Rx300 Transmission Clunk/shake!

[tta300]

My '99 RX300 transmission clunks and shakes when shifting from P to D, or between R and D. The problem happened right after I cleaned the idle air control valve. I've done the following in the last few weekends, but did not fix the annoying shift shock.

-Cleaned throttle body

-Cleaned idle air control valve

-Replaced idle air control valve

-Replaced coolant temperature sensor

-Replaced transmission filter

-Drained and refilled Toyota type 4 transmission fluid twice

-Disconnected negative battery post overnight a few times to reset ECM

The problem disappeared for a day after I reset the ECM, but came back on the following day. The car runs fine and shifts smoothly while driving. I would appreciate any suggestions before I went to my dealer for diagnose.

[RX in NC]

That's a pretty comprehensive set of attempted fixes you've undertaken. I'm not sure that there's much more you can do yourself. But I do have a few questions:

1. How many miles are on the vehicle?

2. When you drained your original fluid, was it still pink/red or was it more grey or brown in color?

3. Did you notice any small metal shavings or particles in the original fluid?

4. Has your transmission fluid been changed at least every 30,000 miles using only Toyota Type T-IV fluid?

[tta300]

1. Miles on the vehicle--76,000 miles (bought new)

2. Old fluid color--pink/red

3. Small metal shavings or particles in the old fluid--negative, except the 3 pieces of magnet were covered with muddy stuff from wear and tear.

4. After the 30,000 miles service done by the dealer, I drained & refilled the tranny myself every 15,000 miles using only Toyota T-IV fluid.

If it is mechanical problem, why the clunk/shake disappears for a day after I reset the computer? Could it be the ECM going crazy? I just don't want to go back to my dealer, after I was told twice by them on some other issues, " They all do that!”

[RX in NC]

Don't rule out mechanical transmission problems yet because sometimes when transmissions are preparing to fail, they deviate back and forth between normal and problematic. But yes, your problem could also be electronic in nature as well. You've done all the right things in caring for your transmission given the notorious RX transmission history, and there don't appear to be any significant metal particles (which usually indicates impending gear failure) in your fluid. The best news for you right now is that the vehicle continues to operate normally, but the "clunk" that you describe when shifting could certainly be an ominous sign that you can't afford to ignore.

Before you do anything else, are you certain that your fluid level is correct? I've seen situations in the past where too much or too little fluid caused "clunking" noises and rough shifting in other (non-Lexus) vehicles. Adjusting the fluid level up or down as necessary corrected the problems in these cases.

As a next step, I think I'd look for a well-respected independent Japanese-oriented transmission repair shop in your area and pay a few bucks for their diagnosis. I hear you loud and clear when you say that you only want to return to your dealer as a last resort, but I think you've done about all you can do yourself. You've taken good care of your transmission and you deserve a simple and inexpensive fix. I hope you find one. Keep us posted here at RX Transmission Central....

[tta300]

Thanks for your valuable advice. Not until I realized RX300 was prone to engine sludge and tranny failure, I though it was a vehicle to keep. The cold/hot fluid level is correct at this time, but I'll find out if there is any improvement by adding/removing some fluid, 1/4 qt at a time.

[joensk]

Did you check the engine mounted and dog bone. My car have the same problem, I noticed that 4.1 qtz of transmission fluid seems a lot, Make sure the level of the fluid do not fill up above the top two notches on the dip stick and try disconnect the negative battery's cable again.

[tta300]

I just want to follow-up my earlier post. My Lexus dealer repaired the problem by replacing the throttle position sensor. Good job!