Dear Troubleshooters:
I recently purchased a '99 K2500 Silverado Extended Cab to pull my travel trailer. I noticed that when on hills and under load, the transmission will make a chattering noise that stops when the load is relieved or when the transmission upshifts.The vehicle is equipped with a transmission temperature gauge and a tow/haul feature. The transmission temperature is normal at approximately 200°F to 210°F; the vehicle speed is between 40 to 50 mph when the noise occurs.
The fluid shows no sign of heat, and the transmission shifts and operates just perfectly other than the noise. I am worried that there may be trouble on the horizon and would like to have the transmission checked out under warranty. But I will not be able to duplicate the noise unless I drive the technician up the hill with my trailer in tow.
Here is the vehicle information.
The vehicle is equipped with Z71 off-road and tow package and has the built-in transmission temperature gauge with the heavy-duty transmission. If you have any information on this, please let me know.
Dave Downing, Medford, Oregon
Dear Mr. Downing:
There is a TSB concerning this problem. Chevrolet calls this "launch shudder" and describes the condition that you are experiencing to a 'T.'The fix is to replace the current two-piece proper shaft with a new one-piece design. The driveshaft center bearing and housing also must be removed to install this replacement shaft.
Obtain a copy of TSB #01-04-17-001 dated Feb. 2001. This will explain the procedures needed to correct that chatter.
Dear Troubleshooters:
I have a 1996 Chevy 3/4-ton 4x4 pickup with 40,000 miles on it. It was purchased used a few months ago with 36,500 at that time. Just last month, I had the oil, oil filter, fluid levels changed/checked and some front-end alignment work done by a local repair facility. They said I was "good-to-go" on my Canada fishing trip.Everything went well until the return trip, when the transfer case began to chirp and growl continuously. I had to leave the truck with the local GM dealer and continue on home. When I got the call from them, the dealership said the transfer case had almost no oil in it and was wet on the outside from top to bottom. I checked back at the repair garage where I took it for the lube job, and of course they said it was full and showed no oil leak problem. They replaced the transfer case with a new one and $2,000 later I had my truck back.
I asked them what caused this problem, and they said it lost its oil. I asked them, "How?" They didn't have an answer, but they had to return the transfer case to GM for inspection. I understand that this style transfer case has an oil pump in it. Have you heard of any related problems with this transfer case?
If you have any information on this, I would greatly appreciate it.
Ray Krebill, The Able Co., Wyoming, MI
Dear Mr. Krebill:
There are several ways that fluid could have escaped from the transfer case other then by obviously worn seals or gaskets.If the unit was overfilled when adding or replacing the lubricant, resulting pressures would push the fluid out of the vent tube.
If the vent tube was damaged or somehow blocked with a foreign substance during the course of your fishing trip, the internal pressure build-up would result in leakage past even good seals and gaskets.
If the vehicle were driven for a length of time at road speeds on a hard surface while in four-wheel-drive, the heat and resulting pressures could cause the fluid leakage.
There is a TSB # 86-74-04 concerning a damaged transfer case input seal. This would allow fluid from the automatic transmission to be pumped into the transfer case and could cause excessive transfer case pressures and leakage.
However, you do not mention any automatic transmission-related problems, such as erratic shifts or slippage, which would have resulted from the low transmission fluid levels.
