Failing automatic transmission or something else?

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A misfire is generally worse when the Converter Clutch locks-up, Lock-up happens at high speeds than when your symptoms are happening. The 4L60E has 2 "Mechanical Diodes"/"One Way Clutches". The Lo/Reverse Roller Clutch & the Input Sprag. When taking off in 1st gear with the Shifter in D4, Your relying on BOTH too hold ALL the input torque. The Input Sprag is MUCH weaker than the Lo/Reverse Roller Clutch. The next time the symptoms come up, Pull into D2 (This allows the Overrun Clutches too come "On" & bypass the Input Sprag), If the symptoms go away AND it's repeatable.....D2=no shutter.....D4= shutter, The Input Sprag is about too FAIL! If the symptoms persist, Pull in down into D1, This Bypasses BOTH L/R Roller Clutch & Input Sprag, If the symptom now disappear.....The Lo/Reverse Roller Clutch has a issue.
 

TurboFiat124

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Originally Posted By: clinebarger
A misfire is generally worse when the Converter Clutch locks-up, Lock-up happens at high speeds than when your symptoms are happening. The 4L60E has 2 "Mechanical Diodes"/"One Way Clutches". The Lo/Reverse Roller Clutch & the Input Sprag. When taking off in 1st gear with the Shifter in D4, Your relying on BOTH too hold ALL the input torque. The Input Sprag is MUCH weaker than the Lo/Reverse Roller Clutch. The next time the symptoms come up, Pull into D2 (This allows the Overrun Clutches too come "On" & bypass the Input Sprag), If the symptoms go away AND it's repeatable.....D2=no shutter.....D4= shutter, The Input Sprag is about too FAIL! If the symptoms persist, Pull in down into D1, This Bypasses BOTH L/R Roller Clutch & Input Sprag, If the symptom now disappear.....The Lo/Reverse Roller Clutch has a issue.
I will give it a shot. Thanks. I'm hoping that a new filter is what the transmission needs. I'm not going to drive it until I get a chance to replace the filter next week. It would be great if the transmission had a drain plug (have not checked). That way I could replace half of the fluid when replacing the filter, then change the fluid again with my next oil change. And maybe a third time just for good measure. According to Ebay there is a drain plug on the 4L60e transmission.
 

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I have never had a drain, many don't -. (Some vehicles have special clearance pans). You can get a B&M drain plug (no welding) - it will strand a small amount by being raised. I tossed the nylon washers and used copper crush washers - more reliable ...
 
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Originally Posted By: Hokiefyd
[quote=TurboFiat124]A mechanic at the Chevrolet dealership actually told me these transmissions were robust but GM front wheel drive automatics were junk because they won't last more than 100,000 miles.
Both of those are gross generalizations. I think some years of the 4L60-E had problems with sun gears or torque converters, right? Seems to be an issue that can come up on Astros and S-10s of this era also. 3 transmissions (sun gear) failed on my GMC Sierra. When the third one went I traded it in. It had 328,500 miles on it. Fluid and filter changed every 30K.
 

TurboFiat124

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Here is an update: Yesterday I changed the automatic transmission filter Fuel filter (while I was under there) air cleaner The hardest part (other than getting covered in transmission fluid) was getting the old filter seal out of the transmission. It requires a small chisel and hammer to remove (destroy) it and a 19mm socket, extension and hammer to drive it back in. If I had to do it over again, I would just re-use the old seal. I noticed a little bit of black sludge in the pan but not that much. I did not find any chunks of friction material in the filter or large chunks of metal attached to the magnet in the pan. Just microscopic grain like pieces but not allot. Allot smaller than what I usually find on magnet drain plugs on manual gearboxes. I gave it a good cleaning in my part washer. One issue was identifying what filter this transmission takes so I had to remove the filter and take it into the auto parts store before buying a new one. There is a shallow and deep pan on this transmission. I think the later is a heavy duty version of this transmission which I have. I also installed a drain plug in the pan. This maybe overkill but my plan is to dump the fluid after about 500 to 1000 miles and add fresh fluid. Then repeat if the fluid still looks a bit dark until the fluid looks a clean red on the dipstick. The fluid I drained out looks black in a pan, but if there is a skim on it on something, it still has a red tint to it. In other words the fluid doesn't look burnt like what the fluid in my wife's Buick's transmission shortly before it gave up the ghost, just full of microscopic friction material. OK the weird thing. The van seems allot quieter now! It was not making a growling or grinding sound before. I can actually hear a slight exhaust leak now that I could not hear before! Perhaps the old fluid lost some of it's viscosity and the new fluid has made it quieter? Also seems to shift between 1st and reverse smoother. Does all of that sound logical after a fluid and filter change? Or am I just expecting to see results? I test drove the van and all seems fine. It shifts fine and so far have not heard any clunks or shutter when taking off from a dead stop. I would think if one of the sprags was going bad, it might do it all the time. Not just every now and then. Hopefully a new filter was what it needed all along. Wish me luck!
 
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