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I was going to ask this in my turbo build thread, but I figured I would start a new thread to keep it organized, and I wanted to ask here given I think there is a lot more technical knowledge here even though this is an issue with a stock transmission.
Anyway, I think I am going to have to put my turbo build way way on hold. I put my truck into reverse to pull out of the driveway and it was just kind of sitting there and felt like the emergency brake was on. I put it back in drive then reverse again and it worked, so I drove on down the road and came to a stop to make a right turn and when I went to go it revved up a little bit then went into gear, I can now hear a whirring noise in first and reverse only. Once it shifts to second it stops.
Looking around it seems I have found forum posts with a similar issue, and someone said something about something going wrong in the solenoids or servos and it trying to engage 1st and reverse at the same time. Funny thing is they said their symptoms happened about a month after they did a fluid and filter change and I did one about a month ago as well. I still don't believe in the you shouldn't change fluid becuase it will introduce contaminates old timer advice though.
Anyone have any similar 6L80 issues? The whirring noise in first and reverse is pretty scary sounding, its not overly loud but its noticeable with no AC on and all windows rolled down. I am thinking about trying to find a spare 6L80 to drop in and then try to go through mine for the experience and still be able to use the truck especially if I end up butchering my original transmission.
I guess first thing I can drop the pan again and see if there is any obvious metal or chunks in it, this is a picture when I dropped it about a month ago, everything seemed normal and no signs of excessive torque converter clutch material or metal since that is a supposedly common problem with these:
So I am not a transmission expert, but I do know a little. After thinking about it and listening to the noise a little more. I think it may have something to do with the lo/reverse overrun clutch/sprag clutch. I know the 6L80 is a clutch to clutch shifting transmission but I know it has a overrun clutch for first gear so the first to second gear shift will be theoretically smoother since the transmission just has to let off or apply just one clutch instead of 2 simultaneously. However, trying to read up more about it I keep finding info about it saying there is another clutch I think that holds the lo/reverse sprag on but it comes on at like 2 mph, which would correspond with the symptom I had when it first started with me coming to a stop to turn right and then getting on the gas again and it slipping and revving up a little before engaging and going forward.
That being said it still is weird how this just started randomly out of nowhere, if splines or gears, or the little finger things on the sprag clutch were worn or damaged, I would think I would have gradually started hearing this noise. Also since it revved up and slipped at the stop light and I put it in reverse and it wouldn't go, it would seem like something is wrong hydraulically.
There used to be a guy on the forums named JamesB I think was his username, I wish he was still around. He knew so much about transmissions and I would love reading his posts about the way they shift and shift quality and stuff.
Was it the snap ring that requires the huge pliers that look like limb pruners?
Also I assume the reason you never hear of 6L80 to 6L90 swaps is because it must not be worth it or either you would have to have your ECM and TCM flashed to a different VIN number with a 6L90 and in turn would screw up more stuff.
Yes swapping the 6 speeds requires some TCM flashing and a bunch of gay stuff
Yeah I realize even if I swapped valve body/techm I would have to program it to my vin unless who ever is selling it does it and I wouldn't mind paying for a short tis web subscription to do it. But to actually put a 90 in I think you would have to flash the ECM and Techm to a 8L90 vin I would assume. I don't think the BCM or other modules care only the ecm.
Anyway, looking around at wrecked pullouts and junkyard 80s or 90s seems they want way too much money for them to where I might as well rebuild mine.
I think I am going to drop the pan again and check the valve body for shrinked check ***** which I read is supposedly a problem in high mileage units.
But that being said the noise is what worries me since it sounds mechanical like a bad sprag clutch or either like straight cut gears which makes me think it's a mechanical problem.
But then I'm thinking this might be the usual noise on a 6L80 if the clutch that is supposed to hold the sprag from over running is not applied. I think I read it's supposed to come on around 2mph or so maybe it just makes noise if it doesn't come on and there is a hydraulic reason it's not coming on. This is just my guessing I don't know I'm just hoping.
It detonated itself when snap ring decided to let loose. Truck coasted to a halt, but it made some whirring noise before it let go earlier in the afternoon. I was on it hard in the boost in 4wd in the rain drifting it around a corner when it happened so it destroyed everything. If I was just cruising it might have been a diffrent story. I have now been told snap ring groove wears and let's ring pop out...
Ok thanks, its just so weird to me how everything is still fine and shifting fine its just all the sudden developed a straight cut gear whirring noise.
I've been looking through forum posts trying to find people who have rebuilt 6L80s themselves, I am mainly trying to find out what special tools they had to have and which ones they didn't need. I am just trying to figure out how much I will spend in special tools. I would love to learn to rebuild it myself and I would expect to have to do it once or twice just because there is so many intricacies and right and wrong ways to put things together, but I feel like I could get close to the cost of getting it rebuild by someone else after buying all the special tools I need. I should be able to pull it out and put it back in myself though.
Also it makes no sense how re sellers and junkyards are asking $2500 for these transmissions out of wrecked cars some with 200k+, I just don't see why anyone would pay that much for a used one when you could pay someone to rebuild it for that price, or honestly you can buy a reman for $2500, I don't get it? I must be missing something there, or its just apart of the covid apocalypse supply chain catastrophe excuse.
09-28-2021, 08:01 PM
6L80 Whirring Noise Issues in First and Reverse
