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05 chevy Avalanch transmission trouble.

David Abla

By David Abla
in Ask A GM Technician

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David Abla New Member

David Abla

Posted
Posted

 my transmission when I disconnect the cooler tube on the top of the radiator to go to the transmission no transmission fluid comes out and it's showing a code P O 894 I just recently had the transmission rebuilt it's got about a hundred sixty thousand miles on it when I had the transmission rebuilt it had 130000

David Abla New Member

David Abla

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1 hour ago, davester said:

when did you disconnect it?  If it was sitting for awhile, the fluid could have drained back into  the transmission.

When the engine is idling with the transmission line that comes out of the upper radiator cooler port, disconected there's no fluid draining out into my bucket, the fluid level on the dipstick shows the fluid level is alittle high , so shouldnt some fluid come out.?

davester Senior Enthusiast

davester

Posted
Posted

Do you know which transmission it has?  It's likely either the 4l60e or 4l80e.  If it's the 4l80e (and probably also for the 4l60e, but I'm not 100% sure of it), transmission fluid (or engine oil if you disconnected the wrong tube) should be pumping out of either the line or the radiator fitting it goes in.

 

I would suggest first disconnecting the other line, and see if fluid comes out of that one with the engine running. 

 

If it does, then the radiator is plugged (for transmission fluid, as I think you would have noticed if it was running out of the radiator when you did your first run).

If it doesn't, then I would disconnect the lines at the transmission, and blow through them, to see if either of them are plugged.

 

If plugged, then I would just replace them both.

If not plugged, and you run the engine and fluid doesn't come out of the transmission ports, then something is wrong inside the transmission.

 

And the P0894 code, which indicates the clutches aren't locking up like they are supposed to in the transmission, could be due to low fluid pressure (ie, a failing oil pump in the transmission)...

 

This is all based off what I know of the 4l80e, but I expect the 4l60e to be very similar (in that it always pumps fluid through the oil cooler).

carkhz316 Enthusiast

carkhz316

Posted
Posted

OP, you have a 4L60e. The trans component slippage code can be caused by a number of things. Proper test drive and diagnosis is key to figuring this out. While the lack of fluid flow out the cooler line is disconcerting, I would ignore that for now, as it's only potentially a symptom, and the cause is still going to be within the transmission. What does your truck do from a driveability standpoint? Is it slipping or mis-shifting?

David Abla New Member

David Abla

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3 hours ago, carkhz316 said:

OP, you have a 4L60e. The trans component slippage code can be caused by a number of things. Proper test drive and diagnosis is key to figuring this out. While the lack of fluid flow out the cooler line is disconcerting, I would ignore that for now, as it's only potentially a symptom, and the cause is still going to be within the transmission. What does your truck do from a driveability standpoint? Is it slipping or mis-shifting?

I dont notice any slipping but it shift hard, by that i mean the rpm get high and then kinda jerks into the next gear

Doug_Scott Senior Enthusiast

Doug_Scott

Posted
Posted

Does it have all 4 gears when driving?  Are you only getting one code?  I would have expected it to throw a code for line pressure or a code for something else in addition to the meaningless generic code it is giving on its own.

 

Generally a hard shift is a sign of high line pressure, but, slippage is a sign of low line pressure.  No fluid out of the cooler line at radiator or out of radiator either means the trans cooler in the radiator is plugged, or you have low line pressure.  As already suggested disconnect the other line at radiator, and you may want to reconnect the upper line first.  You may want to have someone else start the truck while you try to catch the oil.  Be prepared for a mess if it does come out.  It may not be a lot of pressure, but it will make up for that in volume.

 

Check the fluid for colour and smell.  If it is slipping, the fluid will smell.  If you are not sure, ask your wife to smell it.  I found out years ago it is not funny to wipe your finger under their nose after rebuilding a burnt black automatic transmission.

 

Take the truck out and count the shifts, you should have 3 shifts plus the lockup after 4th gear.  30, 000 miles isn't recently.

carkhz316 Enthusiast

carkhz316

Posted
Posted

The harsh shifts are due to to PCM commanding maximum line pressure (limp mode of sorts) due to the slippage code, in an effort to mitigate further slippage. This, again, is another a symptom, so we need to find why the PCM is detecting the error. Also, the PCM may inhibit 4th gear and/or TCC lockup during this time too. 

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