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4L80E Tranny - no over drive, no slipping, no codes everything else drives fine

@FireCaptain05 welcome to TTS..glad you joined and nice rig you got there..she's pretty...
@Grisley1958 is getting you started on the right track...we have a couple of transmission experts on here that will chime in in no time. Just be patient..
You might want to start your own thread about your truck and the problem your having because you posted your stuff on a already existing thread. But that's not a big deal..
Stick around we have a great bunch of guys on here
And again welcome...
 
Grumoly said:
Shop 2
No Codes. Took for a test drive and no overdrive. figures it needs a rebuild. cant be solenoids or wouldnt just loose overdrive. something about a sprag clutch siezed on maybe. - all from a 10 minute drive.
Click to expand...

:banghead: This isn't going to be fun. It should have a ratio error and code if it requested and is not getting OD. Who says the old ECM is any good. It's a Primitive Damn Stupid computer that may not code for some problems even after going into limp mode.

Have you checked and/or adjusted the TPS? This is a GIGO situation that puts it into a harsh shifting limp mode and locks out OD. BTW Adjust your idle speeds on the DB2 THEN adjust the TPS. And remember to do it after adjusting idle speed...

I would also inspect the engine RPM sensor. I can only guess what your year has. Generally it's where the distributor would be on a 454 and is the oil pump drive. See if it's top has cracked and wire condition.

More or less you have Engine RPM sensor, brake switch for TCC cut out, TPS on the DB2, trans input speed sensor, and output speed sensor. Loose any of the sensors and it's Limp Mode time with NO Overdrive. If something slips in the trans instant Limp Mode and No OD. (The Torque converter can slip and the ECM will unlock it and relock it rapidly with no codes and no limp mode.)

The second day I had my 1993 it blew OD with a "BOOM!" like a muffler exploding and hitting the pavement. The sprag failed or a bearing failed first (they couldn't tell what failed first) and stuff went through the OD gears. It ran very hot after that with 3 gears till I took it into the shop for a rebuild. I vote shop #2 as they appear to be clear on "it's not solenoids".

I would manually shift it from 1 - OD and count the four shifts. Tap the brakes and watch the tach or "feel" if the Torque Converter Clutch is unlocking as this can feel like a shift.

FWIW just lifting off the throttle will kick out the TCC as 4L80E are known to shear the input shaft if the TCC stays locked. Any speed under 45 MPH the TCC does not lock.
 
I got my transmission pressure gauge from Harbor freight. You should see at least 50lbs. at an idle, 75-100lbs. In reverse. Once you start moving you should see transmission pressure go up as more pressure is against the vehicle momentum. Mine will run 50 to 150 driving depending on the load. You could have an electrical issue but if it's been run at low pressure it's most likely going to need rebuilt. I have a permanent gauge installed in one of my trucks that I had to change the transmission on and I'm planning on it for the other two also. In my opinion every automatic transmission should have a pressure gauge as long as the driver knew what to look for on it. It would show problems before it ruined the transmission.
 
Its an electronically controlled transmission. First place to start is scan data to see if the PCM is commanding 4th gear or not. If its not commanding it then you need to look and sensor data and see what is preventing it from commanding 4th gear. If its commanding 4th gear but not physically shifting into 4th then you more that likely have an internal issue in the trans. At that point pull it and have it rebuilt.
 
Electrical issues can lead to mechanical failures. If the pressures are good it's probably electrical, but if the pressures are low and it's electrical it has already cause internal damage. You can chase electrical issues till the cows come home, but a pressure test puts you in the right direction.
 
The 4l80 was known for OD clutch issues (roller clutch) and wear in the valve body bore for 4th gear (especially the later 80s). Yours sounds like a valve body issue to me.

An electronic issue will usually affect two gears since it only uses two shift solenoids. That's why you need to confirm PCM command of 4th gear before you go any farther.
 
This might help you, as you can see by the apply chart the only thing that can cause a 4th gear only issues is the 4th gear clutch or a valve body issue that controls the 4th gear clutch. If I remember correctly Sunnax has a repair kit for the AFV valve bore that causes loss of 4ht gear.

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Rockabillyrat said:
This might help you, as you can see by the apply chart the only thing that can cause a 4th gear only issues is the 4th gear clutch or a valve body issue that controls the 4th gear clutch. If I remember correctly Sunnax has a repair kit for the AFV valve bore that causes loss of 4ht gear.

View attachment 68267
Click to expand...
I believe you mean AFL(actuator feed limit) valve. It controls the pressure that the valve body uses to control the trans and lubes the rear bushing in 97+ units. It will cause all kinds of issues, not just loss of OD. Most builders prefer the Transgo valve as it is a larger valve that eliminates the side loading and wear issue. The Sonnax valve uses a sleeve which decreases the valve size and reduces flow which can be a problem on 97+ units that use AFL fluid for lube.
 
THEFERMANATOR said:
I believe you mean AFL(actuator feed limit) valve. It controls the pressure that the valve body uses to control the trans and lubes the rear bushing in 97+ units. It will cause all kinds of issues, not just loss of OD. Most builders prefer the Transgo valve as it is a larger valve that eliminates the side loading and wear issue. The Sonnax valve uses a sleeve which decreases the valve size and reduces flow which can be a problem on 97+ units that use AFL fluid for lube.
Click to expand...
I had to get the 4L60E in My 93 K1500 rebuilt one time, many years ago, a shop in Citrus Heights California did the work.
Before assembling the transmission they bored out the rifling that was feeding the rear bushing, planetaries and OD unit. That is what caused the failure to begin with. The owner of Red D transmission said He was surprised that the previous rebuilder had not done that when they did the rebuild.
 
THEFERMANATOR said:
I believe you mean AFL(actuator feed limit) valve. It controls the pressure that the valve body uses to control the trans and lubes the rear bushing in 97+ units. It will cause all kinds of issues, not just loss of OD. Most builders prefer the Transgo valve as it is a larger valve that eliminates the side loading and wear issue. The Sonnax valve uses a sleeve which decreases the valve size and reduces flow which can be a problem on 97+ units that use AFL fluid for lube.
Click to expand...

Thats the one!
Most people prefer the transgo kit because it's easier to install. The sonnax kit reams the hole larger to fit the sleeve. So I dont think the valve is much smaller if any at all. IMO an anodized sleeve is a better repair. But I'm not transmission expert. My experience with sleeves is with the DB2 advance piston bore. The ONLY way to properly fix that issue.
 
First thing to check with the 4L80E when such an issue arises...

The transmission harness connector on the side of the transmission. They are known to crack internally allowing fluid into the connector which in turn will cause all sorts of weird shift/ing issues just as this OPs issue.

Other things that can cause odd shift issues...

1. Fluid level
2. TCC solenoid issue
3. VSS issue
4. TPS issue
5. CTS issue
6. MAP issue
7. Brake switch
8. Ignition switch (base of steering column)
 
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