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Chevy 4l80 lockup won't stay locked #5421726 05/05/20 02:17 PM
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Weldlife207 Offline OP
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I have a 2004 chevy 2500hd 6.0 with a 4l80. Just rebuilt the transmission. New tcc solenoid and torque converter. The truck runs ok till it warms. Then when you get to 50 it will lockup 3 or 4 seconds later it will come unlocked. Sometimes it will lock again for a few seconds but most times it won't at all. When on the interstate it gets to almost 200 degrees and gets worse. Usually it runs like 140 degrees. On the last 3 hr drive the truck tripped the check engine light ode p0894. I don't know what to do I've replaced everything except the pcm. Someone must have had the same issue and figured it out. Please help i don't know what else to do.

Re: Chevy 4l80 lockup won't stay locked [Re: Weldlife207] #5421776 05/05/20 03:23 PM
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PontiacHO Offline
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Have you tried adjusting the brake light switch down at the pedal? There was a time when a maladjusted switch would cancel the torque converter clutch. Check all the connectors everywhere. Almost sounds like it’s slipping if you’re getting that particular code. Did you blow out the valve body and all the passages in the case?

Re: Chevy 4l80 lockup won't stay locked [Re: Weldlife207] #5421781 05/05/20 03:32 PM
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supton Online Content
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Old and worn out? The TC that is. Clinebarger would know the issue is...

Until fixed I'd shift out of OD and that should keep it much cooler.

Last edited by supton; 05/05/20 03:32 PM.

2011 Toyota Camry, base, 2.5L/6MT, 205k, hers
2010 Toyota Tundra DC, 4.6L/6AT, 159k, ours
1999 Toyota Camry LE, 2.2L/4AT, 225k, his
Re: Chevy 4l80 lockup won't stay locked [Re: Weldlife207] #5421815 05/05/20 04:09 PM
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zrxkawboy Offline
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Did the problem show up after the rebuild and new converter, or has it been there all along?


"Think of all the Ford owners who will someday want an automobile." John Dodge

Re: Chevy 4l80 lockup won't stay locked [Re: Weldlife207] #5421837 05/05/20 04:44 PM
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mk378 Offline
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When the converter locks the output rpm should exactly proportion the engine rpm, if it does not you get that code. Are all speed sensors working?

Re: Chevy 4l80 lockup won't stay locked [Re: Weldlife207] #5421858 05/05/20 05:04 PM
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Strokenmerc Offline
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I had a OD lockup issue with a '04 4L80 in a 2500 also. Mine would lockup for a few miles then unlock and stay unlocked unless you stopped and cycled the ignition. Every so often I would get random misfire codes but only at highway speeds after the OD kicked out. I will save the aggravating part and just say the issue was the ecu would not keep the CKP Variation Learn. I could relearn the crank position and it would stay locked until you cycled the power. Then it would unlock just like before. Eventually replaced the ecu and did a final CKP Variation Learn and no more problems.

Doesn't sound exactly the same but it's not always the part acting up that is the root cause.


2018 Kia Sportage
2011 Chevrolet Cruze
2004 Silverado 2500HD
2003 Chevrolet Trailblazer
2001 Chevrolet Camaro SS
1999 Toyota Tacoma
Re: Chevy 4l80 lockup won't stay locked [Re: Weldlife207] #5421907 05/05/20 06:00 PM
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nascarnation Offline
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Is the lu solenoid doing as it is commanded? Or is there a hydraulic/mechanical issue somewhere?
A P0894 indicates the lu solenoid is commanded on but there is slip between the flexplate and the converter output.

Re: Chevy 4l80 lockup won't stay locked [Re: supton] #5421976 05/05/20 07:37 PM
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supton Online Content
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Originally Posted by supton
Old and worn out? The TC that is. Clinebarger would know the issue is...

Until fixed I'd shift out of OD and that should keep it much cooler.

Bah, I see now that I didn't read closely, and that's a fresh rebuild with a new convertor. Disregard my comment, sorry.


2011 Toyota Camry, base, 2.5L/6MT, 205k, hers
2010 Toyota Tundra DC, 4.6L/6AT, 159k, ours
1999 Toyota Camry LE, 2.2L/4AT, 225k, his
Re: Chevy 4l80 lockup won't stay locked [Re: Weldlife207] #5422008 05/05/20 08:05 PM
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Sounds like a wore out TCC Regulator Valve Bore, Assuming everything else is sound? Sonnax 34994-01K is a drop-in replacement & fixes 90% of worn valve bodies I've ran across.

A sipping 4th/OD clutch can also set P0894, The ISS sensor reads the Forward Drum NOT the Input/Turbine Shaft!.....So that leaves the TCC & the 4th Clutch between the Flexplate & Forward Drum. I've seen sheared off 4th Clutch Housing bolts cause this code. But your description doesn't lead me to believe you have this issue.

A PCM or Brake Switch failure is unlikely given the P0894, Checking the output of the TCC PWM Solenoid control circuit is never a bad strategy, But likely a waste of time.

When the TCC Regulator Valve wears out the bore.....The TCC Signal oil will leak to the exhaust porting (Arrow), The hotter the fluid gets, The worse the leak becomes!

[Linked Image from i.imgur.com]


2001 Chevy Camaro L92/4L80E
2006 Chevy 2500HD LBZ/Allison 1000
2010 Toyota Corolla 2ZR-FE/U341E
2000 Toyota Avalon 1MZ-FE/A541E
Re: Chevy 4l80 lockup won't stay locked [Re: supton] #5422420 05/06/20 08:46 AM
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Weldlife207 Offline OP
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4l80s aren't a overdrive transmission. They are a 4 spd with lockup

Re: Chevy 4l80 lockup won't stay locked [Re: clinebarger] #5422425 05/06/20 08:49 AM
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Weldlife207 Offline OP
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thanks for the info. Yea the hotter it gets the worse. This sounds like it could be my problem. I've got a bunch of valve bodies ill try another one just to see what it does.

Re: Chevy 4l80 lockup won't stay locked [Re: Weldlife207] #5422440 05/06/20 08:57 AM
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zrxkawboy Offline
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Originally Posted by Weldlife207
4l80s aren't a overdrive transmission. They are a 4 spd with lockup


Yes, it has OD. This link lists the gear ratios:
http://www.novak-adapt.com/knowledge/transmissions/automatic/4l80e


"Think of all the Ford owners who will someday want an automobile." John Dodge

Re: Chevy 4l80 lockup won't stay locked [Re: Weldlife207] #5422442 05/06/20 08:58 AM
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Originally Posted by Weldlife207
4l80s aren't a overdrive transmission. They are a 4 spd with lockup


???

4th is 0.75 . That's overdrive....

Re: Chevy 4l80 lockup won't stay locked [Re: zrxkawboy] #5422443 05/06/20 08:58 AM
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Weldlife207 Offline OP
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The problem was there before the rebuild. I rebuilt the trans along with the valve body with new valves. Then put new torque converter in it.

Re: Chevy 4l80 lockup won't stay locked [Re: zrxkawboy] #5422444 05/06/20 09:00 AM
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Weldlife207 Offline OP
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Could fooled me. I don't see overdrive in the shift indicator. I see some trucks do but not mine.

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