: Hard Shifting 4L80E
w_huisman 03-09-2005, 09:00 AM Last night after pulling our new boat home (100 miles, 1600lb) my burb was shifting hard, and hitting second gear especially hard.
My tranny fluid looks and smells like new, and my bro-in-law (a transmission rebuilder for a living) had previously said its in good shape.
After parking it last night, I thought about it as I was falling asleep. "What if it's electrical? It's the only thing that makes sense." This morning I decided to take it to work and wouldn't you know it, it's shifting just like normal again. Before I left for work, let it idle for 10 minutes, then drove 4 blocks to the fueling station, filled up, then took it for a 5 mile road trip out in the country before heading to the office. The whole time it acted like nothing ever happened.
Any ideas?
quantum mechanic 03-09-2005, 09:30 AM My manual says:
harsh shifts
Line pressure-----------too high, too low
force motor--------------failed, off
loose connector
PCM loose connector
accumulator piston--------Leaking, stuck
accumulator spring-------- incorrect
chechballs-----------------incorrect
calibration in prom----------incorrect
Any codes?
w_huisman 03-09-2005, 09:32 AM The check engine light never came on. Does the computer store codes without the check engine light coming on? I can easily enough go check.
quantum mechanic 03-09-2005, 09:38 AM On the tranny, yes.
Check , clear, check again. The hard codes are the one's still there.
w_huisman 03-09-2005, 10:04 AM Before clearing the codes I pulled 73, 81, 82, 83, 84, 87, 99. Now I'll go disconnect the batteries for a while and recheck for codes. Do I have to fire the engine up after clearing the old codes before checking for hard codes?
DTC 73 - Pressure Control Solenoid Circuit (Current Error)
DTC 81 - 2-3 Shift Solenoid Circuit Fault
DTC 82 - 1-2 Shift Solenoid Circuit Fault
DTC 83 - TCC PWM Solenoid Circuit Fault
DTC 84 - Accelerator Pedal Position Circuit Fault
DTC 87 - High Ratio Error
DTC 99 - Accelerator Pedal Position 2 (5 Volt Reference Fault)
nvmtnlion 03-09-2005, 10:37 AM No, to clear codes, while in diag mode (jumpered) press both the accellerator and brake pedal to the floor for a couple seconds and release. That should clear stored codes.
w_huisman 03-09-2005, 10:56 AM After clearing codes, nothing but a flashing 12 before startup. After startup and a 4 mile drive, still nothing but a 12.
PS: I know code 12 means there are no diagnostic codes stored and is only an indicator of being in diagnostic mode. ;)
nvmtnlion 03-09-2005, 12:17 PM 12 is good. 12 means everthing is working.
qci6.5 03-09-2005, 07:20 PM not sure if this is your problem but ...I all of a sudden started getting really hard 1-2 shifts......turned out to be the vehicle speed sensor.Replaced it and it was fine after that.
w_huisman 03-10-2005, 12:01 AM not sure if this is your problem but ...I all of a sudden started getting really hard 1-2 shifts......turned out to be the vehicle speed sensor.Replaced it and it was fine after that.Do the codes listed above point to that?
I was thinking it sounded more like some solenoids on the transmission are headed south. Lupey just replaced something like that not too long ago. Does that sound possible Lupey?
Anyone else wanna try and help me diagnose instead of guess?
Or maybe I should just call it a fluke and leave it at that?:help:
GMCSID 03-10-2005, 12:10 AM 81, 82 and 83 set together would indicate a loss of 12v to the trans. Those components are powered by the same circuit and grounded seperately at the ECM. Possibly a bad connection or bad ignition switch.
lupey6.5 03-10-2005, 01:02 AM Input and output speed sensors are what I replaced. At $30 each they are cheap noninvasive things to try. Mine would shift poorly and get stuck in 2nd until I would shut it down and restart then it would act right for a few minutes to a few days.
quantum mechanic 03-10-2005, 10:11 PM Replace both speed sensors. On 4wd the input is on the tranny, the output is on the tailshaft of the transfercase. I just spent $1000 rebuilding mine but I knew it had problems 75,000 miles ago, do the math on that.
w_huisman 03-11-2005, 08:50 AM Replace both speed sensors. On 4wd the input is on the tranny, the output is on the tailshaft of the transfercase. I just spent $1000 rebuilding mine but I knew it had problems 75,000 miles ago, do the math on that.Good to hear from you QM. I was starting to worry. :D
After doing the math based on your statement, I've calculated that my tranny has many more reliable miles left in it.
Anybody have the GM part numbers handy?
quantum mechanic 03-11-2005, 08:55 AM I'm putting it back in today. Right after I finish my honey do's.
w_huisman 03-11-2005, 09:03 AM Sounds like fun!
You wouldn't have a link to parts site that sells those litte sensors, would you? I'm looking for part numbers, or some other way to verify that the dealer gives me the right parts.
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