2001 Chevy Astro/GMC Safari - Rear Wheel Drive only (Same platform & drive-train as Chevy S10 and many other Chevy/GMC lightweight trucks/vans).
4.3L Vortec paired with a 3rd gen 4L60e automatic transmission.
Symptom:
- Suddenly lost all forward or reverse movement from the transmission with NO abnormal sounds or warning.
Troubleshooting Verifies:
- Fluid Levels are correct.
- Electrical connections good.
- Mechanical linkage to the transmission are good.
Observations:
- When rear wheels are off ground, rear tires move as expected but when vehicle is on ground, it won't move.
My suspicions:
- Possible loss of hydraulic pressure (Failed transmission pump) OR
- Possible loss of input shaft?
- Clogged filter? (Can that really prevent the vehicle from moving at all?)
Could a clogged filter cause a sudden loss of power to the wheels? I'm all prepped up to drop the transmission but i really, really, really don't want to. BTW, i'm not a mechanic. Just a software developer who's too cheap to pay anyone else to "fix" my cars. I would rather learn and do it myself.
SOLVED. The filter had fallen and wasn't secured in place anymore.
Transmission working fine. I really, really, really hope others find this before they drop and replace the transmission or have it rebuilt without having inspected the contents of the pan.
This solution may apply to ANY transmission using a filter that has an integrated oil pickup tube.
Throttle position sensor may be? Usually the 4l60e just shits itself ro death with loud breaking sounds.
@biggestrichcranium
Excellent alternative suggestion to "Rebuild or Replace" transmission! In all my research, nobody else pointed this out as a possibility. But this suggestion leads me to more questions:
I was not aware that transmissions expect some sort of signal from a Throttle Position Sensor via the ECU. I only understood that the transmission is only needing to be physically linked to the column or floor gear shifter for a mechanically switched model and are physically connected via a torque converter and transmission's input shaft.
With that said, is there something else these transmissions are expecting before they will allow the vehicle to "move"?
Steps I am taking while I await further answer(s):
Verifying the Throttle Position Sensor is working and within factory specifications.
I had a tps go on a silverado,
pulling off in 1st was fine but it used to bang into 2nd at about 2500rpm!
I think you would still have 1st and reverse if it was tps, but I could be wrong.
I'd try and get a line pressure reading somehow.
I did an upvote to the other answer because I had not even thought of the line pressure test.
Could be your torque converter also.
Could a torque converter suddenly and silently fail? With no warning at all?
One thing to note is that when the wheels are off the ground, they DO go forward or reverse and speed up instantly when i step on the accelerator pedal. This is why i do not suspect a failed torque converter. But i am not an expert, which is why I am here.
Well not always, you often get a shuddering or possibly a whine like a bad PS pump. If you get drive when the vehicle is raised up with no load but not when on the ground then it could be a pressure problem caused by tc or pump. If you have a blocked filter then my guess is you have bigger problems. How does the fluid look and smell? Any codes? Might be worth dropping the pan and seeing if you have any debris.
Dropped the pan and the fluid is dark, has a faint smell of having been burnt however,the fluid is free of any particles or debris.
But, i'm thinking that the filter laying on the bottom of the pan might be why i lost hydraulic pressure. (The filter has an integrated oil pickup tube).
Purchased a new filter kit and Dextron-vi fluid today and will be finishing this tomorrow afternoon. I suspect the vehicle should work after that. I will update this tread.
I wasted hours upon hours researching the "no movement" suddenly problem with NO information pointing to possible dropped filter (filter has pickup tube integrated). Apparently when you search for "transmission filter fell symptoms" you do in fact get "vehicle not moving" as the symptom. You just have to know what the problem is to find the symptom but not the other way around.
While i don't know if this fixes my problem or not, i'm almost 99.9% certain this was the culprit. Filter was not secured and fell to the bottom of the pan while driving. No check engine light. No sound was made. Just that the vehicle stopped moving.
I will confirm here if this was the issue. I can't seem to find any info about the "clip" that secures the filter. Not sure how it's held in place.
4l60e filter is just held in by its o ring. Surprised it just fell out unless it hadn't been installed correctly. There are two types, a deep pan and shallow pan one. Make sure you have the correct one.
Lots of times the filter stem rubber seal gasket gets stuck inside the housing on a 4L60. Make sure to pull it out before putting the new filter in. The plastic filter neck can crack if the gasket is doubled up, the pan is bolted in and puts excessive pressure on the neck and it will fail.
