I am wondering if it is possible to swap a is350 motor into a is250 manual transmission?
Is it worth it and would it be a direct bolt on to transmission do apologize for dumb questions but am new to the Lexus it is my first lexus car and well I have an is250 6mt but prefer the is350 motor and power vs the is250 but don't like the automatic transmission on the is350

 

 

It can and has been done. The physical aspect is nuts and bolts. It's the electronics and their associated wiring from 250M to 350A and the 350's ECM that will bog you down. If you're not up for opening wiring harnesses and reading schematics, just go buy another car.

A forum moderator has done this. Search as suggested above!

 

Mechanically, it's bolt-in. You just need to get the appropriate parts (engine, harness, fuel lines, hoses, etc.). The clutch requires upgrading as well (the stock clutch is good for approx. 250 ft-lbf of torque, the 2GR-FSE is above that). There are modifications required to the wiring harness to match up with the transmission, and the body-side ECU connectors need to be repinned. There is a bit of trickiness required to get things to work correctly with the clutch pedal and starting as well (the clutch pedal starts the car, but also tells the ECU that you are in neutral which kills the engine response after a shift for approximately 1-2 seconds; you need to split these two functionalities by rewiring one of the body harness pins). Additionally, with the IS350 ECU, you need to be able to put the car into "P" in order to do things like zero-point calibration, etc. (the MT cars use the park brake), and so I would suggest adding a method to do that; I ended up putting in a "diagnostic connector" in the ECU box to allow it to be put into park. You can leave it in neutral if you want normally, but if you do, you won't be able to use cruise control. Repinning the clutch cruise control cancel switch to put the computer into "D" will allow correct cruise control functionality.

Note that all of this assumes you can get the engine ECU reprogrammed to "ignore" or at least almost ignore the automatic transmission issues. That's another whole thing.

(This post contains more information than I've ever given about how to make the electronics work, I was in a good mood today.)

Jeff

 

^^^^Surprised you didn't point the OP to your thread:

https://www.clublexus.com/forums/bui...is350-6mt.html

Lou