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I have a 2000 model old style Chevy 3/4 ton with 350 engine and 4l80E transmission. Truck has 80K and transmission was serviced at 60K by GM dealer.
My transmission works properly in all gears on level roads. On a hill it will kick out of OD, it will not shift back to OD when the road levels out. When this happens, the shifts from 1 to 2 to 3 are harsh or jerky shifts not as normal. I can turn engine off for 15 seconds, then restart engine and transmission works fine, until I get to the next hill.
Have had codes checked by local auto parts stores, not GM dealership, but so far no defect codes are noted, also no engine service light has come on.
Could this be the cause of my transmission OD problem?
To prevent the OD from burning out (from constant 3-OD up and downshifting and straining the OD) when towing something under load, the trans will force itself out of OD into 3rd when it detects that the converter is not locking up, The factory converter has an internal clutch that controls the lockup of the torque converter, and this clutch's torque capacity is minimal. Hence, if the clutch is going bad, just the weight of the truck and torque required to pull it will force the TCC to unlock the converter and a downshift to 3rd will occur. It will soon be time to replace the converter.
Note: DTC 83 - Torque Converter Clutch
I HAVE A 96 CAD.deville with a fwd 4l80e trans it went bad i bought a replacement for it. it still dont work. a frend told me i got a bad one so it was replaced again. the car still dont move any ideas???
Fred, 1st check your brake light switch. If the switch is out of adjustment or going bad and makes contact, it will unlock the torque. The trans will not stay in overdrive if the torque will not lock. It's the first thing we used to check on an overdrive problem and the simplest to fix. Rich
Hello, I have a 95 G3500 GMC and I have the same problem. I found that the throttle position sensor (on the side of my injector pump) is the possible problem along with the computer going into limp mode when I floor the pedal for passing speed. All I do is sycle the ignition switch three times and it resets the computer and the shift problem goes away until If I only press the pedal 3/4 of the way to the floor it seems to be ok. I haven't tried another TPS because it cost a hundred bucks and I'm not sure if it will cure the problem. As long as I know what to do to keep it shifting i'm going to leave it that way. Gil
Problem is a busted piston in torque converter.
Hard to believe this transmission would go out for that at 80K. I would have thought that the 4L80E was a stronger transmission. As this one has been service properly and never used to pull over 6000# and did that rarely.
Just my luck to buy a truck with weak transmission.
Guess I will look at the Dodge diesel with manual transmission next time.
Exact same issue....replaced all speed sensors, shift sensors, tcc sensor, throttle position sensor, had the trans flushed and new filters with no improvement. Some times it will go 150 miles of interstate driving in OD and then drop out all of a sudden, especially when I have to hit the brake and then resume cruise control. My local dealer just wants to put a transmission in it but I have taken this truck from Maine to Florida and back with no issue (except the OD shift which we are discussing. If it is as simple as a brake light switch I will be happy and yet angry at the same time for wasting all my time and money.
I have a 91 C3500 dually with 7.4 and 4L80E. On a flat and level road about 65+ mph the Converter will momentarily kick out and right back in. There's no check engine light and no pattern. I replaced the TPS for a former prob lem and this problem started up. Any suggestions?? Thanks.
Torque Converter lockup problem finally went away-----I hope!! I replaced the throttle position sensor that I had installed earlier and so far it hasn't kicked in and out of converter lockup. Evidently the first one I bought was defective....who knows. It never showed a check engine light.
email Fred T. Hart Jr.
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