Quote:
Originally Posted by TRADERMIKE 2012
I plan on R+R-Ing all the Bushings, while I am in there, "why is that particular area your diagnostic"? So, I can learn something please. Mike out.
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My inspection of failed 4L80 and TH400 cores (oh and am unsure if they lost 2nd, 3rd or both) would reveal a clapped-out Center-Support bushing. Mostly Chevy truck cores, sometimes a Pontiac core. Low-fluid level will loose 3rd (or mush up 2-3 upshift) so just know that.
Story: Some fella's Chevy truck/van with a 4L80 lost drive ( maybe 2nd too), and drove 1/2 hour home. It failed spectacularly near the home and the 4L80 was sold to a coworker who asked me to go through it. Could be a JEEP enthusiast..read on.
Well, the FWD & Direct Drums were cooked black, the Center-support cooked, and the rearmost Planetaries went nuclear and reverted to weld fragments. Ya know, the fella wanted as much reused as possible because he is a Jeep guy, (it's a JEEP thing) so i restored the drums, center support, but for sure anything to do with the planetary section was replaced.
The 4L80 is all together and waiting install to an on/offroad JEEP.
FWD pack is fed thru the Front Pump and determines being out of Neutral, thus Drive.
Direct Pack determines 3rd gear, and Reverse. Fed via the Center-Support seal rings.
Intermediate Pack within the CenterSupport determines 2nd Gear, Fed via the Center Support MOUNT.
Study of fluid passages is one tingk, yet the study of the "3-or-4" CenSupport Seal rings running off-concentric on the DirectPack- CenterSupport sleeving reveals great concern to all involved.
You know, some racers and Street folks describe a vibration in drive at 60 mph or so, or the top-end, big-end of the track, and i tink that can trace back to a Direct Pack + FWD Pack running untrue relative to the Center Support via the bushing clearance went from slip-fit to 10 or 20 mils. Exciting times are prevented by the loss of fluid pressure to the Direct Pack to encourage a rebuild.