I have a 2001 Santa Fe 2.7 V6. While driving at cruise speed the (in 4th) the trans will suddenly drop into 3rd gear. This usually happens with a severe "thump", and then locks into 3rd gear. I have to pull over, turn the car off and wait for a bout 30 second. before I can restart. normally it it will be fine for a while, but every so often it will reoccur about 5 minutes later. and I will have shutdown again to "reset" the transmission.

I have taken the car to several trans specialists and to the local Hyundai dealer and they cannot find anything wrong with the transmission. The specialists have service the transmission (replaced belts, filters, strainers, oils, etc, and reset the computor) and the problem still occurs. The Hyundai dealers have run a full diagnostic on the car and found nothing, They say they have never heard of this occuring before.

Over the last month, the car has been to the service center about 8 times with the same problem....

Does anyone know what the cause could be? and how I might get it sorted?

 

How long do you drive before this happens? We traded in out 03 Accent, Had similar problem. But never stayed locked into 3rd. When the engine/trans would heat up for a long consistant drive, ie drivin from MD to VA, we would try to pass somone and it would be like "KNOCK BAM KNOCK" Then suddenly be fine again. Kinda scary but i dunno if its the same problem yo are having.

Dealers couldnt find anything out on ours either.

 

I can drive the car for about a week about (work and back) about 45 min iether way, without a an occurrence. I would the drive to the mall at lunch (one day) and then have to drive home in the evening and then the trans will suddenly lock in 3rd. it is a total random thing. Sometimes it would happen only once (have to shutdown and restart) and sometimes it would hapen about 3 to 6 times within 5 min's.

Mine would be BAM lock into 3rd. If Duke's advice sorts this out, I will be one up on our dealers over here... One for Hyundai owner - Zero for Hyundai...(LOL)


I got the following advice from Duke:

"The tranny is locked into 3rd, because the TCM has recognised a sensor fault. It generally is caused by a signal glitch of the output speed sensor (PG-B). This could be just a poor contact at the sensor, or the sensor tip is contaminated with some metalic dust (which is normally ocuring, since this sensor point at the output gear). There is generally a code in the TCM, but not always, specially when the problem hapen intermittently.
Have the tech remove and check the speed sensors, PG-A & B."

Hope his advice works... Even considering replacing the auto trans with a manual trans at the moment, as I am at my wits end. The car is in as we speek, I need it for the weekend, I have to tow a trailer with some Quad bikes and jetski's to the dam.