Is the manual tranny really worth that much to you? I would think that it would be easier to electronically "hack" the auto tranny to make it work more like a manual than to replace it with a manual. It is a good tranny. Lexus just made some poor software choices.

 

I wouldn't waste my time with the 250 gearbox. The Getrag 233 will likely need an adapter plate since it doesn't have a separate bell housing (it's integral to the front of the gearbox.)

You may also have some pretty heavy duty fabrication in terms of getting the shifter located in the cabin. Either you'll be rebuilding the shifter mount that bolts to the aft section of the gearbox, or you'll be doing something really challenging to the body floor pan. As low as the shifter height is on the 233 and as high as the console is on the 350, you'll have quite a project getting the shifter where you want it.

Add to that a custom driveshaft. If you are really lucky, you'll be able to use the front section from a Supra and graft it to the rear section from the 350. The four bolt yoke on the Getrag isn't going to play nicely with the three bolt yoke on the IS especially since the Lexus yoke has a donut on both ends and the Supra only has a donut in the rear.

Have you thought about gearing yet? Looks like it will be pretty quick, but not so great on cruise or top end.

 

I want that spreadsheet!

 

It looks like the Getrag gearing in an IS 350 would not be particularly optimum for 0-60 or 1/4 mile times since each would require an extra gear shift. Not that I think 0-60 or 1/4 mile times are all that important ... I'm just sayin'.

 

However, it looks like the 5th and 6th gear IS 350 Getrag "RPM AT MPH" chart is in error.

 

This begs a question for all of you who've run your 350 to the limiter: it looks like you'd hit the limiter right at the tail end of the powerband in 6th. Does it hit you like a wall like it does, in say, the m5, or the e55/e63?

 

I'll let you fix it on your copy. It's fixed here now.

 

Thanks for sending it! BTW, what RPM is the rev limitter set to?

 

Not sure if this is what you're looking for, but I hit the limiter at 6700 RPM during dyno runs.

Javier

 

No. I've hit the top speed governor in 6th, and you just stop accelerating. It's not extreme at all. However, I'm sure it has to do with the fact that you're not actually hitting the RPM limiter, just the electronically governed top speed.

Javier

 

It should be easier take a 6speed IS250 and do an engine swap.
I am sure you will lose alot of feature and lot of custom work.

It will be easier to try to try to get some extra HP from IS250 than making a 6speed IS350.

Give tuner sometime, the car is still too new for tuners to come up with reliable packages.

Took tuner good 4 years after the lauch of E46 M3 to come up with SC kits, give tuner some time.

 

Ive searched and couldnt find anything is there anyone that makes an aftermarket clutch for the 250 yet???

 

The clutch on the 250 MT is bad. I'll let you know when mine goes out.

I would agree that it's, in theory, easier to put a 350 engine in a 250MT. The stock clutch would need to be replaced with an aftermarket sooner than usual but is expected.

I put on over 40k a year on my 250 mt, so in 5 years I'd seriously do an engine swap. But doing it on a newer car, we'll I'd put that money towards a true track car like an elise, evo, sti, s2000. Cool that someone is doing it though. Good luck

 

i would just drop a supra engine with tranny and call it a day..

 

I'm with you on that one!!!