Lex,
I was thinking about our transmissions,and my thought was,theese tranies are electronic controled (I dont think their is any vacuum source for shifts etc.)Any way,Cant shift control (how and when it shifts) be controled by going into the systems computer and changing the patern? Say maybe by a lexus dealer? And i dont mean a re-flash,I cleared mine with my hand held scaner,and the shift from 1st to second was real sloppy for a while.Would just like your,or anyone eleses input on this. Maybe some how increase the line pressure?

 

First time I heard someone suggest this on an RX300.

I am not aware that Lexus can do anything offhand nor anyone else specifically that I know of out there that can modify this electronically for our vehicles in a custom manner, though it certainly is possible. A big issue here is also the relationship between having set shifts points and the adpative learning of our difficult, but not impossible, to crack ECU.

What I have always done is just add some ATF to the equation and of course the pressure is increased. I have tried leaving it at the two hot marks on the dipstick and the acceleration and shifting were always sloppy by my count. For most of my vehicle's time with me (I am the 2nd owner), I have kept the transmission fluid level at the point where it says IV on the dipstick and the shifts were quite good along with the acceleration, though with the recent modifications I have, this has been noticeably improved (and I have the fluid at the same level at the IV mark). What I am going to see after my 1000 miles of wearing in are done is to see how the adaptive learning of the ECU fares with regard to the mechanical upgrades to my transmission.

 

Thank you for getting back to me so fast, as for your up-grades I dont think it should be a problem for your ecm. Our vehicles use the same computer for the engine,and trans right? Some makes,such as Chrysler used a seperate ecm for trans.

 

The manufacturer has to keep the costs down, but also there is a bigger factor of "target customer base (and their profile)". Talking about transmission, I have not seen in RX300 owners manual, how to check transmission fluid level. If you look at Lexus business model, it seems as it is provide customer an elite "green and comfort biased" vehicle, which they can depend upon and also provide above average customer service level (at cost to the owner), where their mobility is not impacted by the time in workshop. It is not performance biased, although at times Lexus has forayed (seems like half hartedly and pulled their punches back) in the performance focused area.

Other than race cars, the vehicles are tuned by manufacturer, to target the above mentioned particular market segment. [imho the adaptability is to make it yet more "green" ... that is the way it always seems to favor]. If there are enough customers/interest some one cracks the eprom code and offers the modified stuff to the special interest group. If you are hoping some one would do it for Lexus and specially RX, don't hold your breath as the opportunity cost for other line of vehicles is more attractive.

The closest any manufacturer has come to allow electronic tweaking has been "Idrive" by BMW. Sweet idea from engineering point of view, but it has overwhelmed a typical customer in the target customer segment [although the performance is hyped to the nth degree, 99.99% of drivers I see on road hardly ever push what ever vehicle they drive to its limit ... if any times it happens, it is when something unexpected happen (never done intentionally by driver).

Salim

On second thought, it is good that drivers dont push their vehicle to their performance limit on public streets.

 

Wow!!,I think what you said is,no one in the performance dept. is going to bother to offer us an alternative eletronicly Right? I had a 2003 Chevy cavalier I worked on once,and the guy put a shift point changer thing he bought from some where.and one end pluged into the torq converter plug,the other end pluged into the original wiring harness.Then their was a black box in the middle of all this that had an adjustment screw on it to modify how hard you wanted the shifts to be.(probably just modified the line pressure mostly)To bad we cant get a plug and play like this for ours.He said it worked great at first,then he played with it too much and couldnt get it the way he wanted after that.(dont underestimate the obd2 system,it is pretty advanced)the computer probably started to compensate for this gadget he put on.

 

Ours is run out of the main ECM, but there are some electronics in the transmission itself related to sensors/solenoids. I am not sure about the Chrysler, but there are some vehicles that have a TCM (Transmission Control Module). I know Mercedes have a similar adaptive transmission. I believe the ES350 has a TCM.

 

There is a much larger community interested in tweaking cavalier or other chevy or even other manufacturers ,, when it comes to Lexus owners, the number is too little.

Example ... SRT offers an intake for GS and one has to cut and solder a wire to the ecu [my assumption here ... it was easier to fool the ecu instead of re-mapping it]. Just this change gave cold feet to GS owners who were looking for boost.

If you scour the net for accessories (not even performance enhancement options) for RX, there is not too much being offered ... reason once again is the market is too small ... compare it with civics, imprezas etc.

My position has been, you are better off (cheaper and options of success are more) working with another vehicle. This kitten can not be transformed into tiger. Sure you can sharpen the nails, make it purr harsher but that is about it.

Back to your original quest .. why not rove the gear shift selector to control the shift point?

Salim

 

Salimshah,How does that adj. affect the shifting? is it like a detent cable adjustment?