Last post on Feb 29, 2008 at 1:44 PM
You are in the Lexus RX 300/330/350
What is this discussion about?
Lexus RX 330, Lexus GX 470, SUV
#3 of 10 Annoying Hesitation / Downshifting
Jul 22, 2006 (11:24 am)
I love my RX, but believe the transmission doesn't reflect the attention one comes to expect from a Lexus product. I've had the same hesitation issue at slow speeds with my 2004 RX with 20K. Even more annoying (to me) is the transmission's desire to downshift/upshift while going up hills. My Dealer tells me its all 'normal' to this vehicle. On the other hand, I drove different Acuras for years and had no similar issues with Honda's Grade Logic transmission. I haven't driven the new 400H, but if I understand the ECV transmission, it probably alleviates or eliminates our complaints -- I'm just not willing to fork out $50K for the fix. In a couple of years I expect Lexus to migrate toward the ECVT in the non-hybrid RX.
#4 of 10 Re: Annoying Hesitation / Downshifting [kmrice2803]
Jul 23, 2006 (12:32 pm)
Even more annoying (to me) is the transmission's desire to downshift/upshift while going up hills.
I have the same annoying problem w/ my GX. Ours is an '04 and has only 4 drive gears. On the GX thread someone w/ an '06 posted that he avoids those surges by driving in 4th .. there's a 5th gear in the later models ... or so I'm told. I haven't seen one myself however. Bart
#5 of 10 Ford's answer....
Oct 17, 2006 (12:38 pm)
Impossible to believe...
Ford has the answer.....!
From the new 2007 Ford Edge PR..
"The electronically shift controlled transmission also features a variable displacement pump, which matches the amount of fluid that gets pushed through the transmission to driver demand, making it more efficient."
At full lift-throttle all of the FWD Toyota/lexus vehicles begin an upshift just as the engine RPM drops to idle. With the engine at idle the upshift will exhaust/use most, or possibly all, of the pressurized ATF.
Now if you happen to re-apply foot pressure to the accelerator pedal just as the upshift begins the engine/transaxle ECU will "know" to delay the onset of engine until the low engine "idle" RPM can build enough ATF pressure to complete the corresponding downshift.
The most obvious answer would be to increase the volume of the fixed volume ATF pump so enough pressure/flow could be provided for two sequential QUICK shifts with the engine at idle. But then most of that added volume would be bypassed, dissapated as heat, as the engine RPM rises above idle.
Ford's answer, apparently, is to have a variable displacement ATF pump so it can be switched to high volume when quick/SOLID shifting is required with the engine at idle. Makes me wonder if that allowed them to eliminate the ATF pressure bypass relief spring/valve also.
That would REALLY increase transaxle efficiency.
A second option would havre been to have an ATF pressure storage accumulator (like the ABS pumpmotor asembly). But putting one of those in an already "crowded" six-speed transaxle is probably out of the question.
Anyone know if any of the newer Toyota/Lexus transaxles have either? Absent one or the other the delay/hesitation issue will undoubtedly continue.
#6 of 10 Hesitation
Mar 08, 2007 (3:09 pm)
I have a 2005 RX330 with the same hesitation when accelerating at low speeds as does a friend. You might want to know the problem has made the February 2007 issue of Kiplinger's Personal Finance magazine.
#7 of 10 Re: Hesitation [jim2244]
Mar 08, 2007 (4:03 pm)
Another owner and myself are curious if the low-speed hesitation you are experiencing is related to tire slippage/VSC-Traction Control engagement when accelerating.
Can you give more details about yours and your friend's experience?
#8 of 10 Re: Hesitation [la4mead]
Mar 09, 2007 (12:05 pm)
I'm not sure if the hesitation I feel is due to slippage or some other problem, but I've only noticed it at low speeds, I think mostly between about 20 and 35.
I just asked my friend if he had a hesitation problem and he said yes and was going to have it looked at with his next scheduled maintenance, which is what I planned to do.
Also, I stopped to get gas this morning and asked a woman with an RX 330 at the pump next to me if she had noticed a hesitation problem. She said yes and that her husband said it was because the car was underpowered. I don't think that's it. I'm guessing its the transmission, but that's just a guess.
My primary concern is that it could be dangerous. If you need to get out of the way of an accident and an idiot, the hesitation could be a real problem.
#9 of 10 Re: Hesitation [jim2244]
Jan 17, 2008 (9:38 pm)
You may be interested in the fact that Toyota Avalon has this same problem. Toyota came out with a TSB that will correct the hesitation problem. If I get enough replies I will find the TSB number and post it and you can inform your service mgr.
As far as I know Lexus and Avalon transmissions are the same.
#10 of 10 Found it..!!
Feb 29, 2008 (1:44 pm)
1. The act of doing away with or the state of being done away with; annulment.
2. Abolishment of slavery.
Following statement taken from Lexus NCF, New Car Features, for the '99 RX300.
1. Direct Clutch Fluid Pressure Control
Direct fluid pressure control using linear solenoids is adopted for fluid pressure control of B1 and C2 for engagement/release upon shifting between the first and second speeds and between the second and third speeds.
The output pressures from linear solenoids SL1 and SL2 are led to B1 and C2 control valves for optimum control of each clutch pressure. As a result, the automatic transmission size is reduced by accumulator abolition and fine fluid pressure control not possible with clutch fluid pressure control using accumulators.
"..the automatic transmission size is reduced by accumulator abolition..."
Fluid pressure accumulators are often used to sustain/maintain fluid pressures for the brief periods it takes for the hydraulic pump speed to rise to the required flow level.
Eliminating the accumulator was undoubtedly one of the methods used to make room for fitting more robust components into an otherwise light duty Camry transaxle that was now to be used to haul around a much bigger and heavier vehicle.
Premature transaxle failures for '99 & '00 RX300's.....
Prematurely burned ATF fluid for the '01 to '03 RX300 series...
1-2 second downshift delay/hesitation throughout the Toyota/Lexus FWD and F/AWD fleet due to DBW being used to delay the onset of engine torque until the gear type ATF pump could pump enough fluid with the engine at idle to bring the pressure back up to snuff....
Engine flare during 3-4 upshifts...
All traceable to one simple engineering mistake made during the design phase for the RX300.