Fresh rebuilt 4L80e Slips in forward and reverse
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Teching In
Joined: Oct 2022
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Probably a dumb question, But are you used to a 3000 stall., It will feel like slipping till you get to around 3000 rpm in any gear position. The line rise seems pretty normal and the drop and back up as you move through gears.
The whine does it only happen when trans still in first gear? or all shifted gears 2-3-4 .
4l80e planets can be noisy in first gear and if you got one with straight cut really noisy.
The whine does it only happen when trans still in first gear? or all shifted gears 2-3-4 .
4l80e planets can be noisy in first gear and if you got one with straight cut really noisy.
Last edited by TravRMK800; Dec 27, 2022 at 10:40 AM. Reason: entered more info
Thread Starter
Teching In
Joined: Oct 2022
Posts: 11
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We tried it with the gear selector in all positions. It does it in 1st and reverse. I don't think I can try actual 2nd, 3rd, or 4th since I believe in 2,3,and 4 it starts out in 1st gear. Maybe there is a way to put it in 2nd with HP tuners in the diag section. I am not sure on that though.
It could be a converter. My issue is you said it slips forward and reverse two very different hydraulic circuits, But line pressure looks normal in both . No commonality exist between fwd and reverse in first gear position hydraulics and reverse , Nor any clutch applications. The OVERDRIVE sprag does have to hold in both so it's a possibility.
Right now reading over all you have posted and checked Im leaning towards either the converter or OD sprag not holding. More to the converter because in MANUAL 1 the overrun clutch should be on taking sprag out of the equation. You could try using scan tool to apply converter clutch this would effectively bypass the converter and see what you end up with. If you do lock converter with scan tool to test also have it in 2nd gear commanded.
Right now reading over all you have posted and checked Im leaning towards either the converter or OD sprag not holding. More to the converter because in MANUAL 1 the overrun clutch should be on taking sprag out of the equation. You could try using scan tool to apply converter clutch this would effectively bypass the converter and see what you end up with. If you do lock converter with scan tool to test also have it in 2nd gear commanded.
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Thread Starter
Teching In
Joined: Oct 2022
Posts: 11
Likes: 1
It could be a converter. My issue is you said it slips forward and reverse two very different hydraulic circuits, But line pressure looks normal in both . No commonality exist between fwd and reverse in first gear position hydraulics and reverse , Nor any clutch applications. The OVERDRIVE sprag does have to hold in both so it's a possibility.
Right now reading over all you have posted and checked Im leaning towards either the converter or OD sprag not holding. More to the converter because in MANUAL 1 the overrun clutch should be on taking sprag out of the equation. You could try using scan tool to apply converter clutch this would effectively bypass the converter and see what you end up with. If you do lock converter with scan tool to test also have it in 2nd gear commanded.
Right now reading over all you have posted and checked Im leaning towards either the converter or OD sprag not holding. More to the converter because in MANUAL 1 the overrun clutch should be on taking sprag out of the equation. You could try using scan tool to apply converter clutch this would effectively bypass the converter and see what you end up with. If you do lock converter with scan tool to test also have it in 2nd gear commanded.
It is a brand-new Circle D billet converter. Hmmm. Sounds like a bad out-of-the-box converter eh?
Yes would tend to point to converter and a converter can cause whine. But if slipping stops with it locked then that is where I would go. Circle D is a good company and I am sure will work well with you on it.
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can you post a copy of your current tune? I have had a couple customers this last year with mismatched OS segment swaps causing issues not totally different than what youre describing.
