At times I will notice my tranny shifting extremely firm and at the wrong shift points. It will not downshift when it should or slam into the next gear. I can simply turn the car off and back on and it is back to normal. It seems I am resetting the TCM or something. Any experience with this?

 

Transmission are hard to diagnose when it comes verbally... But the first thing when it comes to transmission problem is to check the fluid condition and simply replace the fluid with new. If it still does it then you got an internal problem. If it's electrical, CEL will come on. So, try changing the fluid.

 

Do a FULL fluid flush, meaning 2-4 qts at a time; drive the car and then do it again 2-4 qts.

I dont have the numbers but the first drain/refill leaves something like 85%, 2nd leaves about 70% old fluid etc etc. Try this first as its the cheapest alternative.

 

Been doing some research on the Lexus and its tranny issues. I've come across some threads indicating the transmissions health is at times directly related to the battery. Strang concept as I never knew a car's transmission rely on such a thing. Apparently, Lexus' and possibly other luxury makers are designed this way. May seem like a strecth but check your battery terminals and clean if needed, as well as what the others mentioned about the drain and refill cycles. See where these cheap alternatives take you.....

 

Thats true. A weak battery will cause weird problems. Get it load tested to confirm its good

 

Don't change the fluid just make sure it's full, if you Chang the fluid you will need a new tranny that's for sur��

 

when the car is driven, its running off the alternator. so the battery shouldnt be the issue, right?

 

The alternator will charge the battery regardless; but if you want to know if the battery is still good, you would need to do a load test.

 

what does this have to do with the transmission?
that was my question

 

There's some threads on here about the battery and the tranny being related to some degree. There was a member on here (can't remember his name) who had indicated that he had been through three transmission replacements. When he researched the root cause, he discovered that it was the battery causing the weird shifting issues and what not which ulitmately lead to his tranny failures. FYI, I have heard of this issue regarding tranny issues due to improper voltage coming from the battery from other forums while researching this, so it's certainly not just a moot thought. Now your problem could be something else, but I would check the fluid and make sure that is good as well as tesing your battery for proper voltage. Its a start and could save you loads of money....

 

Will give the sensors wrong readings and the PCM is gonna give out a false signal to the transmission. So it will not shift properly.

 

Yes, ive seen this thread but forgot the name or else i would have posted the link here.

 

i see now. it's more like a bad battery terminal clamp issue. when the car is running, the alternator puts out 14 something volts regardless of battery voltage. or the battery post is corroded, and that it may reduce voltage.

so bad battery post or bad terminal clamps, right?

 

Same here. I came across it while searching but can't remember the word that was used to search

 

It's worth a try. Why not? Clean the terminals but also check the fluid as well