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The Most Common Reasons Why a Transmission Slips

Eddie spent 35 years in the automotive business with Honda. He is an ASE Certified Master Technician and has bruised knuckles to prove it.

We all know what an automatic transmission is, basically—very basically, at least—so I'm not going to bore you with the details about how it converts power from your engine into power at the wheels. But you should know that the process involves plenty of hydraulic fluid as well as gears and clutches.

If you don't know why your car’s transmission is slipping, I just might have the answer, though you may not want to hear what I have to say.

The cause of a slipping transmission will depend on the type of transmission you have in your vehicle. There are three types of transmissions: automatic, standard (or “manual”), and CVT (continuously variable transmission). I will discuss the two most common types, automatic and standard.

Why Is My Automatic Transmission Slipping?

If you have an automatic transmission and it "slips" while you are driving it—that is, the car engine revs without the power going to the wheels—the most common cause (though not the only possible cause) is low transmission fluid. If the slipping is caused by low fluid, it will get worse as the transmission gets hotter.

Why Is My Manual Transmission Slipping?

A standard (“manual”) transmission uses fluid too, but leaks aren’t a common issue; a standard transmission could lose all its fluid and never slip at all, though eventually, it would lock up while driving down the road. If you have a standard transmission, and it’s slipping—the engine revs but it doesn’t transmit power to the wheels—the problem is usually in the clutch.

Further down in the article, I discuss how to diagnose this problem.

Sounds Like Low Transmission Fluid to Me

What to Do If Your Automatic Transmission Is Low on Fluid

The next question is, why? Probably because you have a leak. Maybe you have noticed red transmission fluid in your driveway or your parking spot at work, but it didn’t occur to you that it came from your car. The cause of your leak is probably a failure of one of the seals that keep the oil inside the transmission (though there are other places the transmission might leak). How many seals the transmission has depends on whether you have a front-wheel-drive, four-wheel-drive, or rear-wheel-drive car.

If you do have a seal that is leaking, and you catch it in time before it damages your transmission, there’s a chance it might be relatively cheap to repair. Seals themselves are not expensive parts, but depending on where they are located, it might take a lot of labor to replace them.

If you have the leak checked out by your mechanic, and he tells you it’s just your axle seal, it could just cost you for a couple hours of labor, and you could be back on the road in a few hours if the parts are readily available. Axle seal failures are common, and the dealer will usually have those seals in stock. But if it's your input shaft seal, plan on leaving your car for a day or two, and expect the labor cost to be upwards of eight to ten hours.

Input Shaft Seal: Another Site for Leaks

Leaking input shaft seal.

Leaking input shaft seal.

This photo shows an input shaft seal leak. To replace this seal, the transmission needs to be removed from the car; this job can get costly.

Be sure to check your owner's manual on how to check your transmission fluid.

Be sure to check your owner's manual on how to check your transmission fluid.

Typically you fill the transmission through the dipstick tube, using a small funnel.

Typically you fill the transmission through the dipstick tube, using a small funnel.

Checking and Topping Off Automatic Transmission Fluid to Prevent Slipping

If your transmission is leaking, you will want to fix it. Meanwhile, if you must drive a car with a leaking transmission, you should top off the fluid.

Check your owner’s manual to see exactly how you should check your transmission fluid level. Some manufacturers will want you to check the transmission fluid level when the engine is warmed up and running with the transmission in park, other manufacturers like Honda will have you check it with the engine warmed up but not running. So be sure to read your owner's manual, DON'T GUESS!

If your transmission fluid level is low and not showing on the dipstick, add transmission fluid--the proper transmission fluid. Each car manufacturer uses a specific fluid. If you use the wrong fluid, you could damage your transmission internally, so again, check your owner's manual. Fill it to the top line on the dipstick and then drive it to your mechanic.

Note: Sometimes when an automatic transmission is low on fluid and you top it off, air pockets develop inside the transmission that keep the fluid from getting to all the parts of the mechanism. After adding the fluid, I suggest that while the car is running, you move the shift lever through the different gears on the shifter selector, and then check the fluid again. Running the shifter through the gears redirects the fluid to different parts of the transmission and removes the air pockets. You may have to do this procedure several times, or even drive the car around the block, and then recheck the fluid level.

Note: I do not recommend using additives that are supposed to stop leaks; they can plug up the transmission. Use the automatic transmission fluid your car manufacturer makes.

Read More from AxleAddict

How to Check Your Transmission Fluid

Other Fluids That Leak From Cars

If you are concerned about other fluids besides automatic transmission fluid that seem to be coming out of your car, here's some useful advice.

