hard shift when cold or tow/haul mode

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hard shift when cold or tow/haul mode

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Chevrolet >> Chevy Trucks, Vans & SUV's >> Silverado >> hard shift when cold or tow/haul mode

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hard shift when cold or tow/haul mode - 4/21/2008 3:30:33 PM

mroakdale

Posts: 4
Joined: 3/2/2008
Status: offline

Hey guys this is my first post so bear with me please. I have a 1999 siverado with a 5.3 . it shifts hard 1st to 2nd when it is cold (live in minnesota) when it warms up it shifts fine. if I put it in tow/haul mode it realy ****s hard when cold. I changed filter and fluid no help. truck only has 44,000 miles on it.

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RE: hard shift when cold or tow/haul mode - 4/21/2008 4:29:12 PM

northey87

Posts: 847
Joined: 10/17/2007
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Welcome to the forum!!! The hard shifting probably because the when the fluid is cold its like molasis in an igloo.

And when its in tow mode it shifts harder/faster so the truck doesn't lose momentium while towing something heavy.

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RE: hard shift when cold or tow/haul mode - 4/21/2008 5:07:22 PM

mroakdale

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Joined: 3/2/2008
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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

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RE: hard shift when cold or tow/haul mode - 4/21/2008 8:52:05 PM

ehhget

Posts: 349
Joined: 1/22/2008
Status: offline

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.

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RE: hard shift when cold or tow/haul mode - 4/22/2008 7:19:21 AM

bad2006z71

Posts: 81
Joined: 2/8/2008
Status: offline

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.

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RE: hard shift when cold or tow/haul mode - 4/22/2008 8:30:39 AM

ZX1100F1

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Joined: 8/1/2006
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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.

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Dave

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RE: hard shift when cold or tow/haul mode - 4/23/2008 1:40:04 PM

tecate1987

Posts: 2
Joined: 3/23/2008
Status: offline

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.??

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RE: hard shift when cold or tow/haul mode - 4/23/2008 2:51:33 PM

ZX1100F1

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Joined: 8/1/2006
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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.

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RE: hard shift when cold or tow/haul mode - 4/23/2008 6:33:39 PM

tecate1987

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Joined: 3/23/2008
Status: offline

thanks ZX1100F1, 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.

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RE: hard shift when cold or tow/haul mode - 4/24/2008 8:56:41 AM

ZX1100F1

Posts: 2429
Joined: 8/1/2006
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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.

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Dave

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