold or icy stopping problem, this vehicle is in excellent mechanical condition. Any ideas as to what is wrong?
— T.K., Parker, Colorado
A. I assume that you mean this problem occurs even when not towing (and the trailer brakes are working properly). It’s normal for the ABS to chirp or chatter a little when stopping on slippery surfaces; this tells you it’s working. However, the engine’s idle speed is probably too high, especially during the warm-up period, which would explain why you notice the problem more when it’s cold. Have the dealer check the idle speed when cold and hot, and adjust it to the minimum specification. The high idle speed is likely pushing the Suburban too hard and forcing the front brakes to skid when trying to stop it.
Ken Freund’s more than three decades of auto-repair experience and 20-plus years of RVing helped him author numerous books and articles on vehicle repair. In addition to RV Clinic and Performance, he writes the Powertrain column in MotorHome magazine. Ken has been a California Automotive VO-Tech and Smog-Test Program Instructor and an ASE-certified Master Automobile Technician.