I can see why the TCs are doing so much for GS400, factory is not even close to peak torque and that is where we should be coming from. It looks as if even the 2850 TC adds just a little more over the 2800 stall. Each mfg has their own design on torque multi applied. Each one seems to be different, correct me if I am wrong.

 

The only aftermarket torque converter for the GS4 is from Precision Industries as far as I know. SRT and RMM sell the PI one.

As far as 2800 vs. 2850 I doubt most people could notice. I have 2800 and love it. Makes a huge difference. And while I doubt I'd notice a switch to 2850, the higher the stall the less driveable ultimately. Not saying 2850 is any different in drivability over 2800, but 3200 for example would be pretty bad to drive (gear hunting, revs going up and down a lot) in normal driving. Maybe fun on the track though.

 

yeah i don't think people can really tell the difference between the different stall speed. but either way on the v8 it's going to help a lot for sure

 

2800 vs 2850,.......other factors affect your actual stall speed as well. ie. tranny fluid, condition of brakes,....traction coefficient of road or track......

outside of Lexus and Precision Industries, I would believe that all of the torque converter manufacturers are using the same basic design. It's simply a matter of the pitch/spacing of the two halves inside the converter. (I believe, but I could be wrong) The quality of the parts inside and welding are huge details for a TC as well.