95 GMC K2500 4L80e trans, eng.350
Does not shift. It has Reverse and FWD, however it doesn't appear to have more than 2 and 3. Could this be a Velocity Sensor or worse? I just completed a fluid filter change with hopes of this being the cause. Not the case
VSS is still good if you have your cruise control and speedometer working, it's common for the wire harness to the solenoid on the passenger side to get corroded and or the sires to break due to the heat given off from the catalytic converter beside the transmission. Check the condition of the wire harness and clean the contacts with brake cleaner and reinstall with some grease to keep the corrosion away, hint use marine grease. Marine grease cost a few cents more but resist water longer and better then normal lutetium grease, I use it on everything and get longer life out of my u-joints and front end suspension. Most transmission shop will test drive free of charge and scan the truck for DTC codes that sometimes will not show up in the check engine light, but mostly you do have an electrical problem so check all your fuses and wire harness from the ECM to the transmission. Good luck and keep me posted, be glad to help you get your truck running 100% again soon without some transmission shop getting you to replace the whole transmission for $2,300. If you are going to have the transmission service, "fluid and filter changed" Have them replace your boost valve. The boost valve is around $45.00, the boost valve controls the amount of transmission fluid pressure and low transmission fluid pressure will cause the transmission to fail. I replace mine every second transmission service and i have over 365,000 miles on mine. Keep up the good work friend.
Testimonial: "Excellent information from the beginning.Thank you.I worked each of the connections I could locate and disc. the bat to clear the code. Good so far. "
code 81 Transmission 2-3 shift solenoid voltage stayed high for 2 seconds after
commanded ON by PCM, or the voltage stayed at zero for 2 seconds after commanded
OFF by PCM.
Check the Solenoid wire harness for any damages causing a ground, if wire check's out good. Then check the solenoid voltage and function of the solenoid. Oh and sorry the wire harness is on the drivers side, my bad. Divers side towards the tail end, Good luck and keep me posted.
Great job, most transmission shop would have told you you need a new transmission. If your going to get the transmission serviced, have then replace the boost valve. Replacing the boost valve every 100,000 miles or less will make your transmission last a life time, as long as there is no hard parts break in the transmission. The boost valve regulate the transmission line pressure which controls the firmness of the shift, and the boost valve springs weaken due to mileage and heat. The line pressure drops and the amount of pressure on the clutch pack drops causing them to start to slip when the transmission changes from gear to gear. The boost valve is easy to replace and coast an average of $50.00, but the transmission pan needs to be dropped so your better waiting till you get the transmission serviced since it's only an extra 5 min to replace it. Good luck friend and you may want to spray some anti corrosion spray to the transmission connectors like the ones used on battery post.
×
I think for your description its a gearbox remnoval at the minimum for repair.
5,789 views
Usually answered in minutes!
Molson02536
The Check Engine Light is not on, do you believe it could still be electrical? Thanks for the detailed list.
By the way I did removed the VSS there were a few particles stuck to it, but it was not chewed. Does it sound like it is still good?
I got an 81 code. Struggling to find all of the harnesses and connectors as you described. Didn't find anything near the CAT conv.
Any tips..ha.
I guess I should drop the pan again and check the solenoids???
I got an 81 code. Struggling to find all of the harnesses and connectors as you described. Didn't find anything near the CAT conv.
Any tips..ha.
I guess I should drop the pan again and check the solenoids???
Dec 20, 2009
- I got an 81 code. Struggling to find all of the harnesses and connectors as you described. Didn't find anything near the CAT conv. Any tips..ha. I guess I should drop the pan again and check the solenoids???
Molson02536,
Thank you for all of your help. Disconnected and reconnected all plugs I could reach and the cleared the code by disconnecting the battery for 15 secs. I could tell the difference as soon as I pulled it out of the garage.
If it is a fluke, I will keep you posted, but thank you, you saved me some big money!!!
It sounds like your transmission is in limp mode. What is "limp-home mode" ? This is a fault mode in which the
transmission either loses electrical power or the PCM deactivates all
of the electronics. The transmission will default to max line pressure.
The driver will have Reverse and 3rd, with manual 2nd available by
putting the gearshift in 2 or 1 (doesn't matter). 1st, 4th, and TCC
lockup will not be available. It will not hurt the car to drive it like
this for short periods, but use manual 2nd to get the car moving, and
be aware that the trans will generate more heat than normal while
operating in limp-home mode due to increased torque converter slippage
during 2nd gear starts and no lockup in 3rd gear. Trans shifts into gear harshly, car feels sluggish off the line,
No 1st, 4th or TCC lockup available, Manual 2nd, 3rd and Reverse are
only available gears, CEL is on: Transmission is either in limp-home
mode or has lost electrical power. If there are lots of error codes in
the PCM, check the under hood fuse that powers the transmission, and if
it pops again, look for a short in that circuit like an O2 sensor
harness touching exhaust. Otherwise, check PCM codes for a particular
fault in the transmission causing the PCM to put it in limp-home mode. No 1st or 4th available; trans shifts 2nd to 3rd by itself in D or OD and locks the converter : ShiftA solenoid failed. Easy fix in the pan. Or a wiring problem from PCM to trans.. or PCM. Car goes into gear but feels very sluggish like the brakes are dragging,
but it will roll easily (starts out in 4th gear), you manually shift to
2 to get it moving, once it's moving you put it back in OD and the car
shifts 3rd to 4th on its own and locks the converter at the appropriate
time: ShiftB solenoid failed: Easy fix in the pan. Or a wiring problem
from PCM to trans.. or PCM. Transmission does not shift automatically, only manually. Swap in a known-good PCM, check wiring, check other sensors such as VSS and TPS. 3rd gear starts, can manually shift through all gears. When car has
been turned off for a bit, then back on it will run normally.: VSS drop off w/ Hi-stall converter. The rpms are too high, but VSS is
showing no movement. Happens after a tire burning take-off. Doesn't
store a code, will not throw a CEL (I've heard that it will store a
code if it happens 3 or more times). Cure: Reprogram PCM for VSS drop off -- PCMforLess knows about it. These are the most common things to look for in the 4L80E, start with the transmission fuse and work your way to the wire harness and connector clips from the transmission to the PCM. The solenoid wire harness is located on the passenger side, it's common for that clip to corrode causing the limp mode. Simple fix which many shady transmission shop calls for and new transmission and replacing the Boost valve when servicing the transmission which is a $45.00 part will make your transmission last a lift time. Hope this helps and keep me posted, be glad to know you got your truck running 100% again soon.
×