Transmission slips — what you need to know
Symptoms of a slipping transmission
• Engine revs or chugs — You try to accelerate and RPM pick up but you don’t feel a corresponding increase in speed or the transmission “chugs” with grip/release feel
• Slow, weak or delayed acceleration— You feel a delay between the time you press the pedal and the time the transmission picks up speed
• Difficulty shifting gears or hard shifting— The transmission shift later than usual or slams into the next gear
• Grinding, whining or other strange noises— Self explanatory
• Won’t go in reverse
• Burned or strange smells— A transmission slip is often caused by slipping clutch discs. When clutch discs slip, they can overheat, causing a burning smell
• Check engine light and a transmission related trouble code.
Every day I get questions from readers about transmission slipping and they always want to know if a transmission fluid change will fix the problem. If you’ve neglected your transmission to the point where the fluid is a dark brown, a fluid change will NOT fix your transmission. This isn’t even a case of “what have I got to lose by trying it.” It’s simply a total waste of money with almost NO chance of making the transmission better. In fact, adding fresh fluid to a neglected transmission has a very high chance of totally destroying it. The fresh fluid will dissolve the varnish buildup from the burned oil and that can clog up everything.
Causes of transmission slip
• Low, worn out or burned transmission fluid— If your transmission is low on fluid and you drive with low fluid, the internal friction of the clutches and gears can overheat the remaining fluid, causing it to “burn” and degrade. The degraded fluid can’t lubricate as well, causing clutch and gear wear, as well as seal degradation
• Solenoid problems— Modern transmissions use solenoids to pulse fluid pressure to operate valves and clutches. A failing solenoid can cause a loss of pressure which then causes transmission slip
• Worn or broken transmission bands— Transmission bands have a coating of clutch material to grab and hold rotating parts. When the transmission fluid degrades, or a solenoid doesn’t apply the correct pressure, the band clutch material can slip, causing band damage.
• Clutch problems— Worn clutch discs and steels can cause transmission slipping issues
• Worn out gears
• Torque converter issues
Will a transmission fluid flush fix a slipping transmission?
Rarely. In the cases where a transmission fluid flush fixes a slipping transmission, it’s often because the transmission fluid was low due to a leak and the new fluid restored the proper level.
Will a transmission additive stop a transmission slip
If your car is an old junker and you only need to get a few more months of driving out of it, then by all means, pour in a can of transmission fix. That stuff works by swelling the rubber seals and that can improve the shifting. But only for a little while. It’s going to fail completely—and soon.
If you drive an older car and the transmission operates well, you can extend its life by adding a transmission conditioner like Lubegard, ProLong, or Lucas Transmission Fluid conditioner. If you drive a late model car that uses synthetic fluid, you won’t benefit from any of these products.
What’s the bottom line on fluid flushes?
If you’ve neglected your transmission and the transmission is slipping and the fluid is dark brown and burned, a fluid flush may actually make it worse.That’s because the flush washes out any crud in the cracked/degraded seals, making them leak and lose pressure.
However, if the fluid is in good condition and the transmission is shifting properly, a fluid flush shouldn’t harm it, even if it’s been neglected.
© 2012 Rick Muscoplat
Posted on by Rick Muscoplat