Clutch disc and pressure plate. The clutch looks like it blew apart. If you ride your clutch it may look like this.

Clutch disc and pressure plate. The clutch looks like it blew apart. If you ride your clutch it may look like this.

Common Cause of Manual Transmission Slippage: Worn-Out Clutch

If you think your clutch is starting to slip, you can try a stall test. Put your car in third gear and try starting off like you would normally, as if you were in first gear. If your clutch is working properly, letting the clutch out all the way should stall the car. If, however, the clutch is slipping, the engine RPMs will rise, the car will slowly start rolling, and you will have a smell like burning paper coming from the engine compartment. When a clutch starts slipping you will smell it. It’s like the smell of overheated brakes.

There are many reasons why a clutch would slip, but the most common reason is that the clutch is worn out. A clutch disc can last anywhere from 20,000 to 200,000 miles—it all depends on the way you drive—but like a brake pad, it’s a consumable item, and will be used up eventually, leaving the parts grinding metal-on-metal. If the clutch disc is worn out, you need to replace it, generally also along with the clutch plate and one or two bearings. If you don't replace a worn clutch in time, you might have to replace the flywheel (the big chunk of metal next to it) as well.

Riding your clutch—that is, leaving your foot on the clutch pedal when you aren’t using it—can really eat up a clutch disc fast, especially if you drive in hilly areas. Just being a newbie and learning to use a clutch for the first time can cause a lot of wear and tear. Learning to drive on a standard transmission can end up costing you money if you don't get the hang of it quickly.

Then again, clutches slip for reasons not related to wear and tear or abuse. If your input shaft seal is leaking gear oil onto the clutch disc, this could very well cause a slipping clutch. Another common reason for a slipping clutch is a faulty or damaged pressure plate. The pressure plate is operated by a high-tension spring. If for some reason the pressure is not distributed evenly over the clutch disc, the clutch will start to slip.

Blown Clutch: It's Completely Worn Out

I Appreciate Your Questions!

There are many possible reasons for a slipping transmission and I could not cover all of them above. If you have any questions just leave them in the comment box below.

This article is accurate and true to the best of the author’s knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.

Questions & Answers

Question: I have a 2011 Chevy Silverado 2500 HD. This morning, as I was driving about 30 mph, the engine started to roar as if in neutral. It did this about three times for about a mile until I could get home. I later drove around the neighborhood and it does seem to make a vibrating noise at times, and it also seems like it is shifting at times. The fluid level seems normal. It is a used vehicle that we purchased three months ago, so I know nothing about the history. What could this be?

Answer: If the fluid level is OK, it's possible you may have a solenoid or valve that is sticking or not working properly.

Question: I have 2012 Silverado, and the transmission slips while driving. If I stop and restart the engine, it drives fine. Do you have any idea what this could be?

Answer: It sounds like something electronic, like a solenoid or valve, so it could be a quick fix.

Question: I have a 2003 Impala which I had a rebuild done on in February 2016. Now (out of warranty) the car fires up and goes into any gear without hesitation for about 30 seconds then makes a noise and all of the gears go out. I turn the car off and restart it and then it will again work for about 30 seconds?

Answer: I recommend brining it back to the shop that did the rebuild. It sounds like you have an electronic solenoid that is failing.

Question: I recently had my transmission refurbished when I noticed a small leak and the car would switch from first gear to neutral for few seconds and then back. Do you know what's happening or what I should do?

Answer: You should bring your car back to the shop that rebuilt the transmission and have them check out the leak and the slipping. If it's a reputable shop, they should have some kind of warranty.

Question: My Cherokee XJ transmission only slips on super humid days in the rain. What do you think the cause of this could be?

Answer: I don't think it's your transmission, It sounds more like a skip in the engine, and that would make more sense.

Question: My Honda Accord 2007 shifts weird only in the morning. Sometimes it won’t shift into gear or hard shift. I have a leak on my axle seal. I replaced the seal, but it still leaks. My mechanic says I have to change the cv axle because it's leaking. What should I do?

Answer: I recommend a second opinion on the leak. A mechanic can very easily damage the axle seal during installation, and it would be very unusual to have to replace an axle because of this leak.

Question: I have a 1999 Honda Civic, and I recently changed the clutch and pressure plate, but I'm getting clutch slip. Any ideas on what to try next?

Answer: Yes, I recommend replacing the rubber hose in the hydraulic system, if the hose collapses inside the clutch will lack pressure when releasing the pedal.

