I think there is a problem with my transmission.

I have a hyundia elantra gt 2003 with 97,000 miles. This prob has been happening ever since 76,000 miles!!!.

When the car is cold it performs fine but after it warms up to the middle on the temp gauge it jerks when i get to 30mph and the rpm's drop. When my foot is on the pedal while the car is above 30mph the engine makes a lower pitched humming noise. and the rpms do not go up intill after 45mph.

Sometimes the rpm's wont even move but it will slowly go past 30mph

I can watch the rpm's trying to go up slowly but it keeps going down to 1500rpm or so. If i push the pedal hard the rpm's rev up to 3000 and the car moves faster but then jerks REAL hard and drops to 1500 again.

I will go past 45mph just slowly. after 45mph the car runs fine and the rpms dont jump around.


What could the problem be?

When the engine is cold it does not jerk when it gets to 30mph and it does not make the low pitched humming noise. Also the rpms go up when im on the pedal when it is cold like it should.

 

First, why would you wait so long? You put up with it for over 20K miles! If you are the original owner, go back to the dealer. The trans is covered under the 10y/100k miles warranty.

 

I think there is a disconnect in the thinking process somewhere.
You say the rpms don’t go up between 30 and 45 mph. They must or the car won’t speed up at all. Unless you are rolling down hill that is. Now if your rpm gauge isn’t keeping pace with the actual engine rpms that might make more sense.

Try ignoring your gauge. Does the engine sound match what the speed is?

I am suspecting you may have a bad rpm/speed sensor not a tranny.

 

Sorry.

The rpm's do move but only slightly.Like it is hesitating and does not know what it wants to do. they drop up and down while on the pedal trying to go faster. fluctuates between 1500 and 1800rpm.Sometimes the rpm's will not move when im on the pedal.they will stay at 1500 and the car does not speed up intill i push a little harder on the pedal and make the engine roar. But then the car jerks hard again and rpms go from 2000+ down to 1000.


from 0-30mph the engine sounds fine and matches the speed but after 30mph the car will jerk forward hard and the engine starts making a humming noise. the noise is very onnying so i have the radio on most of the time.

Acceleration is slow. cars pass me all the time while im trying to get up to the limit. especially at a stop sign or light. When i take off it is just so slow to reach the limit.


I dont really know how to explain this. this is why i have not brought it to a shop yet.


I also think i have bad motor mounts because the car and steering wheel shake bad while im at idle. Could that be the cause?

 

bump.

Anymore suggestions?

 

It may have been similar to a problem I had. The car would drive fine, then abruptly shift hard and stay in 3rd gear. After stopping at a light, it would take off very slowly, and when I finally hit a normal cruising speed of 45-55, the RPM's would be high and not go into 4th gear.

It turns out it was the Transmission Speed Senor. Since I was not sure if it was the Input or Output Speed Transmission Sensor, I replaced both. It is relatively easy to do. You just need to take off the air filter box, remove the bolts that hold the senors in place and replace the air box.

It took me about 20 minutes to do, of that I spent 10 minutes locating the sensors and figuring out what I needed to remove in order to get to the sensors (I like to plan my moves out). You will need some metric sockets, a ratchet, an extension, and a phillips screwdriver.

They one thing I must advise from experience is to use OEM sensors for the transmission. I used some aftermarket ones and they only last 9 months. I later replaced them with OEM ones and they are going strong for 2+ years. The sensors were about 80-95 each from my Hyundai dealer. I called the shop and they wanted $400 to do the job, so I saved about $215.

Hope this helps, and good luck.