jet0924

Just dropped an lq9 in my 2000 4th gen w/4l60e and the trans will not shift under full throttle. Simply bounces off the Rev. Limiter. Also my torque converter is making a rattling sound that got significantly worse after dropping the 6.0 in and I'm having power issues at highway speeds under light throttle. For instance running 65mph the tach will sometimes climb up but the car doesn't accelerate. But when I give it more gas it stops revving and power is restored. Also going downhill, without giving any throttle, the rpms should hold, instead it is occasionally dropping down to an idle as if I'm in neutral​...I think it's a broken converter..but I'd like other opinions before I order another.

PBA

If the 2-3 shift is the one that is happening, (adding more power will do this) then the 3-4 clutch setup is most likely the problem here, no enough capacity. Whose torque converter are you using here? Was the transmission working ok before? Torque converters do not let it go into a "false neutral". The overrun sprag/clutch setup sounds like the problem here. The rpm's going up and down is the torque converter clutch coming on and off. Need more information? How many miles on the transmission? Etc.

jet0924

it was happening in all shifts, trans only had 4k miles on rebuild. Everything worked fine with the 5.3. UPDATE. The torque converter was a major issue to say the least. It completely let go a day after I pised this thread. New one will be in on Friday and I'll be able to update further. Went with a circle d pro series with 3200 stall. The old torque converter was simply a stock converter. Had planned on swapping it with the engine swap but the tranny shop gave me the wrong converter unfortunately. Hopefully this will fix my issues. I'll update you as soon as possible. Thanks for your input! Also, when you say not enough capacity, are you referring to the fluid capacity problem?

wht/73

Make sure to flush everything out BEFORE you put the converter in.
Good luck.