mroakdale

The hard shift is harsher then just being thick fluid in tow /haul it feels like it is slamming into gear, but works ok when warm

ehhget

I dont know about the cold cause I live in Phoenix but mine does shift harder in tow haul but I cant say it slams. I know there is something in the filter area that controls firmness due to the flow of the fluid but I cant remember what it is. Hopefully someone smarter than me will know more.

bad2006z71

Mine doesnt have a "hard" shift actuallly it seems barely noticable that it shifts at all. the tow haul mode is more noticable and i like the way it feels.

i dont know much about transmmisons but from what i have read the 4l60e trans is a weak trans. you might want have a reputable shop look into it.

good luck.

ZX1100F1

There are two possible solutions.
First; have the PCM flashed with updated software that is designed to address this issue, have the dealer reference GM Document ID # 585532 for further reference if needed.

If that doesn't resolve the harsh 1-2 upshifts then have the transmission pressure control selenoid replaced.

tecate1987

chevy truck shifting hard.
I have a 01 silverado 5.3 engine, mine will shift like in tow mode(longer shift points) in the winter time til it warms up.Dont shift hard. In the manual it says its suppose to do this til it warms up. maybe this is what you are talking about.??

ZX1100F1

The cold circuit simply raises the RPM's at each shift slightly to warm the engine faster this reduces emissions and improve heater performance, it should not make the transmission feel as though it is "slamming" gears or otherwise shift objectionably harsh, this feature is also only active when the temperature is 32F or colder.[/b]

tecate1987

thanksZX1100F1, I wasnt sure how he meant it. Along with the cold curcuit,
Mine will also slam if I have been driving for sometime if I hit passing gear hard or going up steep hills where it shifts to passing gear, after that, when I take off from stops it will slam into 2 and hard to 3rd just normal take off. Once I shut the ignition off and restart it, its usually fine. Sometimes the check engine light comes on, sometimes it dont. But that usually stays on til cleared. I get code P01870.

ZX1100F1

If you are getting DTC P1870 this indicates a slip condition inside the transmission which can be casued by numorous things such as:
Slipping band or clutch.
Incorrect fluid level.
Contaminated fluid.
Torque converter clutch malfunction.
A faulty converter clutch valve.
A faulty turbine shaft o-ring.
A faulty TCC or PWM selenoid.