Torque converter help

[Reiki08]

Hey guys im trying to find out wether i need a higher stall converter or lower stall.. i want to make more low end torque. Somewhere around november 2024 i replaced my transmission, with a remaned one. The guy i bought it from gave me a bigger torque converter and im not entirely sure what its stall speed is. Since then i dont feel much torque being made until around 2800 ish rpm. Im not well versed on how torque converters work so id apreciate some advise. My vehicle is a 2005 trailblazer ext 4.2. Bone stock

 

[Mooseman]

The stock 4.2 is not a high torque engine and makes its power higher in the RPM band. If your rebuilder didn't know and put a "regular" truck torque converter, the stall speed is lower on those and will make your TB more sluggish. Stock, the 4.2 has a higher stall torque converter. It's even used by some that have the lower stall TC as a cheap upgrade.

If you want to find out what your torque converter's stall speed is, do this in an empty parking lot. You hold the brake HARD, put in drive, and at the same time as holding the brake, push the accelerator to the floor. Watch your RPM where it tops out. Only do this for max. 5 seconds. I can try mine later when I get home to see what it is stock but from I have been reading, it should be around 1800-2100 RPM.

If you or your rebuilder happens to know what code was on your TC, VJCX is for the 4.2, TMBX is for the 5.3, which has a stall of about 1600. The 4.2 TC has a 500 RPM higher stall. If he gave you a physically "bigger" converter, you likely got the lower stall unit as the 4.2 one is smaller.

 

[Reiki08]

Oh ok so i did the test and it topped out at about 1700 rpms. Does that mean i should look for the stock torque converter for the tb?

 

[Mooseman]

It would help with that sluggishness you're feeling. However, I don't know how much extra oomph you're looking for. If you just want it back the way it was originally, then the stock TC will work. If you want a little more, then something in the 2500 RPM would be a nice bump but would cost more for an aftermarket TC.