jcwren
Newbie
I recently acquired a '99 C3500 HD, and it's got the 4L80E with the drum brake. It's leaking a fair amount of ATF from what appears to be the extension housing tail shaft, into the drum brake housing. It's hard to tell for sure since there's so much fluid all over the bottom of the truck. The previous owner told me they had swapped the 4L80E (don't know what happened to the original), and they got frustrated when it started blowing ATF. It's from a tree cutting service, and has a chip box on it, and they didn't have time to mess with it.
I've pulled the driveshaft and the extension housing. It has two bearings in it, and they appear to be lubricated by a passage from the transmission that puts ATF into the bearing housing closest to the transmission, and then I assume just fills the housing with fluid. I don't see where there's a return passage, so maybe it's not circulated, or maybe I just don't know what I'm looking at. This is my first experience with the 4L80E.
The output shaft seal looked OK, but it was hard to get a good look at it, and frankly I had to wreck it to get it out. The O-ring between the transmission and extension housing looks fine. After removing the extension housing, it looks like the output seal on the transmission is weeping (maybe a lot more when the transmission is turning), but if the extension housing does fill with fluid, would that even be an issue? The bearings seem OK. I cleaned up the housing in the parts washer then hosed out the bearings, and they turn freely with very little wobble.
The yoke does have a rough area on it, as you can see in the picture. I'm not sure if taking that down with emery paper may end up removing too much material. Perhaps I should have it welded up and turned down to spec if need be (trying to find a replacement yoke seems next to impossible and the one I did find the person wanted waaay too much for. If you have one you don't want that's in better shape, I'd cheerfully pay shipping and some beer money ).
I am going to replace the transmission output seal unless the wise people here say there's no need, and of course replace the housing o-ring (because I already bought one) and the extension housing output seal. Is there anything else I should look for that may be causing the leak, like the extension housing getting pressurized? I have not yet checked the vent line, it started raining before I could get to that.
Hoping that someone here has some experience with these, and maybe knows of a common issue or a simple fix.
Thanks!
I've pulled the driveshaft and the extension housing. It has two bearings in it, and they appear to be lubricated by a passage from the transmission that puts ATF into the bearing housing closest to the transmission, and then I assume just fills the housing with fluid. I don't see where there's a return passage, so maybe it's not circulated, or maybe I just don't know what I'm looking at. This is my first experience with the 4L80E.
The output shaft seal looked OK, but it was hard to get a good look at it, and frankly I had to wreck it to get it out. The O-ring between the transmission and extension housing looks fine. After removing the extension housing, it looks like the output seal on the transmission is weeping (maybe a lot more when the transmission is turning), but if the extension housing does fill with fluid, would that even be an issue? The bearings seem OK. I cleaned up the housing in the parts washer then hosed out the bearings, and they turn freely with very little wobble.
The yoke does have a rough area on it, as you can see in the picture. I'm not sure if taking that down with emery paper may end up removing too much material. Perhaps I should have it welded up and turned down to spec if need be (trying to find a replacement yoke seems next to impossible and the one I did find the person wanted waaay too much for. If you have one you don't want that's in better shape, I'd cheerfully pay shipping and some beer money ).
I am going to replace the transmission output seal unless the wise people here say there's no need, and of course replace the housing o-ring (because I already bought one) and the extension housing output seal. Is there anything else I should look for that may be causing the leak, like the extension housing getting pressurized? I have not yet checked the vent line, it started raining before I could get to that.
Hoping that someone here has some experience with these, and maybe knows of a common issue or a simple fix.
Thanks!
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