Nice work Jeff! I stand corrected! I had no idea our cars "could" be capable of that.:eek2:

I looks like Lexus limits the top speed by limiting RPM in top gear.
5th gear with stock gearing = 149mph at 4650rpm.
The interesting thing is that stock gearing at redline (6300rpm) in 4th gear = 153mph :uh:
With the Supra 3.769 ratio the electronic limit of 4650rpm = 125mph.
Redline in 4th = 127mph.

My LS400 drops from an indicated ~6200rpm to 5000-5100rpm 1st to 2nd shift.

If your torque converter is staying locked that should not be due to the torque converter itself but rather the signal to lock/unlock from the ECU.

If this is happening it would not cause (in and of itself) other tranny problems.

Another thought is how quickly your transmission shifts. Stock shifting is slow. During this transition there is load applied and by the time the shift is complete the resulting revs would probably be higher that a quicker shift that pulls down on the engine more quickly. Cars with the PI torque converter tend to shift more quickly. Again, something is going on here.

...what should I do J?

-I can't bring it to the dealership (who supposedly knows all about Lexus vehicles) because they would say they can't "possibly" diagnose the car due to the modifications.

-I cant's bring it to a local shop because they may not know how to fix this particular issue due to my mods.

This is the annoyance of modding because if an issue should arise it is hard to decipher which mod is causing the problem.:sad:

I would PM other PI converter owners and ask them to test their RPM at shift points. It may be a common instance when running the converter and or converter 3.769 gearing combo. It may not be anything worth worrying about. BTW, have you been to a track or done any measured runs, 0-60 and or 1/4 mile?

No, the nearest track is about 2-3 hours away.:thumbdn: Also, it wouldn't even be fun because I NEED wider, stickier rears for traction in order to obtain proper figures of the car's performance.

I contacted Derrick from D2 Autosport and I am looking into the Forgestar F05's (19X8.5 front / 19X10 rear) w/Toyo Proxes T1R's (275's in the rear). Those wheels are only 22.5lbs each!:eek2: A net savings of 7lbs per corner from my old (now sold) cast aluminum 19's.:thumbup:

I will try to PM a couple of members with my setup as you suggested. Thanks.:)

Usually you can tell when you in 5th gear and you are crusing when you hit the gas just a tad bit harder it feels like youre in 5th gear driving a manual tranny car, thats the best way i can explain it to you. Like it has no give when you beraly tap the gas without converter unlocking in O/D you feel sorta joult from the drivetrain it might be hard to feel in a smooth car like a GS though. you can also watch it shift when you drive it, watch rpm drop from 1st-2ndto 3r4d-4th and then pay attention when you get to 5th watch it shift and then keep an eye on it and you should see rpm drop like another 200-400rpm after it shifts into 5th that means converter just locked, if it dosent do that its either
a. not locking at all
b. locked all the time
your Trans Ecu could be bad in a way and you might not be getting a CEL, you wont always get a CEL if something is wrong, i have seen cars run missing 2 cylenders and cel wont come on.