In most cases, getting a transmission flush every 30,000 miles, or every two years or so is sufficient. However, there may be times when you need to get a transmission flush sooner, in order to help protect your car's transmission. There are some common signs that you need to perform a transmission flush on your car or truck.
Transmission Grinding or Strange Noises
A vehicle transmission that is contaminated with dirt, grease and sludge can display symptoms very similar to inadequate levels of transmission fluid. When driving your vehicle, if you notice your transmission grinding or making strange sounds, you should stop the vehicle and check the transmission fluid level while the engine is still running. Insure that the transmission fluid color is bright red and not brown or black because of grime or sludge. If the fluid level of the transmission is acceptable, your vehicle probably needs a transmission flush.
Problems Shifting Gears
Regardless if you drive an automatic or manual, your car requires clean transmission fluid that flows easily throughout your car's transmission. A transmission that contains too much dirt or sludge will cause sluggish response in the transmission which will result in your vehicle changing gears too quickly or too late while driving. In manual transmission vehicles, you may find it very hard to change gears at all.
A dirty transmission may cause a lack of hydraulic power, much the same as not having enough transmission fluid will cause. In order to stay in the appropriate gear, the transmission must develop enough pressure. When a transmission is too dirty, contaminants may interfere with the flow of transmission fluid that helps with this. If you're transmission has no other problems, and the fluid level of the transmission is full (or close to it), the problem is probably restricted fluid flow due to a buildup of dirt and contaminants that need to be flushed out.
Surging of the Vehicle
When your vehicle's transmission is polluted with a lot of dirt and contaminants, and needs a transmission flush, you may notice unexplainable surging of your vehicle. Because your car's dirty transmission does not allow for adequate transmission fluid flow, your vehicle may tend to jump or surge forward and fall backwards for no good reason. This is caused by inconsistent flow of clean transmission fluid that is needed to ensure smooth operation of the gears and other moving parts inside the transmission bell housing.
Delay in Vehicle Movement
Another sign that your vehicle may have contaminated transmission fluid is when the vehicle stalls for one or two seconds before moving after having been put in gear. If there are no other problems with the transmission, a transmission flush may help.
You should be aware that if the vehicle is displaying these symptoms, your dirty transmission may have already caused bigger problems.