Automatic Transmission Jerks Before It Shifts

My car will be driving normally, then sometimes when I start to speed up a little, the engine will rev high (between 4K and 5K RPM) and then jerk into gear.

The check engine light has come on before but then gone off.

Do you think this could be my transmission?

Colleen

Hello Colleen,

Yes, this does sound like you could be facing automatic transmission problems. First things first though, you should get someone to check the transmission fluid level and top off if needed.

Low transmission fluid is the main cause of most transmission complaints. The fluid gets low, due to a leak somewhere, and the pump inside the transmission can not pump enough fluid to the internal parts thus shifting and slipping problems arise.

If you have to add more than just a cup of fluid, you most likely need to find and repair a transmission leak somewhere or the problem will happen again. Just like the engine oil, its harmful to the transmission to run low or out of fluid and permanent internal damage can occur.

If the fluid level is fine, I would consult with a few local transmission repair shops in your area before you did anything else. You probably have an AAMCO transmission shop in your area.

Having this transmission fluid “flushed out” or changing the transmission filter could actually make the situation worse, so talk to a few qualified transmission shops before you do anything yourself.

The fluid over time becomes dirty/gritty and abrasive due to normal internal wear, but if you remove that abrasiveness and install new fluid the clutches start to slip or they slip much worse than before the fluid change. Any vehicle over 100K miles that has not had a transmission fluid service is likely to do more harm than good changing the fluid and filter.

Check out how complex the internal working are on an automatic transmission

There are some internal and external shift solenoid on many vehicles that can fail and cause no shift or late shift patterns, so you could have an issue with a solenoid that the repair shop will need to look into.

Older vehicles used a vacuum source to shift gears, and if the vacuum hoses or the vacuum source on the engine failed the transmission would not shift. A vacuum modulator located on the transmission was a very common failure, especially on Ford vehicles. You could remove the rubber vacuum hose attached to the modulator and if fluid came out it was bad and needed replacement.

Now days, just about everything on the vehicle and transmission is electronically controlled…sigh.

If you do not have a relationship with a transmission shop, talk to your regular mechanic and to friends and co-workers to see whom they recommend and do not recommend.

Most people will only have to deal with a transmission shop once during the life of a vehicle, so the opportunity for shady dealings is higher than at your regular mechanic whom you might deal with on a monthly basis and he relies on repeat customers and referrals for his business.

Some of the U.S car manufacturers offer a rebuilt transmission to be purchased in their parts department. You can buy it from the dealer and have your regular mechanic install it for you, which should save you money over a dealer labor rate mechanic.

You usually get a much better product, with a national warranty honored at ANY dealership. Yes, it will cost you a bit more, probably just a few $100’s but to me a better product and stronger warranty would be worth it.

And, one other added benefit is the time savings. If the dealer has the transmission in stock, you can have it installed in just a few hours, not days to overhaul yours at a local transmission shop.

Now as far as your check engine light, it could be related to the transmission issue, the computer is seeing the high RPM and late shift pattern and probably making a note about it and storing a code in memory.

Please share this with your friends,
Austin Davis