Question: Just bought a Honda Accord 99 V6 V-tec and it has a slipping transmission. Where do I start?

Answer: I alway recommend starting by checking the fluid level and condition. If it's black, replace it a couple of times and see if it helps.

Question: Is there any chance to fix and recover my slipping transmission instead of purchasing a new one?

Answer: If your transmission is slipping, start with the basics. Check the fluid level and condition, address as needed. If the check engine light or check transmission light is on, have the codes pulled, it will point you to what is going wrong with the transmission. Sometimes a filter and fluid change can correct slipping issues, sometimes the problem will need more diagnosis.

Question: I have a 2004 Honda Pilot with 262,000 miles on it. For the past four years, maybe once or twice a season it would slip out of drive after a stop. It either shifted to 2nd gear, or turn off. Restarting the car would remedy the problem, and then it would not happen again for weeks or months. This past year, it happened a few times, and then not for days. Lately, it's happened quite often until I had my power steering pump replaced. Since then, it has happened only once or twice. Does this make any sense?

Answer: It sounds like you may have an electronic solenoid failing. If the check engine light is on or the "D" light is flashing, have the codes read, it will point you to which solenoid is failing.

Question: I have a 2003 Honda Accord EX. It has 185,000 miles and has a transmission issue. When I take my foot off of the accelerator for a couple of seconds, the transmission immediately wants to downshift. I have an automatic transmission. The transmission does this at slow and fast speeds, but not so much above 50 mph. Is my transmission bad, or do I have bad solenoids?

Answer: If the check engine light is not on and the "D" light on your PRNDL2 is not flashing then you know it's not an electronic solenoid failure or issue. If the fluid is dirty or not at the correct level, this could also cause some issue like this. Honda transmission fluid levels are checked with the engine off and the car on level ground. Only use Genuine Honda transmission fluid, or you will have shifting issues.

Question: I own a Toyota Axio, and it uses CVT fluid. It's not accelerating as fast as it should when I press the gas pedal. It does so only momentarily before going back to normal. I have replaced the spark plugs, cleaned the throttle and replenished the CVT fluid to a reasonable level, but nothing has helped. Does my gear need replacing?

Answer: No, I don't think so. Look to see if the check engine light is on.

Question: I have a 1994 Honda Accord Automatic. It starts and drives about two blocks. Then, as soon as I stop and start to accelerate again, there is no movement. If I turn the car off for about 5-10 minutes start it back up it drives again for about a block or two, then it stops. I've checked TCU transmission fluid and code lights. Any idea what it could be?

Answer: It sounds like your transmission has a clog. I recommend using light compressed air through each check port on the transmission and see if you can move the debris around.

Question: What would make an automatic transmission not engage if the fluid is full?

Answer: It's usually a lack of pressure. The problem could be a pump, filter O-ring, blocked passage, etc.

Question: When I shift, my car revs up before speeding up. Is the clutch going out?

Answer: It's possible your clutch is going out.

Question: My 2008 Ford f150 like thumps a little when running 45 or so. It doesn't jerk or rev, it just feels like someone has a rope tied to the back and giving it a quick little tug. Is that my transmission?

Answer: It could be but it sounds to me like maybe a bad spark plug, plug wire, coil or something to do with spark, it's just a hunch.

Question: I have a Newly rebuilt trans on a F-250 7.3 2001. First and second gear seem to slip when trans oil temp reaches 190. It was taken apart 3 times and no issues were seen. A triple disk converter was added. Any ideas?

Answer: You're losing pressure somewhere, it could be an o-ring, crack in the valve body, a valve not closing all the way. Do you have another valve body you can swap out?

Question: I have a 1994 Chevy 1500, and it slips when it is hot. What could the problem be?

Answer: What is the condition of the fluid and the color? If the filter hasn't been changed in a while it's possible debris is collecting in the screen and causing a flow problem. I recommend starting by checking these items.

Question: I have a '98 Corolla manual. Lately, I've noticed it revs high and is sluggish in first and second, but is fine once it's in third. Could there possibly be a vacuum leak?

Answer: The high rev could be a vacuum leak at idle. The sluggishness is more likely a bad spark plug or spark plug wire. A bad spark plug or spark plug wire will fire well under a load, but once you get the vehicle up to speed, the engine will run smoothly.

Question: I have a 2001 Dodge Ram. If I romp it to the rug, it gets to about 4-grand and then acts like it goes into neutral. What could be the cause?

