FAQs—GMC C15 Suburban
Every time I shift my GMC C15 Suburban from parking to reverse, there's a loud clunking sound. What does it mean?
It tells you that something is wrong with your transmission, and you have to take action. A common cause of clunking sounds in the transmission is a low level of transmission fluid. The clunking is produced because the transmission's internal components lack the lubrication they need to enable your vehicle to shift smoothly. Your transmission fluid may be too old or contaminated and needs to be replaced. Check your fluid's color and consistency—it should be translucent and red or dark pink. If it is black or brown and cloudy, then you have to change it already. The clunking may also be caused by speed sensor failure. When it fails, it transmits incorrect shifting or speed information, leading to shifting problems and clunking while you shift gears. Failure in the transmission's internal parts may also cause the clunking noise and hard shifting.
Whatever the reason for the clunking sound may be, it is best to have your Suburban diagnosed by a professional because it involves removal of the transmission and taking each component apart to find out the problem.
When my Suburban is moving at an accelerated speed, it starts jerking before it goes back to its normal performance. It has stalled more than once, and it is really frustrating having to try to start my vehicle again, only to have it stall once more. What could be the problem and how do I fix it?
That is a clear sign that your fuel pump is in trouble. Fuel pump failure is often caused by fuel tank contamination, which is in turn caused by the moisture in the tank that develops rust. When fuel pump picks up the rust, it leads to premature fuel pump failure. The first thing you have to do is to get a fuel pressure gauge that you can use to check if the fuel pump sends the right amount of fuel to the engine. If it doesn't, then it is time to say goodbye to your good ol' pump. If its strainer is also discolored, you have to change the fuel also because it is already contaminated.
While accelerating my GMC C15 Suburban, it started shifting hard. It would not shift from first to second until I let off the gas pedal. Any ideas on what to do so that I can shift smoothly again?
You may want to check first the shift linkage and the clutch operation for any irregularity. Check also if you are using the right type of transmission fluid for your Suburban, as incorrect fluid selection can result in hard shifting. There may also be damage to internal components in your transmission in the form of metal flakes in the lubricant. You can have a better view of these flakes when you do your inspection by illuminating the area with a flashlight. If there are flakes indeed, then have your transmission fluid changed right away.