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Old 02-14-2010, 07:58 PM   #1
Old Yeller 1970
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4L80E shifts hard, your thoughts on the fix?

I have a '06 3500 van with 60k mi on it. Recently it's begun shifting hard and the check engine light came on. I took it by Autozone and found a P0894 code.
The printout reads: Transmission component slipping. The ECM has detected that the TCC slip speed is greater then expected. Probable cause.
1. Low transmission fluid level (It's OK)
2. Contaminated transmission fluid (I bought a filter and 8 quarts of Dexron IV)
3. Failed TCC soleniod. (Neither the Autozone guys or myself -till I got home- knew what a TCC (Torque Converter Clutch) solenoid was so I didn't get one yet)
4. Poor electrical connection. (I crawled under and everything appears to connected OK)

Since TCC solenoids are relatively cheap, esp compared to the cost of trany fluid, I figure to put one in. Under normal circumstances the fluid should be replaced every 100k mi and I doubt if it's contaminated enough to cause the problems. But I would welcome others experiences.

If I buy a new TCC solenoid, will it be obvious where the original one is once the pan is dropped or am I going to have to dig for it?
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Old 02-14-2010, 08:35 PM   #2
clinebarger
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Re: 4L80E shifts hard, your thoughts on the fix?

Without a good scan tool it will be hard to proporly dianose this. But if you want to throw parts at it, replace the TCC PWM solinoid first and get back to me.




Possible causes

A TFP manual valve position switch malfunction can set DTC P0894.
A mechanical failure of the shift solenoids or TCC PWM solenoid valve can set DTC P0894.
Internal transmission failures can result in a DTC P0894.
Sticking or contaminated shift valves may cause intermittent slipping in D4.
DTC P0894 defaults to an elevated line pressure condition which may result in partial TCC apply. This may produce an idle surge that could stall the engine.





Locations

22a - Automatic Transmission (AT) Input (Shaft) Speed Sensor (ISS) Assembly
22b - Automatic Transmission (AT) Output (Shaft) Speed Sensor (OSS) Assembly
34 - Automatic Transmission Fluid Temperature (TFT) Sensor
40 - Automatic Transmission Fluid Pressure (TFP) Manual Valve Position Switch
311 - 2-3 Shift Solenoid (SS) Valve Assembly
313 - 1-2 Shift Solenoid (SS) Valve Assembly
320 - Pressure Control (PC) Solenoid Valve Assembly
323 - Torque Converter Clutch Pulse Width Modulation (TCC PWM) Solenoid Valve Assembly
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Old 02-14-2010, 08:36 PM   #3
cableguy0
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Re: 4L80E shifts hard, your thoughts on the fix?

The transmission should be flushed every 30k miles. Theres almost no vehicle around that qualifies for normal conditions. Most driving conditions are severe.The firs thing to do is have the transmission flushed. What does the fluid look like? Is it brown? Does it smell burnt. The tcc selenoid is not the only thing that will cause that code. It could be a bad shift selenoid,stuck shift valve,burnt up lockup clutches.The hard shifts are because of the code. Once that fault occured and set the code the computer maxes out the line pressure so you dont hurt the transmission. You also need to unplug the electrical connector that goes into the tranny and make sure nothing is corroded or burnt. Most of the electrics are in the pan so you cant see them. You really need someone with diagnostic ability to look at it before you piss away a bunch of money throwing parts at it.
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Old 02-14-2010, 09:55 PM   #4
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Re: 4L80E shifts hard, your thoughts on the fix?

Quote:
Originally Posted by clinebarger View Post
Without a good scan tool it will be hard to proporly dianose this.
I take it the Autozone scanner is not a good scan tool? And big thanks for the diagram and pointing out the other possible causes.

Quote:
Originally Posted by cableguy0 View Post
The transmission should be flushed every 30k miles. Theres almost no vehicle around that qualifies for normal conditions. Most driving conditions are severe.The firs thing to do is have the transmission flushed. What does the fluid look like? Is it brown? Does it smell burnt. The tcc selenoid is not the only thing that will cause that code. It could be a bad shift selenoid,stuck shift valve,burnt up lockup clutches.The hard shifts are because of the code. Once that fault occured and set the code the computer maxes out the line pressure so you dont hurt the transmission. You also need to unplug the electrical connector that goes into the tranny and make sure nothing is corroded or burnt. Most of the electrics are in the pan so you cant see them. You really need someone with diagnostic ability to look at it before you piss away a bunch of money throwing parts at it.
Let me make sure I have this straight. If the fluid is dirty, does the vehicle detect this (like it does with engine oil) and set the fault code and max out the line pressure? And if this is the case, then is it simply a matter of replacing the fluid, resetting the computer to clear out the fault and it will start shifting normally?

To answer your question, there is no burnt smell. It's not brown but it is a slightly darker shade of red than new fluid. I do plan on replacing the fluid for sure but if its probable that the TCC solenoid is bad I'd rather replace it for $20 than have to come back and pull the pan off a second time. My manual says that under severe conditions the fluid should be replaced every 50k mi so you have a good point about not getting close to 100k before a change is necessary.
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Old 02-14-2010, 10:04 PM   #5
cableguy0
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Re: 4L80E shifts hard, your thoughts on the fix?

No,the vehicle does not detect dirty fluid. It is the dirty fluid and the crap in it that will cause the shift valves or selenoids to stick. The thing autozone has is not a scanner its merely a code reader. You need to be able to get into the systems and verify components are working the code reader cannot do that. The dirty fluid is a possible cause but not really the direct cause. Theres still a component fault to throw the code. The question is which component isnt working properly which is where the dianostics come in. Pretty much everything that can cause that code is accessed by dropping the transmission pan.
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Old 03-02-2010, 01:16 PM   #6
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Re: 4L80E shifts hard, your thoughts on the fix?

I changed out the transmission fluid yesterday. I had a TCC solenoid on hand which turned out to be the wrong one. I bench tested the original. It was working fine and I left it in. Once the old fluid was out I could see how dirty it was which was pretty bad. After putting in the new fluid the tranny shifts fine. Thanks for all the advice.
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