Answer: Sounds to me like your losing pressure inside the transmission and it is going into neutral. Have you checked the transmission fluid yet? Also check the condition of the fluid, if it is very dirty the pickup screen could be restricted.

Question: My 2003 Honda Pilot is slipping and static shifting after I drive it hard for ten minutes. When you first drive it, it doesn't slip or shift hard. Could it be the shifter solenoid or overdrive solenoid?

Answer: The most common condition people overlook is the transmission fluid. The fluid is either too low or very dirty. Dirty fluid can cause all kinds of shifting issues because it clogs up small passageways going to the shift solenoids. If the fluid level is low, there's not enough fluid to fill all these passages, and the transmission lacks pressure internally. This will lead to poor shift quality or no shift at all. So I recommend checking those two conditions first.

Question: I have a 2004 Ford F150 Heritage with 186,000 miles. After a warm-up, as I brake the truck shutters as it comes to a stop and then stalls. I can restart the engine, but unless I rev the engine as I shift to drive, the truck stalls again. Is this problem the torque converter, one of the sensors (I've replaced the 2-speed sensors) or the trans itself?

Answer: Most likely the torque converter is stuck in lock up, so it could be the lock up solenoid or something internally wrong in the torque converter.

Question: I have a 5.2 liter, Dodge 1500 truck. I took the pan off and cleaned the valve body. I also adjusted the bands. Now, when I take off, it doesn't slip, but at about 20 miles an hour it locks up the rear tires. What's causing that?

Answer: I think you adjusted the bands incorrectly. I recommend consulting a transmission expert, someone who knows Dodge transmissions. It sounds like you're pretty mechanically inclined, so if you pick the transmission expert's brain, they should be able to get you rolling again.

Question: My transmission is squirting gear oil on my clutch. If I put a new seal in, can I use the old clutch, or do I have to buy a new one?

Answer: I recommend replacing at least the clutch disc, but it's best to replace the assembly. You already have everything apart, and you're looking at about $150 in parts.

Question: What should I do when my cars automatic transmission is shifting abnormally when it gets hot?

Answer: I always recommend checking the fluid level and condition first. If it dirty or low, change it or top it off.

Question: My 2013 Ford Focus sticks at a high rev when I am on the highway and accelerate to pass. It hangs up there for maybe three seconds then comes back down - when I am going 70-75. What gives?

Answer: I recommend checking the throttle linkage and throttle plate for any carbon build up. Try cleaning up the plate with carb clean and clean the inner and outer moving parts as well, then use some spray lube on the external moving parts.

Question: My 2000 Tundra's rebuilt automatic transmission has about 70,000 miles on it and began slipping, but has no transmission leaks. Can this be adjusted out, or does the transmission need to be replaced?

Answer: It's best to have a transmission expert or a Toyota tech check it out. Sometimes a sticking valve or solenoid can cause a slip. Also dirty fluid could also cause shifting problems.

Question: I have Lexus ES 2011. The auto transmission is having some issues with hanging and then suddenly shifting with a slight jerk move from 2nd to 3rd or 4th gear. This happens in between 40, sometimes 60 to 65 KM/H. Also, the RPM needle sometimes goes slightly up or down in a shaky movement by itself. Any suggestions about what it could be?

Answer: You should maybe have the transmission serviced, or you can check the fluid level and overall condition.

Question: I have a 2005 Chevy TrailBlazer LT 4.2L with 167,000 miles. My transmission started slipping when going into third gear but I can’t check my fluid because my dipstick broke in the tube. How do I check my fluid level?

Answer: You can remove the dipstick tube from the transmission, it it either pressed into the transmission housing or there is a bolt holding it into the case. Remove the tube and buy a new dipstick.

Question: How do I adjust shifter arms on a 1991 Honda Accord?

Answer: There is no adjustment on shift arms on a 91 Honda Accord.

Question: I've got an 83 Yamaha Maxim 750cc. It doesn't slip per say, but it pops out of first gear and back into neutral on its own. It only does this from first gear, and it happens more frequently as the engine warms up. What could cause it? I Haven't checked the clutch cable to see if it's loose, but the stall test is fine. I'm at a loss

Answer: Usually, when a transmission pops out of gear it's because a shift fork is bent inside the transmission. The shift fork is what moves the synchro up and down the gear, and if it becomes bent for whatever reason, it will slip out of gear.

Question: My 2005 Honda Civic automatic transmission 1.7 engine is jumping while shifting but not revving up. Today it popped out of gear, and the engine was still running, had to coast to stop. Put it in park, reverse, and then drive, went into gear and drove home, it jumped a few more times, so I manually shifted until I got home?

