Quote:
Originally Posted by Half-Inch Stud
My inspection of a failed 4L80 and TH400 cores (oh and I am unsure if they lost 2nd, 3rd or both) would reveal a crapped-out Center-Support bushing. Mostly Chevy truck cores, sometimes a Pontiac core. Low-fluid level will lose 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 co-worker 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 rear most Planetaries went Nuclear and reverted to weld fragments. Ya know, that fella wanted as much reused parts as possible because he is a Jeep guy. (it's a JEEP thing) So, I restored the drums and Center Support, but for sure anything to do with the Planetary section was replaced.
The 4L80 is all together and waiting installation in to an on/off road JEEP.
The FWD pack is fed through 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 Center Support determines 2nd Gear, Fed via the Center Support MOUNT.
Study of fluid passages is one think, yet the study of the "3-or-4" Center Support Seal rings running off-concentric on the Direct Pack- Center Support sleeving reveals great concern to all involved.
You know, some Racers and Street folk describe a vibration in Drive at 60 mph or so, or the top-end, big-end of the track and I think that can traced back to a Direct Pack + FWD Pack running untrue relative to the Center Support via the Bushing Clearance. The Bushing Clearence went from slip-fit to 10 or 20 mils out of True Concentricity. Exciting times are prevented by the loss of Fluid Pressure to the Direct Pack to encourage a rebuild.
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I took the liberty to Edit your post for my own benefit because this type of information is Golden to me and I need to absorb it into my limited Transmission Mind in order to correctly repair my Trans.
Mikes answer to this: Had I known as much now as then, when I destroyed my Torque Converter, plus if I knew it was the T.C that was affected then, I would have driven home in what seemed to be second gear and dismantled the Trans. right away.
The problem is I knew nothing in the beginning. So, I drive 300 more miles testing and tuning while reading all about Transmission 101. Now, I fear the worst in that after reading your posts, I damaged Hard Parts within the Trans. Well, I will have to see, I will give some time to see if any one local will build my Trans. but I am not holding my breath waiting for him.
Currently, I have the main rebuild kit and I am waiting for four more additional parts, that did not come in the main kit that are needed to rebuild this TH 400. The weather up North is slowing down deliveries or so I am told by UPS.
In the meantime, your valuable input, will give me an idea of what to look for while were into this Trans. So, thank you for all your advice and if anyone has any more input, I am all ears. Mike out.