4L80E overdrive sprag failure. No reverse no drive.
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- čas přidán 6. 09. 2024
- The cam lobes in the first clip seem to be the problem. They just weren’t tall enough for the sprag to properly engage on them. This was a brand new sprag so there isn’t roller wear. You could bench test this and it would work correctly but every so often you could get the sprag to get stuck in this position and have it rotate both directions.
The next clip is of the older style sprag and cam lobes.
Look up p/n: 34580K on whatever it takes transmissions website. It’s a complete older style sprag and planet. They are much stronger and will not suffer this failure. This is what you’re after if you get parts from a junkyard trans.
I just finished overhauling and installing a 2003 4L80e. I did the Sonnex upgrades. I don't have reverse or drive. Only 3, 2, 1 gears work. You can feel it go into reverse and drive, but very little movement of the vehicle with increased RPM in those two gear selections. I'm going to lean towards this overrun roller clutch as being the culprit. Thanks for the video!
Yes. It’s very likely the issue. You will see in the beginning of the video that the OD planetary is able to turn both directions. It only should spin one way. Something is happening with the sprag. The earlier 01 and down style is much less likely to have this problem.
After removing the pump and input shaft assembly with the overrun clutch and planetary, that was exactly what my problem was. The planetary assembly would turn in both directions. The funny thing is when I disassemble all of the parts, I can see nothing wrong with any of them. The roller sprague assembly is intact, not broken, not melted. The bore in the planetary assembly isn't obviously worn. Nor are the cam lobes on the hub. And to complicate things even more, I can reassemble all of these parts and it will lock in the clockwise rotation just like it's supposed to...sometimes but not every time, thus making it an intermittent problem! This makes it very difficult for the rookie rebuilder like me to identify bad parts when reassembling this transmission. It's simply not cost effective to replace everything when rebuilding these things, including all of the hard parts. But in this case, I have purchased a complete overrun clutch assembly including the hub, the planetary assembly and the roller sprague. I don't want to remove this transmission a 4th time and tear it apart again! The ATSG manuals do not have service wear limits for transmission components. Maybe they should! This would take the guess work out of the rebuilding process. Wear limits for such things as bushings and the shafts that ride in those bushings, the bores where the seal rings ride, or the cam height and the bores for these one-way sprague's. I'm more on an engine rebuilder than a transmission rebuilder. Every engine out there has service wear limits for such things as cylinder bore, piston diameter, rod and main journals etc. Why not for automatic transmissions I wonder? OK, enough ranting out of me!
@@user-bv1sn2wm8lhow did it go
Would a this cause a slight whine in reverse and in OD?
Not sure. I didn’t have a whine with this issue. Whining can be from the pump, a converter issue, or planetary gears as far as I understand.
Do you think it’s better to use the old design before 2001 ?
Yes. Way stronger and way less likely to break. But if you’re going to really beat on the car (burnouts, high hp pulls, etc.) put the trans into third gear and then you will avoid physically breaking this part.