Answer: I recommend checking the fluid level and condition first. If the fluid level is low, top it off, if it is black or gray, I recommend changing the fluid a couple times and see if your situation improves.

Question: While accelerating, my manual transmission seems to slip. Would that be the clutch or a deeper issue?

Answer: On a manual transmission, the only way it can slip is from the clutch. If you start from a stop in second gear and the clutch doesn't grab the point and almost stalls the engine, then most likely, the clutch is on it's way out.

Question: Are there any other problems aside from the clutch disk that could make my RPM go high with low power?

Answer: If the pressure plate is weak it can cause the same issue, also if any oil gets on the disc it can cause it to slip.

Question: I have a 2012 CRV. Five weeks ago, I had a bad skid on ice and hit a steel grate built into the sidewalk. This caused approx 9000 dollars in damage to the tires, wheels and suspension systems. I just picked the car up, and it is jerking when I drive about 30-35 mph. When I drive from 45-50 mph, it stops. Is this a transmission problem, and could I have caused it when I hit that grate?

Answer: If the problem wasn't there before you hit the curb, it might have something to do with either the accident or it sitting so long. I recommend bringing it back to the shop that did the work and take them for a test drive to show them the problem, maybe it's a quick fix. I would also let your insurance company know what's going on and keep them in the loop.

Question: The input shaft seal of my Toyota Corolla broke. The ATF was lost, and I have since replaced it. But now the transmission is slipping. What could be the cause?

Answer: Be sure to check the owner's manual for the proper procedure on how to check transmission fluid level; not every car is the same.

Question: Even since I've changed my transmission fluid, I've been getting about 5-6 mpg less. The transmission is slipping, and sometimes it falls into neutral when downshifting. I've checked the levels while the engine was running, and it's about 1cm above the full line. Also, it seems to be driving at higher RPMs than usual. What could be the problem?

Answer: On some vehicles, the engine should be off and the car on level ground before checking the transmission fluid level. I recommend you check your owners manual for the proper way to check the transmission fluid level.

Question: The fluid itself isn’t super low, but does seem old, can this be causing my automatic transmission to slip?

Answer: Absolutely. I recommend checking the transmission for leaks first, then doing a transmission fluid change. It's a cheap test to see if the shifting improves.

Question: Can I use Valvoline CVT Full Synthetic Continuously Variable Transmission Fluid in my 1999 Mercedes Benz automatic transmission?

Answer: No, use the recommended Mercedes Benz transmission fluid.

Question: What would cause a 4l65e transmission to, while traveling down the highway, all of a sudden jump out of drive? 1st gear is great, 2nd gear starts good, but then it starts a grinding noise until my speed reaches 25-30. Then the grinding noise stops as I shift into 3rd gear at 40 mph. It drives fine until I go back down to 40, then it slips out of gear. There is no 4th (drive) at all; I can only manually shift.

Answer: It sounds to me like you have some internal problems with your transmission, and it will probably need to be disassembled to find the cause.

Question: My fifth gear engages, and l can drive while l am supporting it, but when l let go of the shift lever it goes back to neutral. You can push it back to neutral without stepping the clutch. What is the problem?

Answer: The shift fork for that synchro is most likely bent.

Question: Why is my transmission slipping into fifth gear? I bought a new fifth gear and its sleeve, but the transmission is still slipping.

Answer: If the gear is staying engaged but the clutch is slipping, then most likely the clutch is slipping, not the gear set.

Question: I just changed the fluid in an automatic transmission. It didn't seem to have any type of slipping, but it does now. I know a lot of times it will break down pre-existing stuff and cause problems. My question is, is it possible that it's just working the new fluid into the transmission? Maybe there were air pockets from when I drained it, and it's possibly filling them?

Answer: No, the fluid is not breaking in. Have you checked the fluid level? Sometimes after filling it, there are air pockets, so you need to take a short drive ( one mile) and recheck it; sometimes 2 or 3 drives before all the air is out and the level is correct.

Question: When I was driving in 5th gear, the car revved up, but didn't gain speed. Then when I came to a stop, there was nothing, no gears. Is that the clutch?

Answer: If the car has a standard transmission, it's possible your clutch disc failed, or the pressure plate is broken.

Question: I have a 2010 Jeep Grand Cherokee that is slipping between 30-40mph, but only when the rpm is low (2000 rpms.) When I’m up to over 3000 rpms, there is no slip. What is my problem?

Answer: It might be the engine skipping or hesitating.

© 2011 Eddie Carrara

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