So it's been a while since you last changed your transmission fluid. In fact, it's been so long that when you checked the transmission fluid dipstick, the fluid not only looked burnt, but it also smelled burnt. With fluid like this, most experts claim that changing it at this point may do your transmission more harm than good. If you're wondering why, the following may shed a little light on the issue.
How Fluid Wear Occurs
Automatic transmission fluid contains a wide variety of friction modifiers, detergents and other ingredients that help lubricate and cool the transmission. The fluid also acts as a hydraulic medium of sorts, pushing against a set of pistons that help actuate the transmission's clutch pack. The clutch pack is a series of clutches and bands that help with gear changes under normal operation.
Over time, the fluid will lose its friction modifiers due to ordinary wear and tear. If you don't change your fluid according to the recommendations in your owner's manual, the worn fluid could cause the friction material on the transmission's clutch packs to overheat and subsequently wear away. As the metallic clutch pack material wears away, it becomes suspended in the transmission fluid, contributing to the fluid's dark color.
Creating a Slippery Situation
Draining the old transmission fluid and adding new fluid may restore the lubricating and cooling properties your transmission needs, but committing to a "drain-and-fill" procedure could rob your transmission's clutch packs of the friction they need to operate properly. As new fluid circulates throughout the transmission, the fresh detergents can wash away loose clutch pack material.
Without the suspended clutch pack material, the worn-out clutches and bands may begin to slip against one another, regardless of how much pressure is applied by the transmission fluid. This may prevent your transmission from engaging in gear properly no matter how much fresh fluid you add to it.
Prevention is the Best
Once your automatic transmission fluid takes on the characteristic burnt odor and extraordinarily dark color, the damage may already be done. Your only option at this point may be to have the entire transmission rebuilt or replaced, which could be a very expensive undertaking, in most cases. This is why preventative maintenance is so important when it comes to caring for your vehicle's automatic transmission.
Most experts recommend that you check and change your automatic transmission fluid at least every 30,000 to 100,000 miles. If you regularly tow trailers or haul heavy loads, then you may need to check it more frequently than this.
Not changing your transmission fluid when you're supposed to can have consequences for your vehicle, so it's a good idea to follow the above recommendations. Check out an auto shop like Performance Parts Classic Chevrolet for more information.