Need help with this Lexus and how to set the Kick down on the trans ?

that is a good car so I would let a shop do a Diag correctly

you should use the highest gear possible to allow over drive to kick in, other gears will slow and limit the speed you can drive ,and stress the tranny

5speed manual transmission.
jumps to neutral? moving fast, slow, hills ,turns, down hill, where>?
my guess. is:
1: bad engine/tranny mounts
2: bad shift linkage.
3: bad trans.

what makes you thing the tires/wheels tighten (felt by hand off ground?)
my guess , you meant it seems. like???
1: lost engine power?
2: transmission not up shifting?

is this a auto A/T or manual M/T tranny,
if A/T , you need to look at the engine RPM when you lose
power (acceleration on demand)

RPM rises, car dont move faster ,this is tranny slip.
RPM fails to increase, and speed, up hills. this is called lost engine power.
lost engine power can be caused by , bad spark (tuneups skipped?)
or weak fueling.
weak fueling too can be cause by skipping the fuel filter step in the tune up list.

Doesn´t seems like a mechanical failure. Check wiring and connectors related to the tranny.

sounds like maf fault
if a plastic accelerator the pedal sensor
auto kick down solenoid

Sounds like an electrical or computer issue I would take it back to who ever put the tranny in and have them check it out. It could be 1000 things, and may not be related to the tranny replacement at all.

Btw, I’m available to help over the phone in case u need at https://www.6ya.com/expert/sean_54c3a3dc48a7773c

have the same problem with 1999 mazda pickup try flushing the tranny and put in a new filter replace one quart of tranny fluid with some lucas trans fix and see if this helps it any, was told the tranny will need to be rebuilt.

tranny shift cable thats hook up below the throttle cable on carb needs adjusted

try changing the tranny fluid