probex

I have a 99 RX300 AWD with 48,845, and I have noticed that everything I change the gear to drive or reverse it jerks and at the same time the RPM meter goes up and down after a second. It runs and drives very good when hot. The problem exists only when the engine is cold, and I have been experimenting in the morning by letting the RPM needle drop below 1 before changing the gear. It seems to still give a slight jerk. I am worried because I feel like most RX owner had transmission problems, because something was not done in in the early stages, to prevent this problem, and I don't want this transmission to fail. I feel like it will fail if I don't do something now. I have no fault codes. I want to know if a part needs to be replaced or updated such as the idle air control, some kind of sensor , cleaning the throttle body or using a fluid to thin my existing tranny fluid. What do you guys think ?

salimshah

Welcome to CL.

Congratulations for having a least used vehicle ,,, unless you dropped a digit or two


Some questions before we attempt to answer your questions.

Do you park at a flat horizontal place (no incline)?

When was the transmission serviced last (hopefully no flush)?

What is the condition of transmission fluid ,,, color/smell?

What are the normal idle speeds (cold and hot).

Do you use parking brake in this order:
Come to a stop, engage parking brake, move the shift lever to Park, shut off the engine.
Start, wait couple of secs, engage in R or D, release parking brake, drive off.

Salim

probex

The car is flat and the tranny fluid is perfect. It has a pink cherry look to it. The transmission didn't need to be serviced. It really was an old person's car and they didn't use it. The normal idle rpm is below one but as I stated before this only is happening when the engine is cold in the morning. I have left it in for 10 min to properly warm up before shifting into drive and it did the same thing. I suspect that the tranny fluid needs to be warmed up to avoid this, or the tranny fluid needs to be thinner in order to go to certain parts of the transmission, because during the day it is a perfect car. I am thinking this is the flaw with the Lexus tranny. There must be a way to prevent a failure in the future if I can do something now.

rufftimo

Just joined today and found this thread, as I'm having the same problem, a hard shift from Park to Drive. All other gears shift smoothly. Gonna drain and refill the fluid, drive 500 miles, then repeat and report back here on color of the fluid.

copperny

even though fuel injector vehicles don't need a warm up period like a carburetor vehicle, IMO best practice is to let vehicle run for 60 secs let the fluids circulate before driving off and be gentle with the gas pedal till you reach operating temp. Hey horses get warmed up before they race and out the gate at full throttle same thing for your vehicle.

sktn77a

iTrader: (2)

It could be an issue but it's more likely just due to the high RPMs when cold. A perfectly functioning transmission would not do this but an older one (despite the low mileage) might well. Does it do it worse when starting on an incline?

ricco750

Do you know if your Idle Air Control Valve has ever been cleaned or replaced? My RX used to have this problem until I replaced the IACV with a new one. I had tried cleaning the original one several times, but the results were not satisfactory. The low mileage on your vehicle may be a two-edged sword, possibly indicating a history of short trips with long non-driving intervals between, giving unburned fuel vapors inside the IAC and the Throttle Body to gain a robust coking presence. I also removed and bench-cleaned the Throttle Body on my RX at the same time, and you would not believe all the brown sludge that came out of that thing. Well worth the time and effort, but certainly a weekend project. I installed a new IAC made by Standard Motor, got it from RockAuto. This was about 4 years ago, still runs flawlessly.

rufftimo

OK, two mechanics looked at this and saw my front torque strut engine mount was in bad shape, and thought that was the culprit, but we just replaced that and the hard shift from reverse to drive remains.

Next we'll be draining and replacing the transmission fluid with genuine Toyota T-IV, but I'm doubtful a fluid replacement will fix the problem...

Hoping not to have to replace the transmission on this, it has 230K miles, might not be worth it. :-/